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\input texinfo
@c $Id: latex2e.texi 710 2018-10-14 14:32:52Z karl $
@comment %**start of header (This is for running Texinfo on a region.)
@setfilename latex2e.info
@set UPDATED October 2018
@include common.texi
@settitle @LaTeX{}2e unofficial reference manual (@value{UPDATED})
@comment %**end of header (This is for running Texinfo on a region.)

@c latex 2.09 commands should all be present now,
@c xx but latex2e stuff is missing.
@c xx random list of a few of the missing items is at the end of this file
@c
@c xx ctan, distributions, components of TeX
@c xx classes and packages -- required, additional, useful; oberdiek; fonts
@c
@c xx merge permuted-index
@c xx merge latex-manual from savannah
@c xx merge display style math
@c xx JH explain nfss somewhere
@c xx JH expand BiBTeX
@c xx JH expand theorem, AMS math
@c xx JH something on code listings
@c xx JH ligatures
@c xx JH \xspace
@c xx JH \stretch
@c xx JH \mathstrut
@c xx JH \phantom https://tex.stackexchange.com/questions/4519/how-do-i-create-an-invisible-character
@c xx JH \baselineskip https://texfaq.org/FAQ-baselinepar
@c xx JH \contentsline, \@@dottedtocline?
@c xx JH more on \write18, beyond what's mentioned in Command line.
@c xx JH \numexpr, \dimexpr, \glueexpr, \muexpr
@c
@c xx The typeset source2e has an index with all kernel
@c xx commands, though some are internal and shouldn't be included.
@c xx classes.dtx et al. define additional commands.
@c xx See also http://ctan.org/pkg/macros2e.

@copying
This document is an unofficial reference manual for @LaTeX{}, a
document preparation system, version of @value{UPDATED}.

This manual was originally translated from @file{LATEX.HLP} v1.0a in the
VMS Help Library.  The pre-translation version was written by
George@tie{}D. Greenwade of Sam Houston State University.  The
@LaTeX{}@tie{}2.09 version was written by Stephen Gilmore.  The
@LaTeX{}2e version was adapted from this by Torsten Martinsen.  Karl
Berry made further updates and additions, and gratefully acknowledges
using @cite{Hypertext Help with @LaTeX{}}, by Sheldon Green, and
@cite{@LaTeX{} Command Summary} (for @LaTeX{}@tie{}2.09) by
L.@tie{}Botway and C.@tie{}Biemesderfer (published by the @TeX{} Users
Group as @cite{@TeX{}niques} number 10), as reference material.  We also
gratefully acknowledge additional material appearing in
latex2e-reference by Martin Herbert Dietze.  (From these references no
text was directly copied.)

Copyright 2007, 2008, 2009, 2010, 2011, 2012, 2013,
2014, 2015, 2016, 2017, 2018 Karl Berry.@*
Copyright 1988, 1994, 2007 Stephen Gilmore.@*
Copyright 1994, 1995, 1996 Torsten Martinsen.

@comment start of License
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).
@end ignore

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions.
@comment end of License
@end copying

@c Merge into one index (arbitrarily chosen to be the concept index).
@syncodeindex fn cp

@dircategory TeX
@direntry
* LaTeX2e: (latex2e).              Unofficial LaTeX reference manual.
@end direntry

@tex
\global\hbadness=4444 % don't complain much
@end tex

@titlepage
@title @LaTeX{}2e: An unofficial reference manual
@subtitle @value{UPDATED}
@author @url{@value{LTXREFMAN_HOME_PAGE}}
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@shortcontents
@contents

@c Best Effort Symbol
@iftex
@macro BES {utf8,math}
@math{\math\}
@end macro
@macro BESU {utf8,math}
@code{@backslashchar{}\math\}
@end macro
@end iftex
@ifnottex
@macro BES {utf8,math}
@U{\utf8\}
@end macro
@macro BESU {utf8,math}
@U{\utf8\}
@end macro
@end ifnottex
@macro EnvIndex {env}
@findex @r{environment}, @code{\env\}
@findex @code{\env\} @r{environment}
        
@end macro
@macro PkgIndex {pkg}
@cindex @r{package}, @code{\pkg\}
@cindex @code{\pkg\} @r{package}

@end macro

@set NotInPlainTeX Not available in plain @TeX{}.
@set NeedsAMSSymb @value{NotInPlainTeX} In @LaTeX{} you need to load the @file{amssymb} package.
@set NeedsSTIX @value{NotInPlainTeX} In @LaTeX{} you need to load the @file{stix} package.

@node Top
@top @LaTeX{}2e: An unofficial reference manual

This document is an unofficial reference manual (version of
@value{UPDATED}) for @LaTeX{}2e, a document preparation system.

@menu
* About this document::         Bug reporting, etc.
* Overview::                    What is @LaTeX{}?
* Document classes::		Some of the various classes available.
* Fonts::			Italic, bold, typewriter, etc.
* Layout::			Controlling the page layout.
* Sectioning::			Parts, Chapters, Sections, etc.
* Cross references::		Automatic referencing.
* Environments::		Such as enumerate & itemize.
* Line breaking::	        Influencing line breaks.
* Page breaking::	        Influencing page breaks.
* Footnotes::			How to produce footnotes.
* Definitions::			Define your own commands, etc.
* Counters::			Internal counters used by @LaTeX{}.
* Lengths::			The length commands.
* Making paragraphs::		Paragraph commands.
* Math formulas::		How to create mathematical formulas.
* Modes::			Paragraph, Math or LR modes.
* Page styles::			Various styles of page layout.
* Spaces::		        Horizontal and vertical space.
* Boxes::                       Making boxes.
* Color::                       Defining and using colors.
* Graphics::                    Importing graphics from outside @LaTeX{}.
* Special insertions::		Inserting reserved and special characters.
* Splitting the input::		Dealing with big files by splitting.
* Front/back matter::		Tables of contents, glossaries, indexes.
* Letters::			The @code{letter} class.
* Terminal input/output::	User interaction.
* Command line::                System-independent command-line behavior.
* Document templates::          Starter templates for various document classes.
* Index::		        General index.
@end menu


@node About this document
@chapter About this document

@cindex home page for manual
This is an unofficial reference manual for the @LaTeX{}2e document
preparation system, which is a macro package for the @TeX{}
typesetting program (@pxref{Overview}).

This document's home page is @url{@value{LTXREFMAN_HOME_PAGE}}.  There
you can get the sources, subscribe to the mailing list or read its
archives, see other infrastructure, and get the current output in
various formats.  In particular, the output comes in two web formats.
Probably the most convenient one, shown at @url{http://latexref.xyz/},
has pages for each topic and so is good for a quick lookup; see also the
note there about easy-to-remember links.  The other, shown at
@url{http://svn.gnu.org.ua/viewvc/latexrefman/trunk/latex2e.html?view=co},
has all the information on single page.

@cindex @LaTeX{} vs.@: @LaTeX{}2e
In this document, we will mostly just use `@LaTeX{}' rather than
`@LaTeX{}2e', since the previous version of @LaTeX{}@tie{}(2.09) was
frozen decades ago.

@cindex unofficial nature of this manual
@cindex @LaTeX{} Project team
@findex @email{@value{LTXREFMAN_BUGS}} @r{email address}
@LaTeX{} is currently maintained by a group of volunteers
(@url{http://latex-project.org}).  The official documentation written by
the @LaTeX{} project is available from their web site.  This document is
completely unofficial and has not been reviewed by the @LaTeX{}
maintainers.  
@cindex bug reporting
@cindex reporting bugs
Do not send bug reports or anything else about this document to them.
Instead, please send all comments to @email{@value{LTXREFMAN_BUGS}}.

This document is a reference.  There is a vast array of other sources
of information about @LaTeX{}, at all levels.  Here are a few
introductions.

@table @url
@item http://ctan.org/pkg/latex-doc-ptr
@findex latex-doc-ptr @r{document}
Two pages of recommended references to @LaTeX{} documentation.

@item http://ctan.org/pkg/first-latex-doc
@findex first-latex-doc @r{document}
Writing your first document, with a bit of both text and math.

@item http://ctan.org/pkg/usrguide
@findex usrguide @r{official documentation}
The guide for document authors that is maintained as part of @LaTeX{}.
Many other guides by many other people are also available, independent
of @LaTeX{} itself; one such is the next item:

@item http://ctan.org/pkg/lshort
@findex lshort @r{document}
A short introduction to @LaTeX{}, translated to many languages.

@item http://tug.org/begin.html
Introduction to the @TeX{} system, including @LaTeX{}, with further
references.

@end table


@node Overview
@chapter Overview of @LaTeX{}

@cindex overview of @LaTeX{}
@cindex basics of @LaTeX{}
@cindex Knuth, Donald E.
@cindex Lamport, Leslie
@cindex @LaTeX{} overview

@LaTeX{} is a system for typesetting documents.  It was originally
created by Leslie Lamport and is now maintained by a group of volunteers
(@url{http://latex-project.org}).  It is widely used, particularly for
complex and technical documents, such as those involving mathematics.

@cindex macro package, @LaTeX{} as
A @LaTeX{} user writes an input file containing text along with
interspersed commands, for instance commands describing how the text
should be formatted.  It is implemented as a set of related commands
that interface with Donald@tie{}E. Knuth's @TeX{} typesetting program
(the technical term is that @LaTeX{} is a @dfn{macro package} for the
@TeX{} engine).  The user produces the output document by giving that
input file to the @TeX{} engine.

The term @LaTeX{} is also sometimes used to mean the language in which
the document is marked up, that is, to mean the set of commands
available to a @LaTeX{} user.

@cindex Lamport @TeX{}
@cindex pronunciation
The name @LaTeX{} is short for ``Lamport @TeX{}''.  It is pronounced
LAH-teck or LAY-teck, or sometimes LAY-tecks.  Inside a document,
produce the logo with @code{\LaTeX}.  Where use of the logo is not
sensible, such as in plain text, write it as @samp{LaTeX}.

@menu
* Starting and ending::     The standard beginning and end of a document.
* Output files::            Files produced.
* @TeX{} engines::          Programs that can compile @TeX{} and  @LaTeX{}.
* @LaTeX{} command syntax:: General syntax of @LaTeX{} commands.
* Environment::             Area of the source giving distinct behavior.
* CTAN::                    Our repository.
@end menu


@node Starting and ending
@section Starting and ending

@anchor{Starting & ending}@c old name
@cindex starting and ending
@cindex ending and starting
@cindex hello, world

@LaTeX{} files have a simple global structure, with a standard beginning
and ending.  This is a small example.

@example
\documentclass@{article@}
\begin@{document@}
Hello, \LaTeX\ world.
\end@{document@}
@end example

@noindent
Every @LaTeX{} document has a @code{\begin@{document@}} line and an
@code{\end@{document@}} line.

@cindex document class, defined
@noindent
Here, the @samp{article} is the @dfn{document class}.  It is implemented
in a file @file{article.cls}.  You can use any document class on your
system.  A few document classes are defined by @LaTeX{} itself, and vast
array of others are widely available.  @xref{Document classes}.

@cindex preamble, defined
You can include other @LaTeX{} commands between the
@code{\documentclass} and the @code{\begin@{document@}} commands.
This area is called the @dfn{preamble}.

The @code{\begin@{document@}}, @code{\end@{document@}} pair defines an
@cindex environment
@dfn{environment}; the @samp{document} environment (and no others) is
required in all @LaTeX{} documents (@pxref{document}).  @LaTeX{} make
available to you many environments that are documented here
(@pxref{Environments}).  Many more are available to you from external
packages, most importantly those available at CTAN (@pxref{CTAN}).

The following sections discuss how to produce PDF or other output from
a @LaTeX{} input file.


@node Output files
@section Output files

@LaTeX{} produces a main output file and at least two auxiliary files.
The main output file's name ends in either @file{.dvi} or @file{.pdf}.

@table @code
@item .dvi
@findex .dvi @r{file}
@findex latex @r{command}
@findex xdvi @r{command}
@findex dvips @r{command}
@findex dvipdfmx @r{command}
@findex dvitype @r{command}
@anchor{output files dvi}
If @LaTeX{} is invoked with the system command @command{latex} then it
produces a DeVice Independent file, with extension @file{.dvi}.  You
can view this file with a command such as @command{xdvi}, or convert
it to a PostScript @code{.ps} file with @command{dvips} or to a
Portable Document Format @code{.pdf} file with @command{dvipdfmx}.
The contents of the file can be dumped in human-readable form with
@command{dvitype}.  A vast array of other DVI utility programs are
available (@url{http://mirror.ctan.org/dviware}).

@item .pdf
@findex .pdf @r{file}
@cindex pdf@TeX{}
@findex pdflatex @r{command}
@anchor{output files pdf}
If @LaTeX{} is invoked via the system command @command{pdflatex},
among other commands (@pxref{@TeX{} engines}), then the main output is
a Portable Document Format (PDF) file.  Typically this is a
self-contained file, with all fonts and images included.

@end table

@LaTeX{} also produces at least two additional files.

@table @code
@item .log
@cindex transcript file
@cindex log file
@findex .log @r{file}
@anchor{output files log}
This transcript file contains summary information such as a list of
loaded packages.  It also includes diagnostic messages and perhaps
additional information for any errors.

@item .aux
@cindex auxiliary file
@findex .aux @r{file}
@cindex cross references, resolving
@cindex forward references, resolving
@cindex references, resolving forward
@anchor{output files aux}
Auxiliary information is used by @LaTeX{} for things such as
cross references.  For example, the first time that @LaTeX{} finds a
forward reference---a cross reference to something that has not yet
appeared in the source---it will appear in the output as a doubled
question mark @code{??}.  When the referred-to spot does eventually
appear in the source then @LaTeX{} writes its location information to
this @code{.aux} file.  On the next invocation, @LaTeX{} reads the
location information from this file and uses it to resolve the
reference, replacing the double question mark with the remembered
location.

@end table

@findex .lof @r{file}
@cindex list of figures file
@findex .lot @r{file}
@cindex list of tables file
@findex .toc @r{file}
@cindex table of contents file
@cindex contents file
@LaTeX{} may produce yet more files, characterized by the filename
ending.  These include a @code{.lof} file that is used to make a list of
figures, a @code{.lot} file used to make a list of tables, and a
@code{.toc} file used to make a table of contents (@pxref{Table of
contents etc.}).  A particular class may create others; the list is
open-ended.


@node @TeX{} engines
@section @TeX{} engines

@cindex engines, @TeX{}
@cindex implementations of @TeX{}
@cindex UTF-8
@cindex Unicode input, native
@cindex TrueType fonts
@cindex OpenType fonts

@LaTeX{} is defined to be a set of commands that are run by a @TeX{}
implementation (@pxref{Overview}).  This section gives a terse
overview of the main programs (see also@tie{}@ref{Command line}).

@table @code
@item latex
@itemx pdflatex
@cindex pdf@TeX{} engine
@findex etex @r{command}
@cindex e-@TeX{}
@anchor{tex engines latex}
In @TeX{} Live (@url{http://tug.org/texlive}), if @LaTeX{} is invoked
via either the system command @command{latex} or @command{pdflatex},
then the pdf@TeX{} engine is run (@url{http://ctan.org/pkg/pdftex}).
When invoked as @command{latex}, the main output is a @file{.dvi}
file; as @command{pdflatex}, the main output is a @file{.pdf} file.

pdf@TeX{} incorporates the e-@TeX{} extensions to Knuth's original
program (@url{http://ctan.org/pkg/etex}), including additional
programming features and bi-directional typesetting, and has plenty of
extensions of its own.  e-@TeX{} is available on its own as the system
command @command{etex}, but this is plain @TeX{} (and produces
@file{.dvi}).

In other @TeX{} distributions, @command{latex} may invoke e-@TeX{}
rather than pdf@TeX{}.  In any case, the e-@TeX{} extensions can be
assumed to be available in @LaTeX{}.

@item lualatex
@findex lualatex @r{command}
@cindex Lua@TeX{}
@anchor{tex engines lualatex}
If @LaTeX{} is invoked via the system command @command{lualatex}, the
Lua@TeX{} engine is run (@url{http://ctan.org/pkg/luatex}).  This
program allows code written in the scripting language Lua
(@url{http://luatex.org}) to interact with @TeX{}'s typesetting.
Lua@TeX{} handles UTF-8 Unicode input natively, can handle OpenType
and TrueType fonts, and produces a @file{.pdf} file by default.
There is also @command{dvilualatex} to produce a @file{.dvi} file,
but this is rarely used.

@item xelatex
@findex xelatex @r{command}
@cindex Xe@TeX{}
@findex .xdv @r{file}
@findex xdvipdfmx
@anchor{tex engines xelatex}
If @LaTeX{} is invoked with the system command @command{xelatex}, the
Xe@TeX{} engine is run (@url{http://tug.org/xetex}).  Like Lua@TeX{},
Xe@TeX{} natively supports UTF-8 Unicode and TrueType and OpenType
fonts, though the implementation is completely different, mainly using
external libraries instead of internal code.  Xe@TeX{} produces a
@file{.pdf} file as output; it does not support DVI output.

Internally, Xe@TeX{} creates an @code{.xdv} file, a variant of DVI,
and translates that to PDF using the (@code{x})@code{dvipdfmx}
program, but this process is automatic.  The @code{.xdv} file is only
useful for debugging.

@end table

Other variants of @LaTeX{} and @TeX{} exist, e.g., to provide
additional support for Japanese and other languages ([u]p@TeX{},
@url{http://ctan.org/pkg/ptex}, @url{http://ctan.org/pkg/uptex}).


@node @LaTeX{} command syntax
@section @LaTeX{} command syntax

@cindex command syntax
@findex \ @r{character starting commands}
@findex [...] @r{for optional arguments}
@findex @{...@} @r{for required arguments}
In the @LaTeX{} input file, a command name starts with a backslash
character, @code{\}.  The name itself then consists of either
(a)@tie{}a string of letters or (b)@tie{}a single non-letter.

@LaTeX{} commands names are case sensitive so that @code{\pagebreak}
differs from @code{\Pagebreak} (the latter is not a standard command).
Most commands are lowercase, but in any event you must enter all
commands in the same case as they are defined.

A command may be followed by zero, one, or more arguments. These
arguments may be either required or optional.  Required arguments are
contained in curly braces, @code{@{...@}}.  Optional arguments are
contained in square brackets, @code{[...]}.  Generally, but not
universally, if the command accepts an optional argument, it comes
first, before any required arguments.

Inside of an optional argument, to use the character close square
bracket@tie{}(@code{]}) hide it inside curly braces, as
in@tie{}@code{\item[closing bracket @{]@}]}.  Similarly, if an optional
argument comes last, with no required argument after it, then to make
the first character of the following text be an open square bracket,
hide it inside curly braces.

Some of @LaTeX{}'s commands are a @dfn{declaration}.  Such a command
changes the value the meaning of some other command or parameter.  For
instance, the @code{\mainmatter} declaration changes the typesetting of
page numbers from roman numerals to arabic (@pxref{\frontmatter &
\mainmatter & \backmatter}).

@LaTeX{} has the convention that some commands have a @code{*} form that
is related to the form without a @code{*}, such as @code{\chapter} and
@code{\chapter*}.  The exact difference in behavior varies from command
to command.

This manual describes all accepted options and @code{*}-forms for the
commands it covers (barring unintentional omissions, a.k.a.@: bugs).


@node Environment
@section Environment

Synopsis:

@example
\begin@{@var{environment name}@}
  ...
\end@{@var{environment name}@}
@end example

An area of @LaTeX{} source, inside of which there is a distinct
behavior.  For instance, for poetry in @LaTeX{} put the lines between
@code{\begin@{verse@}} and @code{\end@{verse@}}.

@example
\begin@{verse@}
  There once was a man from Nantucket \\
  ...
\end@{verse@}
@end example

@xref{Environments} for a list of environments.  Particularly notable is
that every @LaTeX{} document must have a @code{document} environment,
a @code{\begin@{document@} ... \end@{document@}} pair.

The @var{environment name} at the beginning must exactly match that at
the end.  This includes the case where @var{environment name} ends in a
star@tie{}(@code{*}); both the @code{\begin} and @code{\end} texts must
include the star.

Environments may have arguments, including optional arguments.  This
example produces a table.  The first argument is optional (and causes
the table to be aligned on its top row) while the second argument is
required (it specifies the formatting of columns).

@example
\begin@{tabular@}[t]@{r|l@}
  ... rows of table ...
\end@{tabular@}
@end example 


@node CTAN
@section CTAN: the Comprehensive @TeX{} Archive Network

@cindex CTAN

The Comprehensive @TeX{} Archive Network, CTAN, is the @TeX{} and
@LaTeX{} community's repository of free material.  It is a set of
Internet sites around the world that offer material related to @LaTeX{}
for download.  Visit CTAN on the web at @url{https://ctan.org}.

This material is organized into packages, discrete bundles that
typically offer some coherent functionality and are maintained by one
person or a small number of people.  For instance, many publishers have
a package that allows authors to format papers to that publisher's
specifications.

In addition to the massive holdings, the web site offers features such
as search by name or by functionality.

@cindex DANTE e.V.
@cindex mirrors of CTAN
CTAN is not a single site, but instead is a set of sites. One of the
sites is the core. This site actively manages the material, for
instance, by accepting uploads of new or updated packages. It is
hosted by the German @TeX{} group DANTE e.V. Other sites around the
world help out by mirroring, that is, automatically syncing their
collections with the core site and then in turn making their copies
publicly available. This gives users close to their location better
access and relieves the load on the core site. The list of mirrors is
at @url{https://ctan.org/mirrors}.


@node Document classes
@chapter Document classes

@cindex document classes
@cindex classes of documents
@findex \documentclass

The document's overall class is defined with this command, which is
normally the first command in a @LaTeX{} source file.

@example
\documentclass[@var{options}]@{@var{class}@}
@end example

@findex article @r{class}
@findex report @r{class}
@findex book @r{class}
@findex letter @r{class}
@findex slides @r{class}
The following document @var{class} names are built into @LaTeX{}.
(Many other document classes are available as separate packages;
@pxref{Overview}.)

@table @code
@item article
@anchor{document classes article}
For a journal article, a presentation, and miscellaneous general use.

@item book
@anchor{document classes book}
Full-length books, including chapters and possibly including front
matter, such as a preface, and back matter, such as an appendix
(@pxref{Front/back matter}).

@item letter
@anchor{document classes letter}
Mail, optionally including mailing labels 
(@pxref{Letters}).

@item report
@anchor{document classes report}
For documents of length between an @code{article} and a @code{book},
such as technical reports or theses, which may contain several chapters.

@item slides
@anchor{document classes slides}
For slide presentations---rarely used today.  In its place the
@code{beamer} package is perhaps the most prevalent (@pxref{beamer
template}).

@end table

Standard @var{options} are described in the next section.

@menu
* Document class options::   Global options.
* Additional packages::       Bring in packages.
* Class and package construction::   Create new classes and packages.
@end menu


@node Document class options
@section Document class options

@cindex document class options
@cindex options, document class
@cindex class options
@cindex global options

You can specify @dfn{global options} or @dfn{class options} to the
@code{\documentclass} command by enclosing them in square brackets.  To
specify more than one @var{option}, separate them with a comma.

@example
\documentclass[@var{option1},@var{option2},...]@{@var{class}@}
@end example

Here is the list of the standard class options.

@findex 10pt @r{option}
@findex 11pt @r{option}
@findex 12pt @r{option}
All of the standard classes except @code{slides} accept the following
options for selecting the typeface size (default is @code{10pt}):

@example
10pt  11pt  12pt
@end example

@findex a4paper @r{option}
@findex a5paper @r{option}
@findex b5paper @r{option}
@findex executivepaper @r{option}
@findex legalpaper @r{option}
@findex letterpaper @r{option}
All of the standard classes accept these options for selecting the paper
size (these show height by width):

@table @code 
@item a4paper 
210 by 297@dmn{mm} (about 8.25 by 11.75@tie{}inches)

@item a5paper 
148 by 210@dmn{mm} (about 5.8 by 8.3@tie{}inches)

@item b5paper
176 by 250@dmn{mm} (about 6.9 by 9.8@tie{}inches)
 
@item executivepaper
7.25 by 10.5@tie{}inches
 
@item legalpaper
8.5 by 14@tie{}inches
 
@item letterpaper
8.5 by 11@tie{}inches (the default)
@end table

@findex \pdfpagewidth
@findex \pdfpageheight
@PkgIndex{geometry}
When using one of the engines pdf@LaTeX{}, Lua@LaTeX{}, or Xe@LaTeX{}
(@pxref{@TeX{} engines}), options other than @code{letterpaper} set
the print area but you must also set the physical paper size.  One way
to do that is to put @code{\pdfpagewidth=\paperwidth} and
@code{\pdfpageheight=\paperheight} in your document's preamble.
@PkgIndex{geometry}
The @code{geometry} package provides flexible ways of setting the print
area and physical page size.

@findex draft @r{option}
@findex final @r{option}
@findex fleqn @r{option}
@findex landscape @r{option}
@findex leqno @r{option}
@findex openbib @r{option}
@findex titlepage @r{option}
@findex notitlepage @r{option}
Miscellaneous other options:

@table @code
@item draft
@itemx final
@cindex black boxes, omitting
Mark (@code{draft}) or do not mark (@code{final}) overfull boxes with a
black box in the margin; default is @code{final}.

@item fleqn
@cindex flush left equations
@cindex centered equations
@cindex equations, flush left vs.@: centered
Put displayed formulas flush left; default is centered.

@item landscape
@cindex landscape orientation
@cindex portrait orientation
Selects landscape format; default is portrait.

@item leqno
@cindex left-hand equation numbers
@cindex right-hand equation numbers
@cindex equation numbers, left vs.@: right
Put equation numbers on the left side of equations; default is the right side.

@item openbib
@cindex bibliography format, open
Use ``open'' bibliography format.

@item titlepage
@itemx notitlepage
@cindex title page, separate or run-in
Specifies whether there is a separate page for the title information and
for the abstract also, if there is one.  The default for the
@code{report} class is @code{titlepage}, for the other classes it is
@code{notitlepage}.
@end table

The following options are not available with the @code{slides} class.

@findex onecolumn @r{option}
@findex twocolumn @r{option}
@findex oneside @r{option}
@findex twoside @r{option}
@findex openright @r{option}
@findex openany @r{option}
@table @code
@item onecolumn
@itemx twocolumn
Typeset in one or two columns; default is @code{onecolumn}.

@item oneside
@itemx twoside
@findex \evensidemargin
@findex \oddsidemargin
Selects one- or two-sided layout; default is @code{oneside}, except
that in the @code{book} class the default is @code{twoside}.

For one-sided printing, the text is centered on the page.  For two-sided
printing, the @code{\evensidemargin} (@code{\oddsidemargin}) parameter
determines the distance on even (odd) numbered pages between the left
side of the page and the text's left margin, with @code{\oddsidemargin}
being 40% of the difference between @code{\paperwidth} and
@code{\textwidth}, and @code{\evensidemargin} is the remainder.

@item openright
@itemx openany
Determines if a chapter should start on a right-hand page; default is
@code{openright} for @code{book}, and @code{openany} for @code{report}.
@end table

@findex clock @r{option to @code{slides} class}
The @code{slides} class offers the option @code{clock} for printing
the time at the bottom of each note.


@node Additional packages
@section Additional packages

@cindex loading additional packages
@cindex packages, loading additional
@cindex additional packages, loading
@findex \usepackage
Load a package @var{pkg}, with the package options given in the comma-separated
list @var{options}, as here.

@example
\usepackage[@var{options}]@{@var{pkg}@}.
@end example

To specify more than one package you can separate them with a comma,
as in @code{\usepackage@{@var{pkg1},@var{pkg2},...@}}, or use multiple
@code{\usepackage} commands.

@cindex global options
@cindex options, global
Any options given in the @code{\documentclass} command that are unknown
to the selected document class are passed on to the packages loaded with
@code{\usepackage}.


@node Class and package construction
@section Class and package construction

@cindex document class commands
@cindex commands, document class
@cindex new class commands

You can create new document classes and new packages.  For instance, if
your memos must satisfy some local requirements, such as a
standard header for each page, then you could create a new class
@code{smcmemo.cls} and begin your documents with
@code{\documentclass@{smcmemo@}}.

What separates a package from a document class is that the commands in a
package are useful across classes while those in a document class are
specific to that class.  Thus, a command to set page headers is for a
package while a command to make the page headers say @code{Memo from the
SMC Math Department} is for a class.
@cindex class and package difference
@cindex difference between class and package

Inside of a class or package file you can use the at-sign @code{@@} as a
character in command names without having to surround the code
containing that command with @code{\makeatletter} and
@code{\makeatother}.  @xref{\makeatletter & \makeatother}. This allow
you to create commands that users will not accidentally redefine.
Another technique is to preface class- or package-specific commands with
some string to prevent your class or package from interfering with
others. For instance, the class @code{smcmemo} might have commands
@code{\smc@@tolist}, @code{\smc@@fromlist}, etc.


@menu
* Class and package structure::     Layout of the file.
* Class and package commands::      List of commands.
@end menu


@node Class and package structure
@subsection Class and package structure

@cindex class and package structure
@cindex class file layout 
@cindex package file layout 
@cindex options, document class
@cindex options, package
@cindex class options
@cindex package options

A class file or package file typically has four parts.  
@enumerate
@item
In the @dfn{identification part}, the file says that it is a @LaTeX{}
package or class and describes itself, using the @code{\NeedsTeXFormat}
and @code{\ProvidesClass} or @code{\ProvidesPackage} commands.

@item
The @dfn{preliminary declarations part} declares some commands and
can also load other files. Usually these commands will be those needed
for the code used in the next part.  For example, an @code{smcmemo}
class might be called with an option to read in a file with a list of
people for the to-head, as @code{\documentclass[mathto]@{smcmemo@}}, and
therefore needs to define a command
@code{\newcommand@{\setto@}[1]@{\def\@@tolist@{#1@}@}} used in that
file.

@item
In the @dfn{handle options part} the class or package declares
and processes its options.  Class options allow a user to start their
document as @code{\documentclass[@var{option list}]@{@var{class
name}@}}, to modify the behavior of the class.  An example is when you
declare @code{\documentclass[11pt]@{article@}} to set the default
document font size.  

@item
Finally, in the @dfn{more declarations part} the class or package usually does
most of its work: declaring new variables, commands and fonts, and
loading other files.
@end enumerate

Here is a starting class file, which should be saved as @file{stub.cls}
where @LaTeX{} can find it, for example in the same directory as the
@file{.tex} file.

@example
\NeedsTeXFormat@{LaTeX2e@}
\ProvidesClass@{stub@}[2017/07/06 stub to start building classes from]
\DeclareOption*@{\PassOptionsToClass@{\CurrentOption@}@{article@}@}
\ProcessOptions\relax
\LoadClass@{article@}
@end example
@cindex class file example

@noindent
It identifies itself, handles the class options via the default of
passing them all to the @code{article} class, and then loads the
@code{article} class to provide the basis for this class's code.

For more, see the official guide for class and package writers, the
Class Guide, at
@url{http://www.latex-project.org/help/documentation/clsguide.pdf} (much
of the descriptions here derive from this document), or the tutorial
@url{https://www.tug.org/TUGboat/tb26-3/tb84heff.pdf}.


@node Class and package commands
@subsection Class and package commands
@cindex class and package commands
@cindex commands, class and package

These are the commands designed to help writers of classes or packages.

@table @code
@item \AtBeginDvi@{specials@}
@findex \AtBeginDvi
Save in a box register things that are written to the @file{.dvi} file
at the beginning of the shipout of the first page of the document.

@item \AtEndOfClass@{@var{code}@}
@item \AtEndOfPackage@{@var{code}@}
@findex \AtEndOfClass
@findex \AtEndOfPackage
Hook to insert @var{code} to be executed when @LaTeX{} finishes
processing the current class or package.  You can use these hooks
multiple times; the @code{code} will be executed in the order that you
called it.  See also @ref{\AtBeginDocument}.

@item \CheckCommand@{@var{cmd}@}[@var{num}][@var{default}]@{@var{definition}@}
@item \CheckCommand*@{@var{cmd}@}[@var{num}][@var{default}]@{@var{definition}@}
@findex \CheckCommand
@findex \CheckCommand*
@cindex new command, check
Like @code{\newcommand} (@pxref{\newcommand & \renewcommand}) but does
not define @var{cmd}; instead it checks that the current definition of
@var{cmd} is exactly as given by @var{definition} and is or is not 
@cindex long command
@dfn{long} as expected.  A long command is a command that accepts
@code{\par} within an argument.  The @var{cmd} command is expected to be
long with the unstarred version of @code{\CheckCommand}.  Raises an
error when the check fails.  This allows you to check before you start
redefining @code{cmd} yourself that no other package has already
redefined this command.

@item \ClassError@{@var{class name}@}@{@var{error text}@}@{@var{help text}@}
@item \PackageError@{@var{package name}@}@{@var{error text}@}@{@var{help text}@}
@item \ClassWarning@{@var{class name}@}@{@var{warning text}@}
@item \PackageWarning@{@var{package name}@}@{@var{warning text}@}
@item \ClassWarningNoLine@{@var{class name}@}@{@var{warning text}@}
@item \PackageWarningNoLine@{@var{package name}@}@{@var{warning text}@}
@item \ClassInfo@{@var{class name}@}@{@var{info text}@}
@item \PackageInfo@{@var{package name}@}@{@var{info text}@}
@item \ClassInfoNoLine@{@var{class name}@}@{@var{info text}@}
@item \PackageInfoNoLine@{@var{package name}@}@{@var{info text}@}
@findex \ClassError
@findex \PackageError
@findex \ClassWarning
@findex \PackageWarning
@findex \ClassWarningNoLine
@findex \PackageWarningNoLine
@findex \ClassInfo
@findex \PackageInfo
@findex \ClassInfoNoLine
@findex \PackageInfoNoLine
Produce an error message, or warning or informational messages.

For @code{\ClassError} and @code{\PackageError} the message is
@var{error text}, followed by @TeX{}'s @code{?} error prompt. If the
user then asks for help by typing @code{h}, they see the @var{help
text}.

The four warning commands are similar except that they write
@var{warning text} on the screen with no error prompt.  The four info
commands write @var{info text} only in the transcript file.  The
@code{NoLine} versions do not show the number of the line generating the
message, while the other versions do show that number.

To format the messages, including the @var{help text}: use
@code{\protect} to stop a command from expanding, get a line break with
@code{\MessageBreak}, and get a space with @code{\space} when a space
character does not allow it, like after a command.  Note that @LaTeX{}
appends a period to the messages.

@item \CurrentOption
@findex \CurrentOption
Expands to the name of the currently-being-processed option.  Can only
be used within the @var{code} argument of either @code{\DeclareOption}
or @code{\DeclareOption*}.

@item \DeclareOption@{@var{option}@}@{@var{code}@}
@item \DeclareOption*@{@var{code}@}
@findex \DeclareOption
@findex \DeclareOption*
@cindex class options
@cindex package options
@cindex options, class
@cindex options, package
Make an option available to a user to invoke in their
@code{\documentclass} command.  For example, the @code{smcmemo} class
could have an option @code{\documentclass[logo]@{smcmemo@}} allowing
users to put the institutional logo on the first page.  The class file
must contain @code{\DeclareOption@{logo@}@{@var{code}@}} (and later,
@code{\ProcessOptions}).

If you request an option that has not been declared, by default this
will produce a warning like @code{Unused global option(s): [badoption].}
Change this behaviour with the starred version
@code{\DeclareOption*@{@var{code}@}}.  For example, many classes extend
an existing class, using a declaration such as
@code{\LoadClass@{article@}}, and for passing extra options to the
underlying class use code such as this.

@example
\DeclareOption*@{%
\PassOptionsToClass@{\CurrentOption@}@{article@}%
@}
@end example

Another example is that the class @code{smcmemo} may allow users to keep
lists of memo recipients in external files.  Then the user could invoke
@code{\documentclass[math]@{smcmemo@}} and it will read the file
@code{math.memo}.  This code handles the file if it exists and otherwise
passes the option to the @code{article} class.

@example
\DeclareOption*@{\InputIfFileExists@{\CurrentOption.memo@}@{@}@{%
    \PassOptionsToClass@{\CurrentOption@}@{article@}@}@}
@end example

@item \DeclareRobustCommand@{@var{cmd}@}[@var{num}][@var{default}]@{@var{definition}@} 
@item \DeclareRobustCommand*@{@var{cmd}@}[@var{num}][@var{default}]@{@var{definition}@}
@findex \DeclareRobustCommand
@findex \DeclareRobustCommand*
@cindex new command, definition
Like @code{\newcommand} and @code{\newcommand*} (@pxref{\newcommand &
\renewcommand}) but these declare a robust command, even if some code
within the @var{definition} is fragile.  (For a discussion of robust and
fragile commands @pxref{\protect}.) Use this command to define new
robust commands or to redefine existing commands and make them
robust. Unlike @code{\newcommand} these do not give an error if macro
@var{cmd} already exists; instead, a log message is put into the
transcript file if a command is redefined.

Commands defined this way are a bit less efficient than those defined
using @code{\newcommand} so unless the command's data is fragile and the
command is used within a moving argument, use @code{\newcommand}.

@PkgIndex{etoolbox} The @file{etoolbox} package offers the commands
@code{\newrobustcmd}, @code{\newrobustcmd*}, as well as the commands
@code{\renewrobustcmd}, @code{\renewrobustcmd*}, and the commands
@code{\providerobustcmd}, and @code{\providerobustcmd*}.  These are
similar to @code{\newcommand}, @code{\newcommand*},
@code{\renewcommand}, @code{\renewcommand*}, @code{\providecommand}, and
@code{\providecommand*}, but define a robust @var{cmd} with two
advantages as compared to @code{\DeclareRobustCommand}:
@enumerate
@item
They use the low-level e-@TeX{} protection mechanism rather than the
higher level @LaTeX{} @code{\protect} mechanism, so they do not incur
the slight loss of performance mentioned above, and
@item
They make the same distinction between @code{\new@dots{}},
@code{\renew@dots{}}, and @code{\provide@dots{}}, as the standard
commands, so they do not just make a log message when you redefine
@var{cmd} that already exists, in that case you need to use either
@code{\renew@dots{}} or @code{\provide@dots{}} or you get an error.
@end enumerate


@item \IfFileExists@{@var{file name}@}@{@var{true code}@}@{@var{false code}@}
@item \InputIfFileExists@{@var{file name}@}@{@var{true code}@}@{@var{false code}@}
@findex \IfFileExists
@findex \InputIfFileExists
Execute @var{true code} if @LaTeX{} finds the file @file{@var{file
name}} or @var{false code} otherwise.  In the first case it executing
@var{true code} and then inputs the file.  Thus the command

@example
\IfFileExists@{img.pdf@}@{%
  \includegraphics@{img.pdf@}@}@{\typeout@{!! img.pdf not found@}
@end example

@noindent
will include the graphic @file{img.pdf} if it is found and otherwise
give a warning.

This command looks for the file in all search paths that @LaTeX{} uses,
not only in the current directory.  To look only in the current
directory do something like @code{\IfFileExists@{./filename@}@{@var{true
code}@}@{@var{false code}@}}.  If you ask for a filename without a
@code{.tex} extension then @LaTeX{} will first look for the file by
appending the @code{.tex}; for more on how @LaTeX{} handles file
extensions see @ref{\input}.

@item \LoadClass[@var{options list}]@{@var{class name}@}[@var{release date}]
@item \LoadClassWithOptions@{@var{class name}@}[@var{release date}]
@findex \LoadClass
@findex \LoadClassWithOptions
Load a class, as with @code{\documentclass[@var{options
list}]@{@var{class name}@}[@var{release info}]}.  An example is
@code{\LoadClass[twoside]@{article@}}.

The @var{options list}, if present, is a comma-separated list.  The
@var{release date} is optional.  If present it must have the form
@var{YYYY/MM/DD}.
@c BTW, there are at-macros documented in macros2e.pdf to check the version
@c and do some actions conditionnally on version later or not to some
@c date.

If you request a @var{release date} and the date of the package
installed on your system is earlier, then you get a warning on the
screen and in the log like this.

@example
You have requested, on input line 4, version `2038/01/19' of
document class article, but only version `2014/09/29 v1.4h
Standard LaTeX document class' is available.
@end example

The command version @code{\LoadClassWithOptions} uses the list of
options for the current class.  This means it ignores any options passed
to it via @code{\PassOptionsToClass}.  This is a convenience command
that lets you build classes on existing ones, such as the standard
@code{article} class, without having to track which options were passed.

@item \ExecuteOptions@{@var{options-list}@}
@findex \ExecuteOptions
For each option @var{option} in the @var{options-list}, in order, this command
executes the command @code{\ds@@@var{option}}.  If this command is not
defined then that option is silently ignored.

It can be used to provide a default option list before
@code{\ProcessOptions}.  For example, if in a class file you want the
default to be 11pt fonts then you could specify
@code{\ExecuteOptions@{11pt@}\ProcessOptions\relax}.

@item \NeedsTeXFormat@{@var{format}@}[@var{format date}]
@findex \NeedsTeXFormat
Specifies the format that this class must be run under.  Often issued
as the first line of a class file, and most often used as:
@code{\NeedsTeXFormat@{LaTeX2e@}}.  When a document using that class is
processed, the format name given here must match the format that is
actually being run (including that the @var{format} string is case
sensitive).  If it does not match then execution stops with an error
like @samp{This file needs format `LaTeX2e' but this is `xxx'.}

To specify a version of the format that you know to have certain
features, include the optional @var{format date} on which those features
were implemented.  If present it must be in the form @code{YYYY/MM/DD}.
If the format version installed on your system is earlier than
@var{format date} then you get a warning like this.

@example
You have requested release `2038/01/20' of LaTeX, but only
release `2016/02/01' is available.
@end example

@item \OptionNotUsed
@findex \OptionNotUsed
Adds the current option to the list of unused options.  Can only be used
within the @var{code} argument of either @code{\DeclareOption} or
@code{\DeclareOption*}.

@c I cannot reproduce this behavior as it is documented in clsguide.
@c In the absence of a @code{\DeclareOption*} declaration, @LaTeX{} issues
@c on the console a warning like @code{LaTeX Warning: Unused global
@c option(s): [unusedoption].} with the list of not-used options when it
@c reaches @code{\begin@{document@}}.

@item \PassOptionsToClass@{@var{option list}@}@{@var{class name}@}
@item \PassOptionsToPackage@{@var{option list}@}@{@var{package name}@}
@findex \PassOptionsToClass
@findex \PassOptionsToPackage
Adds the options in the comma-separated list @var{option list} to the
options used by any future @code{\RequirePackage} or @code{\usepackage}
command for package @var{package name} or the class @var{class name}.

The reason for these commands is: you may load a package any number of
times with no options but if you want options then you may only supply
them when you first load the package.  Loading a package with options
more than once will get you an error like @code{Option clash for package
foo.} (@LaTeX{} throws an error even if there is no conflict between the
options.)

If your own code is bringing in a package twice then you can collapse
that to once, for example replacing the two
@code{\RequirePackage[landscape]@{geometry@}} and
@code{\RequirePackage[margins=1in]@{geometry@}} with the single command
@code{\RequirePackage[landscape,margins=1in]@{geometry@}}.

However, imagine that you are loading @file{firstpkg} and inside that
package it loads @file{secondpkg}, and you need the second package to be
loaded with option @code{draft}.  Then before doing the first package
you must queue up the options for the second package, like this.

@example
\PassOptionsToPackage@{draft@}@{secondpkg@}
\RequirePackage@{firstpkg@}
@end example

@noindent
(If @code{firstpkg.sty} loads an option in conflict with what you want
then you may have to alter its source.)

These commands are useful for general users as well as class and package
writers.  For instance, suppose a user wants to load the @code{graphicx}
package with the option @code{draft} and also wants to use a class
@code{foo} that loads the @code{graphicx} package, but without that
option. The user could start their @LaTeX{} file with
@code{\PassOptionsToPackage@{draft@}@{graphicx@}\documentclass@{foo@}}.

@item \ProcessOptions
@item \ProcessOptions*@var{\@@options}
@findex \ProcessOptions
@findex \ProcessOptions*
Execute the code for each option that the user has invoked.  Include it
in the class file as @code{\ProcessOptions\relax} (because of the
existence of the starred command).

Options come in two types.  @dfn{Local options} have been specified for this
particular package in the @var{options} argument of
@code{\PassOptionsToPackage@{@var{options}@}},
@code{\usepackage[@var{options}]}, or
@code{\RequirePackage[@var{options}]}.  @dfn{Global options} are those given
by the class user in @code{\documentclass[@var{options}]} (If an option
is specified both locally and globally then it is local.)

When @code{\ProcessOptions} is called for a package @file{pkg.sty}, the
following happens:
@enumerate
@item
For each option @var{option} so far declared
with @code{\DeclareOption}, it looks to see if that option is either a
global or a local option for @code{pkg}. If so then it executes the
declared code.  This is done in the order in which these options were
given in @file{pkg.sty}.
@item
For each remaining local option, it executes the command
@code{\ds@@}@var{option} if it has been defined somewhere (other than by
a @code{\DeclareOption}); otherwise, it executes the default option code
given in @code{\DeclareOption*}. If no default option code has been
declared then it gives an error message.  This is done in the order in
which these options were specified.
@end enumerate

When @code{\ProcessOptions} is called for a class it works in the same
way except that all options are local, and the default @var{code} for
@code{\DeclareOption*} is @code{\OptionNotUsed} rather than an error.

The starred version @code{\ProcessOptions*} executes the
options in the order specified in the calling commands, rather than in
the order of declaration in the class or package. For a package this
means that the global options are processed first.

@item \ProvidesClass@{@var{class name}@}[@var{release date} @var{brief additional information}]
@item \ProvidesClass@{@var{class name}@}[@var{release date}]
@item \ProvidesPackage@{@var{package name}@}[@var{release date} @var{brief additional information}]
@item \ProvidesPackage@{@var{package name}@}[@var{release date}]
@findex \ProvidesClass
@findex \ProvidesPackage
Identifies the class or package, printing a message to the screen and
the log file.

When you load a class or package, for example with
@code{\documentclass@{smcmemo@}} or @code{\usepackage@{test@}}, @LaTeX{}
inputs a file.  If the name of the file does not match the class or
package name declared in it then you get a warning.  Thus, if you invoke
@code{\documentclass@{smcmemo@}}, and the file @file{smcmemo.cls} has
the statement @code{\ProvidesClass@{xxx@}} then you get a warning like
@code{You have requested document class `smcmemo', but the document
class provides 'xxx'.}  This warning does not prevent @LaTeX{} from
processing the rest of the class file normally.

If you include the optional argument then you must include a date,
before any spaces, of the form @code{YYYY/MM/DD}. The rest of the
optional argument is free-form, although it traditionally identifies the
class, and is written to the screen during compilation and to the log
file.  Thus, if your file @file{smcmemo.cls} contains the line
@code{\ProvidesClass@{smcmemo@}[2008/06/01 v1.0 SMC memo class]} and
your document's first line is @code{\documentclass@{smcmemo@}} then you
will see @code{Document Class: smcmemo 2008/06/01 v1.0 SMC memo class}.

The date in the optional argument allows class and package users to ask
to be warned if the version of the class or package is earlier than
@var{release date}.  For instance, a user could enter
@code{\documentclass@{smcmemo@}[2018/10/12]} or
@code{\usepackage@{foo@}[[2017/07/07]]} to require a class or package
with certain features by specifying that it must be released no earlier
than the given date.  (Although, in practice package users only rarely
include a date, and class users almost never do.)

@item \ProvidesFile@{@var{file name}@}[@var{additional information}]
@findex \ProvidesFile
Declare a file other than the main class and package files, such as
configuration files or font definition files.  Put this command in that
file and you get in the log a string like @code{File: test.config
2017/10/12 config file for test.cls} for @var{file name} equal to
@samp{test.config} and @var{additional information} equal to
@samp{2017/10/12 config file for test.cls}.

@item \RequirePackage[@var{option list}]@{@var{package name}@}[@var{release date}]
@item \RequirePackageWithOptions@{@var{package name}@}[@var{release date}]
@findex \RequirePackage
@findex \RequirePackageWithOptions
Load a package, like the command @code{\usepackage} (@pxref{Additional
packages}). The @LaTeX{} development team strongly recommends use of
these commands over Plain@tie{}@TeX{}'s @code{\input}; see the Class
Guide.  An example is
@code{\RequirePackage[landscape,margin=1in]@{geometry@}}.

The @var{option list}, if present, is a comma-separated list.  The
@var{release date}, if present, must have the form @var{YYYY/MM/DD}.  If
the release date of the package as installed on your system is earlier
than @var{release date} then you get a warning like @code{You have
requested, on input line 9, version `2017/07/03' of package jhtest, but
only version `2000/01/01' is available}.

The @code{\RequirePackageWithOptions} version uses the list of options
for the current class.  This means it ignores any options passed to it
via @code{\PassOptionsToClass}.  This is a convenience command to allow
easily building classes on existing ones without having to track which
options were passed.

The difference between @code{\usepackage} and @code{\RequirePackage} is
small.  The @code{\usepackage} command is intended for the document file
while @code{\RequirePackage} is intended for package and class files.
Thus, using @code{\usepackage} before the @code{\documentclass} command
causes @LaTeX{} to give error like @code{\usepackage before
\documentclass}, but you can use @code{\RequirePackage} there.
@end table


@node Fonts
@chapter Fonts
@anchor{Typefaces}@c old name

@cindex typefaces
@cindex fonts

Two important aspects of selecting a @dfn{font} are specifying a size
and a style.  The @LaTeX{} commands for doing this are described here.

@menu
* Font styles::                 Select roman, italics, etc.
* Font sizes::                  Select point size.
* Low-level font commands::     Select encoding, family, series, shape.
@end menu


@node Font styles
@section Font styles

@cindex font styles
@cindex type styles
@cindex styles of text

The following type style commands are supported by @LaTeX{}.

In the table below the listed commands, the @code{\text...}  commands,
is used with an argument, as in @code{\textit@{@var{text}@}}.  This is
the preferred form.  But shown after it, in parenthesis, is the
corresponding declaration form, which is sometimes useful.  This form
takes no arguments, as in @code{@{\itshape @var{text}@}}.  The scope of
the declaration form lasts until the next type style command or the end
of the current group.  In addition, each has an environment form such as
@code{\begin@{itshape@}...\end@{itshape@}}.

These commands, in both the argument form and the declaration form, are
cumulative; for instance you can get bold sans serif by saying either of
@code{\sffamily\bfseries} or @code{\bfseries\sffamily}.

@findex \nocorrlist
@findex \nocorr
One advantage of these commands is that they automatically insert italic
corrections if needed (@pxref{\/}).  Specifically, they insert the
italic correction unless the following character is in the list
@code{\nocorrlist}, which by default consists of a period and a comma.
To suppress the automatic insertion of italic correction, use
@code{\nocorr} at the start or end of the command argument, such as
@code{\textit@{\nocorr text@}} or @code{\textsc@{text \nocorr@}}.

@table @code
@item \textrm (\rmfamily)
@findex \textrm
@findex \rmfamily
Roman.

@item \textit (\itshape)
@findex \textit
@findex \itshape
Italics.

@item \textmd (\mdseries)
@findex \textmd
@findex \mdseries
Medium weight (default).

@item \textbf (\bfseries)
@findex \textbf
@findex \bfseries
Boldface.

@item \textup (\upshape)
@findex \textup
@findex \upshape
Upright (default).

@item \textsl (\slshape)
@findex \textsl
@findex \slshape
Slanted.

@item \textsf (\sffamily)
@findex \textsf
@findex \sffamily
Sans serif.

@item \textsc (\scshape)
@findex \textsc
@findex \scshape
Small caps.

@item \texttt (\ttfamily)
@findex \texttt
@findex \ttfamily
Typewriter.

@item \textnormal (\normalfont)
@findex \textnormal
@findex \normalfont
Main document font.

@end table

@cindex emphasis
@findex \emph
Although it also changes fonts, the @code{\emph@{@var{text}@}} command
is semantic, for text to be emphasized, and should not be used as a
substitute for @code{\textit}.  For example, @code{\emph@{@var{start
text} \emph@{@var{middle text}@} @var{end text}@}} will result in the
@var{start text} and @var{end text} in italics, but @var{middle text}
will be in roman.

@LaTeX{} also provides the following commands, which unconditionally
switch to the given style, that is, are @emph{not} cumulative.  They are
used as declarations: @code{@{\@var{cmd}...@}} instead of
@code{\@var{cmd}@{...@}}.

(The unconditional commands below are an older version of font
switching. The earlier commands are an improvement in most
circumstances. But sometimes an unconditional font switch is precisely
what you want.)

@ftable @code
@item \bf
@cindex bold font
Switch to bold face.

@item \cal
@cindex script letters for math
@cindex calligraphic letters for math
Switch to calligraphic letters for math.

@item \it
@cindex italic font
Italics.

@item \rm
@cindex roman font
Roman.

@item \sc
@cindex small caps font
Small caps.

@item \sf
@cindex sans serif font
Sans serif.

@item \sl
@cindex slanted font
@cindex oblique font
Slanted (oblique).

@item \tt
@cindex typewriter font
@cindex monospace font
@cindex fixed-width font
Typewriter (monospace, fixed-width).

@end ftable

The @code{\em} command is the unconditional version of @code{\emph}.

The following commands are for use in math mode.  They are not
cumulative, so @code{\mathbf@{\mathit@{@var{symbol}@}@}} does not
create a boldface and italic @var{symbol}; instead, it will just be in
italics.  This is because typically math symbols need consistent
typographic treatment, regardless of the surrounding environment.

@table @code
@item \mathrm
@findex \mathrm
Roman, for use in math mode.

@item \mathbf
@findex \mathbf
Boldface, for use in math mode.

@item \mathsf
@findex \mathsf
Sans serif, for use in math mode.

@item \mathtt
@findex \mathtt
Typewriter, for use in math mode.

@item \mathit
@itemx (\mit)
Italics, for use in math mode.

@item \mathnormal
@findex \mathnormal
For use in math mode, e.g., inside another type style declaration.

@item \mathcal
@findex \mathcal
Calligraphic letters, for use in math mode.

@end table

@findex \mathversion
@cindex math, bold
@cindex bold math
In addition, the command @code{\mathversion@{bold@}} can be used for
switching to bold letters and symbols in
formulas. @code{\mathversion@{normal@}} restores the default.

@findex \oldstylenums
@cindex numerals, old-style
@cindex old-style numerals
@cindex lining numerals
@PkgIndex{textcomp}
Finally, the command @code{\oldstylenums@{@var{numerals}@}} will typeset
so-called ``old-style'' numerals, which have differing heights and
depths (and sometimes widths) from the standard ``lining'' numerals,
which all have the same height as uppercase letters.  @LaTeX{}'s
default fonts support this, and will respect @code{\textbf} (but not
other styles; there are no italic old-style numerals in Computer
Modern).  Many other fonts have old-style numerals also; sometimes the
@code{textcomp} package must be loaded, and sometimes package options
are provided to make them the default.  FAQ entry:
@url{http://www.tex.ac.uk/cgi-bin/texfaq2html?label=osf}.


@node Font sizes
@section Font sizes

@cindex font sizes
@cindex typeface sizes
@cindex sizes of text

The following standard type size commands are supported by @LaTeX{}.
The table shows the command name and the corresponding actual font
size used (in points) with the @samp{10pt}, @samp{11pt}, and
@samp{12pt} document size options, respectively (@pxref{Document class
options}).

@findex \tiny
@findex \scriptsize
@findex \footnotesize
@findex \small
@findex \normalsize
@findex \large
@findex \Large
@findex \LARGE
@findex \huge
@findex \Huge

@multitable {@code{\normalsize} (default)@ @ } {24.88@ @ } {24.88@ @ } {24.88}
@headitem Command  @tab @code{10pt}  @tab @code{11pt}  @tab @code{12pt}
@item @code{\tiny}
@tab 5          @tab 6          @tab 6
@item @code{\scriptsize}
@tab 7          @tab 8          @tab 8
@item @code{\footnotesize}
@tab 8          @tab 9          @tab 10
@item @code{\small}
@tab 9          @tab 10         @tab 10.95
@item @code{\normalsize} (default)
@tab 10         @tab 10.95      @tab 12
@item @code{\large}
@tab 12         @tab 12         @tab 14.4
@item @code{\Large}
@tab 14.4       @tab 14.4       @tab 17.28
@item @code{\LARGE}
@tab 17.28      @tab 17.28      @tab 20.74
@item @code{\huge}
@tab 20.74      @tab 20.74      @tab 24.88
@item @code{\Huge}
@tab 24.88      @tab 24.88      @tab 24.88
@end multitable

The commands are listed here in declaration forms. You use them by
declaring them, as with this example.

@example
\begin@{quotation@} \small
  The Tao that can be named is not the eternal Tao.
\end@{quotation@}
@end example

@noindent
The scope of the @code{\small} lasts until the end of the
@code{quotation} environment.  It would also end at the next type style
command or the end of the current group, so you could enclose it in
extra curly braces @code{@{\small We are here, we are here, we are
here!@}}.  You can instead use the environment form of these commands;
for instance, @code{\begin@{tiny@}...\end@{tiny@}}.


@node Low-level font commands
@section Low-level font commands

@cindex low-level font commands
@cindex font commands, low-level

These commands are primarily intended for writers of macros and
packages.  The commands listed here are only a subset of the available
ones.
@c xx but it should be complete
@c xx something about ultimately reading ENCFAM.fd?

@table @code
@anchor{low level font commands fontencoding}
@item \fontencoding@{@var{encoding}@}
@findex \fontencoding
Select the font encoding, the encoding of the output font. There are a
large number of valid encodings.  The most common are @code{OT1},
Knuth's original encoding for Computer Modern (the default), and
@code{T1}, also known as the Cork encoding, which has support for the
accented characters used by the most widespread European languages
(German, French, Italian, Polish and others), which allows @TeX{} to
hyphenate words containing accented letters. For more, see
@url{https://ctan.org/pkg/encguide}.

@anchor{low level font commands fontfamily}
@item \fontfamily@{@var{family}@}
@findex \fontfamily
@cindex families, of fonts
@cindex font catalogue
Select the font family.  The web page
@url{http://www.tug.dk/FontCatalogue/} provides one way to browse
through many of the fonts easily used with @LaTeX{}.  Here are
examples of some common families.

@multitable {font} {Computer Modern Typewriter more space}
@item @code{pag}
@tab Avant Garde
@item @code{fvs}
@tab Bitstream Vera Sans
@item @code{pbk}
@tab Bookman
@item @code{bch}
@tab Charter
@item @code{ccr}
@tab Computer Concrete
@item @code{cmr}
@tab Computer Modern
@item @code{cmss}
@tab Computer Modern Sans Serif
@item @code{cmtt}
@tab Computer Modern Typewriter
@item @code{pcr}
@tab Courier
@item @code{phv}
@tab Helvetica
@item @code{fi4}
@tab Inconsolata
@item @code{lmr}
@tab Latin Modern
@item @code{lmss}
@tab Latin Modern Sans
@item @code{lmtt}
@tab Latin Modern Typewriter
@item @code{pnc}
@tab New Century Schoolbook
@item @code{ppl}
@tab Palatino
@item @code{ptm}
@tab Times
@item @code{uncl}
@tab Uncial
@item @code{put}
@tab Utopia
@item @code{pzc}
@tab Zapf Chancery
@end multitable


@anchor{low level font commands fontseries}
@item \fontseries@{@var{series}@}
@findex \fontseries
@cindex series, of fonts
Select the font series.  A @dfn{series} combines a @dfn{weight} and a
@dfn{width}.  Typically, a font supports only a few of the possible
combinations.  Some common combined series values include:

@multitable {xx} {Medium (normal)xx}
@item @code{m}
@tab Medium (normal)
@item @code{b}
@tab Bold
@item @code{c}
@tab Condensed
@item @code{bc}
@tab Bold condensed
@item @code{bx}
@tab Bold extended
@end multitable

@cindex weights, of fonts
The possible values for weight, individually, are:

@multitable {xx} {Medium (normal) xx}
@item @code{ul}
@tab Ultra light
@item @code{el}
@tab Extra light
@item @code{l}
@tab Light
@item @code{sl}
@tab Semi light
@item @code{m}
@tab Medium (normal)
@item @code{sb}
@tab Semi bold
@item @code{b}
@tab Bold
@item @code{eb}
@tab Extra bold
@item @code{ub}
@tab Ultra bold
@end multitable
 
@cindex widths, of fonts
The possible values for width, individually, are (the meaning and
relationship of these terms varies with individual typefaces):

@multitable {xx} {Ultra condensed}
@item @code{uc}
@tab Ultra condensed
@item @code{ec}
@tab Extra condensed
@item @code{c}
@tab Condensed
@item @code{sc}
@tab Semi condensed
@item @code{m}
@tab Medium
@item @code{sx}
@tab Semi expanded
@item @code{x}
@tab Expanded
@item @code{ex}
@tab Extra expanded
@item @code{ux}
@tab Ultra expanded
@end multitable

When forming the @var{series} string from the weight and width, drop the
@code{m} that stands for medium weight or medium width, unless both
weight and width are @code{m}, in which case use just one
(@samp{@code{m}}).
 
@item \fontshape@{@var{shape}@}
@findex \fontshape
@cindex shapes, of fonts
@anchor{low level font commands fontshape}
Select font shape. Valid shapes are:

@multitable {xx} {Slanted (oblique)xx}
@item @code{n}
@tab Upright (normal)
@item @code{it}
@tab Italic
@item @code{sl}
@tab Slanted (oblique)
@item @code{sc}
@tab Small caps
@item @code{ui}
@tab Upright italics
@item @code{ol}
@tab Outline
@end multitable

The two last shapes are not available for most font families, and
small caps are often missing as well.

@anchor{low level font commands fontsize}
@item \fontsize@{@var{size}@}@{@var{skip}@}
@findex \fontsize
@cindex font size
@findex \baselineskip
Set the font size and the line spacing.  The unit of both parameters
defaults to points (@code{pt}).  The line spacing is the nominal
vertical space between lines, baseline to baseline.  It is stored in the
parameter @code{\baselineskip}.  The default @code{\baselineskip} for
the Computer Modern typeface is 1.2 times the @code{\fontsize}.
Changing @code{\baselineskip} directly is inadvisable since its value is
reset every time a size change happens; see @code{\baselinestretch}, next.

@anchor{low level font commands baselinestretch}
@item \baselinestretch
@findex \baselinestretch
@LaTeX{} multiplies the line spacing by the value of the
@code{\baselinestretch} parameter; the default factor is 1.  A change
takes effect when @code{\selectfont} (see below) is called.  You can
make a line skip change happen for the entire document, for instance
doubling it, by doing @code{\renewcommand@{\baselinestretch@}@{2.0@}} in
the preamble.

@PkgIndex{setspace}
@cindex double spacing
However, the best way to double-space a document is to use the
@file{setspace} package.  In addition to offering a number of spacing
options, this package keeps the line spacing single-spaced in places
where that is typically desirable, such as footnotes and figure
captions.  See the package documentation.

@anchor{low level font commands linespread}
@item \linespread@{@var{factor}@}
@findex \linespread
Equivalent to
@code{\renewcommand@{\baselinestretch@}@{@var{factor}@}}, and
therefore must be followed by @code{\selectfont} to have any effect.
Best specified in the preamble, or use the @code{setspace} package, as
just described.

@anchor{low level font commands selectfont}
@item \selectfont
@findex \selectfont
The effects of the font commands described above do not happen until
@code{\selectfont} is called, as in
@code{\fontfamily@{@var{familyname}@}\selectfont}.  It is often useful
to put this in a macro:@*
@code{\newcommand*@{\myfont@}@{\fontfamily@{@var{familyname}@}\selectfont@}}@*
(@pxref{\newcommand & \renewcommand}).

@anchor{low level font commands usefont}
@item \usefont@{@var{enc}@}@{@var{family}@}@{@var{series}@}@{@var{shape}@}
@findex \usefont
The same as invoking @code{\fontencoding}, @code{\fontfamily},
@code{\fontseries} and @code{\fontshape} with the given parameters,
followed by @code{\selectfont}.  For example:

@example
\usefont@{ot1@}@{cmr@}@{m@}@{n@}
@end example

@end table


@node Layout
@chapter Layout

@cindex layout commands

Commands for controlling the general page layout.

@menu
* \onecolumn::              Use one-column layout.
* \twocolumn::              Use two-column layout.
* \flushbottom::            Make all text pages the same height.
* \raggedbottom::           Allow text pages of differing height.
* Page layout parameters::  @code{\headheight} @code{\footskip}.
* Floats::                  Figures, tables, etc.
@end menu


@node \onecolumn
@section @code{\onecolumn}

@findex \onecolumn
@cindex one-column output

Synopsis:

@example
\onecolumn
@end example

Start a new page and produce single-column output.  If the document is
given the class option @code{onecolumn} then this is the default
behavior (@pxref{Document class options}).  This command is fragile
(@pxref{\protect}).


@node \twocolumn
@section @code{\twocolumn}

@findex \twocolumn
@cindex multicolumn text
@cindex two-column output

Synopses:

@example
\twocolumn
\twocolumn[@var{prelim one column text}]
@end example

Start a new page and produce two-column output. If the document is given
the class option @code{twocolumn} then this is the default
(@pxref{Document class options}).  This command is fragile
(@pxref{\protect}).

If the optional @var{prelim one column text} argument
is present, it is typeset in one-column mode before the two-column
typesetting starts.

These parameters control typesetting in two-column output:

@ftable @code
@item \columnsep
@anchor{twocolumn columnsep}
The distance between columns. The default is 35pt.  Change it with a
command such as @code{\setlength@{\columnsep@}@{40pt@}} You must change
it before the two column environment starts; in the preamble is a good
place.

@item \columnseprule
@anchor{twocolumn columnseprule}
The width of the rule between columns. The rule appears halfway between
the two columns.  The default is 0pt, meaning that there is no rule.
Change it with a command such as
@code{\setlength@{\columnseprule@}@{0.4pt@}}, before the two-column
environment starts.

@item \columnwidth
@anchor{twocolumn columnwidth}
The width of a single column.  In one-column mode this is equal to
@code{\textwidth}.  In two-column mode by default @LaTeX{} sets the
width of each of the two columns to be half of @code{\textwidth} minus
@code{\columnsep}.

@end ftable

In a two-column document, the starred environments @code{table*} and
@code{figure*} are two columns wide, whereas the unstarred environments
@code{table} and @code{figure} take up only one column (@pxref{figure}
and @pxref{table}). @LaTeX{} places starred floats at the top of a page.
The following parameters control float behavior of two-column output.

@ftable @code
@anchor{twocolumn dbltopfraction}
@item \dbltopfraction
The maximum fraction at the top of a two-column page that may be
occupied by two-column wide floats.  The default is 0.7, meaning that
the height of a @code{table*} or @code{figure*} environment must not
exceed @code{0.7\textheight} .  If the height of your starred float
environment exceeds this then you can take one of the following actions
to prevent it from floating all the way to the back of the document:

@itemize @bullet
@item
Use the @code{[tp]} location specifier to tell LaTeX to try to put
the bulky float on a page by itself, as well as at the top of a page.

@item
Use the @code{[t!]} location specifier to override the effect of
@code{\dbltopfraction} for this particular float.

@item
Increase the value of @code{\dbltopfraction} to a suitably large number,
to avoid going to float pages so soon.
@end itemize

You can redefine it, as with
@code{\renewcommand@{\dbltopfraction@}@{0.9@}}.

@anchor{twocolumn dblfloatpagefraction}
@item \dblfloatpagefraction
For a float page of two-column wide floats, this is the minimum fraction
that must be occupied by floats, limiting the amount of blank space.
@LaTeX{}'s default is @code{0.5}.  Change it with @code{\renewcommand}.

@anchor{twocolumn dblfloatsep}
@item \dblfloatsep
On a float page of two-column wide floats, this length is the distance
between floats, at both the top and bottom of the page.  The default is
@code{12pt plus2pt minus2pt} for a document set at @code{10pt} or
@code{11pt}, and @code{14pt plus2pt minus4pt} for a document set at
@code{12pt}.

@anchor{twocolumn dbltextfloatsep}
@item \dbltextfloatsep
This length is the distance between a multi-column float at the top or
bottom of a page and the main text.  The default is @code{20pt plus2pt
minus4pt}.

@anchor{twocolumn dbltopnumber}
@item \dbltopnumber
On a float page of two-column wide floats, this counter gives the
maximum number of floats allowed at the top of the page.  The @LaTeX{}
default is @code{2}.

@end ftable

@c From egreg at http://tex.stackexchange.com/a/142232/339
This example uses @code{\twocolumn}'s optional argument of to create a
title that spans the two-column article:

@example
\documentclass[twocolumn]@{article@}
\newcommand@{\authormark@}[1]@{\textsuperscript@{#1@}@}
\begin@{document@}
\twocolumn[@{% inside this optional argument goes one-column text
  \centering
  \LARGE The Title \\[1.5em]
  \large Author One\authormark@{1@},
         Author Two\authormark@{2@},
         Author Three\authormark@{1@} \\[1em]
  \normalsize
  \begin@{tabular@}@{p@{.2\textwidth@}@@@{\hspace@{2em@}@}p@{.2\textwidth@}@}
    \authormark@{1@}Department one  &\authormark@{2@}Department two \\ 
     School one                   &School two 
  \end@{tabular@}\\[3em] % space below title part
  @}]

Two column text here.
@end example


@node \flushbottom
@section @code{\flushbottom}

@findex \flushbottom

Make all pages in the documents after this declaration have the same
height, by stretching the vertical space where necessary to fill out the
page.  This is most often used when making two-sided documents since the
differences in facing pages can be glaring.

If @TeX{} cannot satisfactorily stretch the vertical space in a page
then you get a message like @samp{Underfull \vbox (badness 10000) has
occurred while \output is active}.  If you get that, one option is to
change to @code{\raggedbottom} (@pxref{\raggedbottom}).  Alternatively,
you can adjust the @code{textheight} to make compatible pages, or you
can add some vertical stretch glue between lines or between paragraphs,
as in @code{\setlength@{\parskip@}@{0ex plus0.1ex@}}.  Your last option
is to, in a final editing stage, adjust the height of individual pages
(@pxref{\enlargethispage}).

The @code{\flushbottom} state is the default only if you select the
@code{twoside} document class option (@pxref{Document class options}).


@node \raggedbottom
@section @code{\raggedbottom}

@findex \raggedbottom
@cindex stretch, omitting vertical

Make all later pages the natural height of the material on that page; no
rubber vertical lengths will be stretched.  Thus, in a two-sided
document the facing pages may be different heights.  This command can go
at any point in the document body.  See @ref{\flushbottom}.

This is the default unless you select the @code{twoside} document class
option (@pxref{Document class options}).


@node Page layout parameters
@section Page layout parameters

@cindex page layout parameters
@cindex parameters, page layout
@cindex layout, page parameters for
@cindex header, parameters for
@cindex footer, parameters for
@cindex running header and footer

@ftable @code
@item \columnsep
@itemx \columnseprule
@itemx \columnwidth
@findex \columnsep
@findex \columnseprule
@findex \columnwidth
@anchor{page layout parameters columnsep}
@anchor{page layout parameters columnseprule}
@anchor{page layout parameters columnwidth}
The distance between the two columns, the width of a rule between the
columns, and the width of the columns, when the document class option
@code{twocolumn} is in effect (@pxref{Document class options}).
@xref{\twocolumn}.

@item \headheight
@findex \headheight
@anchor{page layout parameters headheight}
Height of the box that contains the running head.  The default in the
@code{article}, @code{report}, and @code{book} classes is @samp{12pt},
at all type sizes.

@item \headsep
@findex \headsep 
@anchor{page layout parameters headsep}
Vertical distance between the bottom of the header line and the top of
the main text.  The default in the @code{article} and @code{report}
classes is @samp{25pt}.  In the @code{book} class the default is: if the
document is set at 10pt then it is @samp{0.25in}, and at 11pt and 12pt
it is @samp{0.275in}.

@item \footskip
@findex \footskip
@anchor{page layout parameters footskip}
Distance from the baseline of the last line of text to the baseline of
the page footer.  The default in the @code{article} and @code{report}
classes is @samp{30pt}.  In the @code{book} class the default is: when
the type size is 10pt the default is @samp{0.35in}, while at 11pt it is
@samp{0.38in}, and at 12pt it is @samp{30pt}.

@item \linewidth
@findex \linewidth
@anchor{page layout parameters linewidth}
Width of the current line, decreased for each nested @code{list}
(@pxref{list}).  That is, the nominal value for @code{\linewidth} is to
equal @code{\textwidth} but for each nested list the @code{\linewidth}
is decreased by the sum of that list's @code{\leftmargin} and
@code{\rightmargin} (@pxref{itemize}).
@c The default varies with the font size, paper width, two-column mode,
@c etc.  For an @code{article} document set in 10pt, the default is
@c @samp{345pt}, while in two-column mode that becomes @samp{229.5pt}.

@item \marginparpush
@itemx \marginsep
@itemx \marginparwidth
@findex \marginparpush
@findex \marginsep
@findex \marginparwidth
@anchor{page layout parameters marginparpush}
@anchor{page layout parameters marginsep}
@anchor{page layout parameters marginparwidth}
The minimum vertical space between two marginal notes, the horizontal
space between the text body and the marginal notes, and the horizontal
width of the notes.

Normally marginal notes appear on the outside of the page, but the
declaration @code{\reversemarginpar} changes that (and
@code{\normalmarginpar} changes it back).

The defaults for @code{\marginparpush} in both @code{book} and
@code{article} classes are: @samp{7pt} if the document is set at 12pt,
and @samp{5pt} if the document is set at 11pt or 10pt.

For @code{\marginsep}, in @code{article} class the default is
@samp{10pt} except if the document is set at 10pt and in two-column mode
where the default is @samp{11pt}.

For @code{\marginsep} in @code{book} class the default is @samp{10pt} in
two-column mode and @samp{7pt} in one-column mode.  

For @code{\marginparwidth} in both @code{book} and @code{article}
classes, in two-column mode the default is 60% of @code{\paperwidth
@minus{} \textwidth}, while in one-column mode it is 50% of that
distance.

@item \oddsidemargin
@itemx \evensidemargin
@findex \oddsidemargin
@findex \evensidemargin
@anchor{page layout parameters oddsidemargin}
@anchor{page layout parameters evensidemargin}
The @code{\oddsidemargin} is the extra distance between the left side of
the page and the text's left margin, on odd-numbered pages when the
document class option @code{twoside} is chosen and on all pages when
@code{oneside} is in effect.  When @code{twoside} is in effect, on
even-numbered pages the extra distance on the left is
@code{evensidemargin}.

@LaTeX{}'s default is that @code{\oddsidemargin} is 40% of the
difference between @code{\paperwidth} and @code{\textwidth}, and
@code{\evensidemargin} is the remainder.

@item \paperheight
@findex \paperheight
@anchor{page layout parameters paperheight}
The height of the paper, as distinct from the height of the print area.
Normally set with a document class option, as in
@code{\documentclass[a4paper]@{article@}} (@pxref{Document class
options}).

@item \paperwidth
@findex \paperwidth
@anchor{page layout parameters paperwidth}
The width of the paper, as distinct from the width of the print area.
Normally set with a document class option, as in
@code{\documentclass[a4paper]@{article@}} (@pxref{Document class
options}).

@item \textheight
@findex \textheight
@anchor{page layout parameters textheight}
The normal vertical height of the page body.  If the document is set at
a nominal type size of 10pt then for an @code{article} or @code{report}
the default is @samp{43\baselineskip}, while for a @code{book} it is
@samp{41\baselineskip}.  At a type size of 11pt the default is
@samp{38\baselineskip} for all document classes.  At 12pt it is
@samp{36\baselineskip} for all classes.

@item \textwidth
@findex \textwidth
@anchor{page layout parameters textwidth}
The full horizontal width of the entire page body.  For an
@code{article} or @code{report} document, the default is @samp{345pt}
when the chosen type size is 10pt, the default is @samp{360pt} at 11pt,
and it is @samp{390pt} at 12pt.  For a @code{book} document, the default
is @samp{4.5in} at a type size of 10pt, and @samp{5in} at 11pt or 12pt.

In multi-column output, @code{\textwidth} remains the width of the
entire page body, while @code{\columnwidth} is the width of one column
(@pxref{\twocolumn}).

In lists (@pxref{list}), @code{\textwidth} remains the width of the
entire page body (and @code{\columnwidth} the width of the entire
column), while @code{\linewidth} may decrease for nested lists.

Inside a minipage (@pxref{minipage}) or @code{\parbox}
(@pxref{\parbox}), all the width-related parameters are set to the
specified width, and revert to their normal values at the end of the
@code{minipage} or @code{\parbox}.

@findex \hsize
@anchor{page layout parameters hsize}
@item \hsize
This entry is included for completeness: @code{\hsize} is the @TeX{}
primitive parameter used when text is broken into lines.  It should not
be used in normal @LaTeX{} documents.

@item \topmargin
@findex topmargin
@anchor{page layout parameters topmargin}
Space between the top of the @TeX{} page (one inch from the top of the
paper, by default) and the top of the header.  The value is computed
based on many other parameters: @code{\paperheight @minus{} 2in @minus{}
\headheight @minus{} \headsep @minus{} \textheight @minus{} \footskip},
and then divided by two.

@item \topskip
@findex \topskip
@anchor{page layout parameters topskip}
Minimum distance between the top of the page body and the baseline of
the first line of text.  For the standard classes, the default is the
same as the font size, e.g., @samp{10pt} at a type size of 10pt.

@end ftable


@node Floats
@section Floats

Some typographic elements, such as figures and tables, cannot be broken
across pages.  They must be typeset outside of the normal flow of text,
for instance floating to the top of a later page.

@LaTeX{} can have a number of different classes of floating material.
The default is the two classes, @code{figure} (@pxref{figure}) and
@code{table} (@pxref{table}), but you can create a new class with the
package @file{float}.

Within any one float class @LaTeX{} always respects the order, so that
the first figure in a document source must be typeset before the second
figure.  However, @LaTeX{} may mix the classes, so it can happen that
while the first table appears in the source before the first figure, it
appears in the output after it.

The placement of floats is subject to parameters, given below, that
limit the number of floats that can appear at the top of a page, and
the bottom, etc. If so many floats are queued that the limits prevent
them all from fitting on a page then @LaTeX{} places what it can and
defers the rest to the next page.  In this way, floats may end up
being typeset far from their place in the source.  In particular, a
float that is big may migrate to the end of the document. In which
event, because all floats in a class must appear in sequential order,
every following float in that class also appears at the end.

@cindex placement of floats
@cindex specifier, float placement
In addition to changing the parameters, for each float you can tweak
where the float placement algorithm tries to place it by using its
@var{placement} argument.  The possible values are a sequence of the
letters below. The default for both @code{figure} and @code{table}, in
both @code{article} and @code{book} classes, is @code{tbp}.

@table @code
@item t
(Top)---at the top of a text page.

@item b
(Bottom)---at the bottom of a text page.  (However, @code{b} is not
allowed for full-width floats (@code{figure*}) with double-column
output.  To ameliorate this, use the @file{stfloats} or
@file{dblfloatfix} package, but see the discussion at caveats in the
FAQ: @url{http://www.tex.ac.uk/cgi-bin/texfaq2html?label=2colfloat}.

@item h
(Here)---at the position in the text where the @code{figure} environment
appears.  However, @code{h} is not allowed by itself; @code{t} is
automatically added.

@cindex here, putting floats
@PkgIndex{float}
To absolutely force a float to appear ``here'', you can
@code{\usepackage@{float@}} and use the @code{H} specifier which it
defines.  For further discussion, see the FAQ entry at
@url{http://www.tex.ac.uk/cgi-bin/texfaq2html?label=figurehere}.

@item p
@cindex float page
(Page of floats)---on a separate @dfn{float page}, which is a page
containing no text, only floats.

@item !
Used in addition to one of the above; for this float only, @LaTeX{}
ignores the restrictions on both the number of floats that can appear
and the relative amounts of float and non-float text on the page.
The @code{!} specifier does @emph{not} mean ``put the float here'';
see above.

@end table

Note: the order in which letters appear in the @var{placement} argument
does not change the order in which @LaTeX{} tries to place the float;
for instance, @code{btp} has the same effect as @code{tbp}.  All that
@var{placement} does is that if a letter is not present then the
algorithm does not try that location.  Thus, @LaTeX{}'s default of
@code{tbp} is to try every location except placing the float where it
occurs in the source.

To prevent @LaTeX{} from moving floats to the end of the document or a
chapter you can use a @code{\clearpage} command to start a new page and
insert all pending floats. If a pagebreak is undesirable then you can
use the @file{afterpage} package and issue
@code{\afterpage@{\clearpage@}}.  This will wait until the current page
is finished and then flush all outstanding floats.

@PkgIndex{flafter}
@LaTeX{} can typeset a float before where it appears in the source
(although on the same output page) if there is a @code{t} specifier in
the @var{placement} parameter.  If this is not desired, and deleting
the @code{t} is not acceptable as it keeps the float from being placed
at the top of the next page, then you can prevent it by either using
the @file{flafter} package or using the command
@findex \suppressfloats 
@code{\suppressfloats[t]}, which causes floats for the top position on
this page to moved to the next page.

Parameters relating to fractions of pages occupied by float and
non-float text (change them with
@code{\renewcommand@{@var{parameter}@}@{@var{decimal between 0 and 1}@}}):

@ftable @code
@item \bottomfraction
@findex \bottomfraction
@anchor{floats bottomfraction}
The maximum fraction of the page allowed to be occupied by floats at
the bottom; default @samp{.3}.

@item \floatpagefraction
@findex \floatpagefraction
@anchor{floats floatpagefraction}
The minimum fraction of a float page that must be occupied by floats;
default @samp{.5}.

@item \textfraction
@findex \textfraction
@anchor{floats textfraction}
Minimum fraction of a page that must be text; if floats take up too
much space to preserve this much text, floats will be moved to a
different page.  The default is @samp{.2}.

@item \topfraction
@findex \topfraction
@anchor{floats topfraction}
Maximum fraction at the top of a page that may be occupied before
floats; default @samp{.7}.
@end ftable

Parameters relating to vertical space around floats (change them with a
command of the form @code{\setlength@{@var{parameter}@}@{@var{length
expression}@}}):

@ftable @code
@item \floatsep
@findex \floatsep
@anchor{floats floatsep}
Space between floats at the top or bottom of a page; default
@samp{12pt plus2pt minus2pt}.

@item \intextsep
@findex \intextsep
@anchor{floats intextsep}
Space above and below a float in the middle of the main text; default
@samp{12pt plus2pt minus2pt} for 10 point and 11 point documents,
and @samp{14pt plus4pt minus4pt} for 12 point documents.

@item \textfloatsep
@findex \textfloatsep
@anchor{floats textfloatsep}
Space between the last (first) float at the top (bottom) of a page;
default @samp{20pt plus2pt minus4pt}.
@end ftable

Counters relating to the number of floats on a page (change them with a
command of the form @code{\setcounter@{@var{ctrname}@}@{@var{natural
number}@}}):

@ftable @code
@item bottomnumber
@findex bottomnumber
@anchor{floats bottomnumber}
Maximum number of floats that can appear at the bottom of a text page;
default 1.

@item dbltopnumber
@findex dbltopnumber
@anchor{floats dbltopnumber}
Maximum number of full-sized floats that can appear at the top of a
two-column page; default 2.

@item topnumber
@findex topnumber
@anchor{floats topnumber}
Maximum number of floats that can appear at the top of a text page;
default 2.

@item totalnumber
@findex totalnumber
@anchor{floats totalnumber}
Maximum number of floats that can appear on a text page; default 3.
@end ftable

The principal @TeX{}@tie{}FAQ entry relating to floats
@url{http://www.tex.ac.uk/cgi-bin/texfaq2html?label=floats} contains
suggestions for relaxing @LaTeX{}'s default parameters to reduce the
problem of floats being pushed to the end.  A full explanation of the
float placement algorithm is in Frank Mittelbach's article ``How to
influence the position of float environments like figure and table in
@LaTeX{}?''
(@url{http://latex-project.org/papers/tb111mitt-float.pdf}).


@node Sectioning
@chapter Sectioning

@cindex sectioning commands
@cindex part
@cindex chapter
@cindex section
@cindex subsection
@cindex paragraph
@cindex subparagraph
@findex \part
@findex \chapter
@findex \section
@findex \subsection
@findex \paragraph
@findex \subparagraph

Structure your text into divisions: parts, chapters, sections, etc.  All
sectioning commands have the same form, one of:

@example
@var{sectioning-command}@{@var{title}@}
@var{sectioning-command}*@{@var{title}@}
@var{sectioning-command}[@var{toc-title}]@{@var{title}@}
@end example

@noindent
For instance, declare the start of a subsection as with
@code{\subsection@{Motivation@}}.

The table has each @var{sectioning-command} in @LaTeX{}.  All are
available in all of @LaTeX{}'s standard document classes @code{book},
@code{report}, and@tie{}@code{article}, except that @code{\chapter} is
not available in @code{article}.

@multitable @columnfractions .25 .25 .40 
@headitem Sectioning unit  @tab Command  @tab Level 
@item Part
@tab @code{\part}  @tab -1 (@code{book}, @code{report}), 0 (@code{article})
@item Chapter
@tab @code{\chapter}   @tab 0
@item Section
@tab @code{\section}   @tab 1 
@item Subsection
@tab @code{\subsection}   @tab 2 
@item Subsubsection
@tab @code{\subsubsection}   @tab 3  
@item Paragraph
@tab @code{\paragraph}   @tab 4  
@item Subparagraph
@tab @code{\subparagraph}   @tab 5  
@end multitable

@cindex @code{*}-form of sectioning commands
All these commands have a @code{*}-form that prints @var{title} as usual
but is not numbered and does not make an entry in the table of contents.
An example of using this is for an appendix in an @code{article} .  The
input @code{\appendix\section@{Appendix@}} gives the output @samp{A
Appendix} (@pxref{\appendix}).  You can lose the numbering@tie{}@samp{A}
by instead entering @code{\section*@{Appendix@}} (articles often omit a
table of contents and have simple page headers so the other differences
from the @code{\section} command may not matter).

The section title @var{title} provides the heading in the main text, but
it may also appear in the table of contents and in the running head or
foot (@pxref{Page styles}).  You may not want the same text in these
places as in the main text.  All of these commands have an optional
argument @var{toc-title} for these other places.

The level number in the table above determines which sectional units are
numbered, and which appear in the table of contents.  If the sectioning
command's @var{level} is less than or equal to the value of the counter
@code{secnumdepth} then the titles for this sectioning command will be
numbered (@pxref{Sectioning/secnumdepth}).  And, if @var{level} is less
than or equal to the value of the counter @code{tocdepth} then the table
of contents will have an entry for this sectioning unit
(@pxref{Sectioning/tocdepth}).

@LaTeX{} expects that before you have a @code{\subsection} you will have
a @code{\section} and, in a book, that before a @code{\section} you will
have a @code{\chapter}.  Otherwise you can get a something like a
subsection numbered @samp{3.0.1}.

Two counters relate to the appearance of sectioning commands.

@ftable @code
@item secnumdepth
@findex secnumdepth @r{counter}
@cindex section numbers, printing
@anchor{sectioning secnumdepth}
@anchor{Sectioning/secnumdepth}
Controls which sectioning commands are
numbered.  Suppress numbering of sectioning at any depth greater than
@var{level} @code{\setcounter@{secnumdepth@}@{@var{level}@}}
(@pxref{\setcounter}).  See the above table for the level numbers.  For
instance, if the @code{secnumdepth} is 1 in an @code{article} then a
@code{\section@{Introduction@}} command will produce output like @samp{1
Introduction} while @code{\subsection@{Discussion@}} will produce output
like @samp{Discussion}, without the number. @LaTeX{}'s default
@code{secnumdepth} is@tie{}3 in @file{article} class and @tie{}2 in the
@file{book} and @file{report} classes.

@item tocdepth
@findex tocdepth @r{counter}
@cindex table of contents, sectioning numbers printed
@anchor{sectioning tocdepth}
@anchor{Sectioning/tocdepth}
Controls which sectioning units are listed in the table of contents.
The setting @code{\setcounter@{tocdepth@}@{@var{level}@}} makes the
sectioning units at @var{level} be the smallest ones listed
(@pxref{\setcounter}).  See the above table for the level numbers.  For
instance, if @code{tocdepth} is@tie{}1 then the table of contents will
list sections but not subsections.  @LaTeX{}'s default
@code{secnumdepth} is@tie{}3 in @file{article} class and @tie{}2 in the
@file{book} and @file{report} classes.

@end ftable

@menu
* \part::                                         Start a part.
* \chapter::                                      Start a chapter.
* \section::                                      Start a section.
* \subsection::                                   Start a subsection.
* \subsubsection & \paragraph & \subparagraph::   Lower divisions.
* \appendix::                                     Start appendices.
* \frontmatter & \mainmatter & \backmatter::      The three parts of a book.
* \@@startsection::                               Layout of sectional units.
@end menu


@node \part
@section @code{\part}

@findex \part
@cindex part
@cindex sectioning, part

Synopsis, one of:

@example
\part@{@var{title}@}
\part*@{@var{title}@}
\part[@var{toc-title}]@{@var{title}@}
@end example

Start a document part.  The standard @LaTeX{} classes @code{book},
@code{report}, and @code{article}, all have this command.

This produces a document part, in a book.

@example
\part@{VOLUME I \\
       PERSONAL MEMOIRS OF  U.\ S.\ GRANT@}
\chapter@{ANCESTRY--BIRTH--BOYHOOD.@}
My family is American, and has been for generations,
in all its branches, direct and collateral.
@end example

In each standard class the @code{\part} command outputs a part number
such as @samp{Part I}, alone on its line, in boldface, and in large
type.  Then @LaTeX{} outputs @var{title}, also alone on its line, in
bold and in even larger type.  In class @code{book}, the @LaTeX{}
default puts each part alone on its own page. If the book is two-sided
then @LaTeX{} will skip a page if needed to have the new part on an
odd-numbered page.  In @code{report} it is again alone on a page, but
@LaTeX{} won't force it onto an odd-numbered page.  In an @code{article}
@LaTeX{} does not put it on a fresh page, but instead outputs the part
number and part title onto the main document page.

The @code{*}@tie{}form shows @var{title} 
but it does not show the part number, does not increment the
@code{part} counter, and produces no table of contents entry.

The optional argument @var{toc-title} will appear as the part title in
the table of contents (@pxref{Table of contents etc.}) and in running
headers (@pxref{Page styles}).  If it is not present then @var{title}
will be there.  This example puts a line break in @var{title} but leaves
out the break in the table of contents.

@example
\part[Up from the bottom; my life]@{Up from the bottom\\ my life@}
@end example

For determining which sectional units are numbered and which appear in
the table of contents, the level number of a part is@tie{}-1
(@pxref{Sectioning/secnumdepth} and @pxref{Sectioning/tocdepth}).

@PkgIndex{indentfirst}
In the class @code{article}, if a paragraph immediately follows the part
title then it is not indented.  To get an indent you can use the package
@file{indentfirst}.

@PkgIndex{titlesec}
One package to change the behavior of @code{\part} is @file{titlesec}.
See its documentation on CTAN.


@node \chapter
@section @code{\chapter}

@findex \chapter
@cindex chapter

Synopsis, one of:

@example
\chapter@{@var{title}@}
\chapter*@{@var{title}@}
\chapter[@var{toc-title}]@{@var{title}@}
@end example

Start a chapter.  The standard @LaTeX{} classes @code{book} and
@code{report} have this command but @code{article} does not.

This produces a chapter.

@example
\chapter@{Loomings@}
Call me Ishmael.
Some years ago---never mind how long precisely---having little or no
money in my purse, and nothing particular to interest me on shore, I
thought I would sail about a little and see the watery part of
the world.
@end example

The @LaTeX{} default starts each chapter on a fresh page, an
odd-numbered page if the document is two-sided.  It produces a chapter
number such as @samp{Chapter 1} in large boldface type (the size is
@code{\huge}).  It then puts @var{title} on a fresh line, in boldface
type that is still larger (size @code{\Huge}).  It also increments the
@code{chapter} counter, adds an entry to the table of contents
(@pxref{Table of contents etc.}), and sets the running header
information (@pxref{Page styles}).

The @code{*}@tie{}form shows @var{title} on a fresh line, in boldface.
But it does not show the chapter number, does not increment the
@code{chapter} counter, produces no table of contents entry, and does
not affect the running header.  (If you use the page style
@code{headings} in a two-sided document then the header will be from the
prior chapter.)  This example illustrates.

@example
\chapter*@{Preamble@}
@end example

The optional argument @var{toc-title} will appear as the chapter title
in the table of contents (@pxref{Table of contents etc.}) and in
running headers (@pxref{Page styles}).  If it is not present then
@var{title} will be there.  This shows the full name in the chapter
title,

@example
\chapter[Weyl]@{Hermann Klaus Hugo (Peter) Weyl (1885--1955)@}
@end example

@noindent
but only @samp{Weyl} on the contents page.  This puts a line break in
the title but that doesn't work well with running headers so it omits
the break in the contents

@example
\chapter[Given it all\\ my story]@{Given it all\\ my story@}
@end example

For determining which sectional units are numbered and which appear in
the table of contents, the level number of a chapter is@tie{}0
(@pxref{Sectioning/secnumdepth} and @pxref{Sectioning/tocdepth}).

@PkgIndex{indentfirst}
The paragraph that follows the chapter title is not indented, as is a
standard typographical practice.  To get an indent use the package
@file{indentfirst}.

You can change what is shown for the chapter number.  To change it to
something like @samp{Lecture 1}, put in the preamble either
@code{\renewcommand@{\chaptername@}@{Lecture@}} or this
(@pxref{\makeatletter & \makeatother}).

@example
\makeatletter
\renewcommand@{\@@chapapp@}@{Lecture@}
\makeatother
@end example

@PkgIndex{babel}
@noindent To make this change because of the primary language for
the document, see the package @file{babel}.

In a two-sided document @LaTeX{} puts a chapter on odd-numbered page, if
necessary leaving an even-numbered page that is blank except for any
running headers.  To make that page completely blank,
see@tie{}@ref{\clearpage & \cleardoublepage}.

@PkgIndex{titlesec}
To change the behavior of the @code{\chapter} command, you can copy its
definition from the @LaTeX{} format file and make adjustments.  But
there are also many packages on CTAN that address this.  One is
@file{titlesec}.  See its documentation, but the example below gives a
sense of what it can do.

@example
\usepackage@{titlesec@}   % in preamble
\titleformat@{\chapter@}
  @{\Huge\bfseries@}  % format of title
  @{@}                % label, such as 1.2 for a subsection
  @{0pt@}             % length of separation between label and title
  @{@}                % before-code hook
@end example

@noindent
This omits the chapter number @samp{Chapter 1} from the page but unlike
@code{\chapter*} it keeps the chapter in the table of contents and the
running headers.


@node \section
@section @code{\section}

@findex \section
@cindex section

Synopsis, one of:

@example
\section@{@var{title}@}
\section*@{@var{title}@}
\section[@var{toc-title}]@{@var{title}@}
@end example

Start a section.  The standard @LaTeX{} classes @code{article},
@code{book}, and @code{report} all have this command.

This produces a section.

@example
In this Part we tend to be more interested in the function,
in the input-output behavior,
than in the details of implementing that behavior.

\section@{Turing machines@}
Despite this desire to downplay implementation,
we follow the approach of A~Turing that the
first step toward defining the set of computable functions
is to reflect on the details of what mechanisms can do.
@end example

For the standard @LaTeX{} classes @code{book} and @code{report} the
default output is like @samp{1.2 @var{title}} (for chapter@tie{}1,
section@tie{}2), alone on its line and flush left, in boldface and a
larger type (the type size is @code{\Large}).  The same holds in
@code{article} except that there are no chapters in that class so it
looks like @samp{2 @var{title}}.

The @code{*}@tie{}form shows @var{title}.
But it does not show the section number, does not increment the
@code{section} counter, produces no table of contents entry, and does
not affect the running header.  (If you use the page style
@code{headings} in a two-sided document then the header will be from the
prior section.)

The optional argument @var{toc-title} will appear as the section title
in the table of contents (@pxref{Table of contents etc.}) and in
running headers (@pxref{Page styles}).  If it is not present then
@var{title} will be there.  This shows the full name in the title of the
section,

@example
\section[Elizabeth~II]@{Elizabeth the Second,
  by the Grace of God of the United Kingdom,
  Canada and Her other Realms and Territories Queen,
  Head of the Commonwealth, Defender of the Faith.@}
@end example

@noindent
but only @samp{Elizabeth II} on the contents page and in the headers.
This has a line break in @var{title} but that does not work with headers
so it is omitted from the contents and headers.

@example
\section[Truth is, I cheated; my life story]@{Truth is,
  I cheated\\my life story@}
@end example

For determining which sectional units are numbered and which appear in
the table of contents, the level number of a section is@tie{}1
(@pxref{Sectioning/secnumdepth} and @pxref{Sectioning/tocdepth}).

@PkgIndex{indentfirst}
The paragraph that follows the section title is not indented, as is a
standard typographical practice.  One way to get an indent is to use the
package @file{indentfirst}.

@PkgIndex{titlesec}
In general, to change the behavior of the @code{\section} command, there
are a number of options.  One is the @code{\@@startsection} command
(@pxref{\@@startsection}).  There are also many packages on CTAN that
address this, including @file{titlesec}.  See the documentation but the
example below gives a sense of what they can do.

@c credit: egreg https://groups.google.com/forum/#!topic/comp.text.tex/tvc8oM5P4y4
@example
\usepackage@{titlesec@}   % in preamble
\titleformat@{\section@}
  @{\normalfont\Large\bfseries@}  % format of title
  @{\makebox[1pc][r]@{\thesection\hspace@{1pc@}@}@} % label
  @{0pt@}                   % length of separation between label and title
  @{@}                      % before-code hook
\titlespacing*@{\section@}
  @{-1pc@}@{18pt@}@{10pt@}[10pc]
@end example

@noindent
That puts the section number in the margin.


@node \subsection
@section @code{\subsection}

@findex \subsection
@cindex subsection

Synopsis, one of:

@example
\subsection@{@var{title}@}
\subsection*@{@var{title}@}
\subsection[@var{toc-title}]@{@var{title}@}
@end example

Start a subsection.  The standard @LaTeX{} classes @code{article},
@code{book}, and @code{report} all have this command.

This produces a subsection.

@example
We will show that there are more functions than Turing machines and that
therefore some functions have no associated machine.

\subsection@{Cardinality@} We will begin with two paradoxes that
dramatize the challenge to our intuition posed by comparing the sizes of
infinite sets.
@end example

For the standard @LaTeX{} classes @code{book} and @code{report} the
default output is like @samp{1.2.3 @var{title}} (for chapter@tie{}1,
section@tie{}2, subsection@tie{}3), alone on its line and flush left, in
boldface and a larger type (the type size is @code{\large}).  The same
holds in @code{article} except that there are no chapters in that class
so it looks like @samp{2.3 @var{title}}.

The @code{*}@tie{}form shows @var{title}.
But it does not show the section number, does not increment the
@code{section} counter, and produces no table of contents entry.

The optional argument @var{toc-title} will appear as the section title
in the table of contents (@pxref{Table of contents etc.}).  If it is
not present then @var{title} will be there.  This shows the full name in
the title of the section,

@example
\subsection[$\alpha,\beta,\gamma$ paper]@{\textit@{The Origin of
  Chemical Elements@} by R.A.~Alpher, H.~Bethe, and G.~Gamow@}
@end example

@noindent
but only @samp{@BES{03B1,\alpha},@BES{03B2,\beta},@BES{03B3,\gamma}
paper} on the contents page.

For determining which sectional units are numbered and which appear in
the table of contents, the level number of a subsection is@tie{}2
(@pxref{Sectioning/secnumdepth} and @pxref{Sectioning/tocdepth}).

@PkgIndex{indentfirst}
The paragraph that follows the subsection title is not indented, as is a
standard typographical practice.  One way to get an indent is to use the
package @file{indentfirst}.

@PkgIndex{titlesec}
There are a number of ways to change the behavior of the
@code{\subsection} command.  One is the @code{\@@startsection} command
(@pxref{\@@startsection}).  There are also many packages on CTAN that
address this, including @file{titlesec}.  See the documentation but the
example below gives a sense of what they can do.

@example
\usepackage@{titlesec@}   % in preamble
\titleformat@{\subsection@}[runin]
  @{\normalfont\normalsize\bfseries@}  % format of the title
  @{\thesubsection@}                   % label
  @{0.6em@}                            % space between label and title
  @{@}                                 % before-code hook
@end example

@noindent
That puts the subsection number and @var{title} in the first line of
text.


@node \subsubsection & \paragraph & \subparagraph

@section @code{\subsubsection}, @code{\paragraph}, @code{\subparagraph}

@findex \subsubsection
@cindex subsubsection
@findex \paragraph
@cindex paragraph
@findex \subparagraph
@cindex subparagraph

Synopsis, one of:

@example
\subsubsection@{@var{title}@}
\subsubsection*@{@var{title}@}
\subsubsection[@var{toc-title}]@{@var{title}@}
@end example

@noindent
or one of:

@example
\paragraph@{@var{title}@}
\paragraph*@{@var{title}@}
\paragraph[@var{toc-title}]@{@var{title}@}
@end example

@noindent
or one of:

@example
\subparagraph@{@var{title}@}
\subparagraph*@{@var{title}@}
\subparagraph[@var{toc-title}]@{@var{title}@}
@end example

Start a subsubsection, paragraph, or subparagraph.  The standard
@LaTeX{} classes @code{article}, @code{book}, and @code{report} all have
these commands, although they are not commonly used.

This produces a subsubsection.

@example
\subsubsection@{Piston ring compressors: structural performance@}
Provide exterior/interior wall cladding assemblies
capable of withstanding the effects of load and stresses from 
consumer-grade gasoline engine piston rings.
@end example

The default output of each of the three does not change over the
standard @LaTeX{} classes @code{article}, @code{book}, and
@code{report}.  For @code{\subsubsection} the @var{title} is alone on
its line, in boldface and normal size type.  For @code{\paragraph} the
@var{title} is inline with the text, not indented, in boldface and
normal size type.  For @code{\subparagraph} the @var{title} is inline
with the text, with a paragraph indent, in boldface and normal size type
(Because an @code{article} has no chapters its subsubsections are
numbered and so it looks like @samp{1.2.3 @var{title}}, for
section@tie{}1, subsection@tie{}2, and subsubsection@tie{}3.  The other
two divisions are not numbered.)

The @code{*}@tie{}form shows @var{title}.  But it does not increment the
associated counter and produces no table of contents entry (and does not
show the number for @code{\subsubsection}).

The optional argument @var{toc-title} will appear as the division title
in the table of contents (@pxref{Table of contents etc.}).  If it is
not present then @var{title} will be there.

For determining which sectional units are numbered and which appear in
the table of contents, the level number of a subsubsection is@tie{}3, of
a paragraph is@tie{}4, and of a subparagraph is@tie{}5
(@pxref{Sectioning/secnumdepth} and @pxref{Sectioning/tocdepth}).

@PkgIndex{indentfirst}
The paragraph that follows the subsubsection title is not indented, as is a
standard typographical practice.  One way to get an indent is to use the
package @file{indentfirst}.

@PkgIndex{titlesec}
There are a number of ways to change the behavior of the these commands.
One is the @code{\@@startsection} command (@pxref{\@@startsection}).
There are also many packages on CTAN that address this, including
@file{titlesec}.  See the documentation on CTAN.


@node \appendix

@section @code{\appendix}

@findex \appendix
@cindex appendix
@cindex appendices

Synopsis:

@example
\appendix
@end example

This does not directly produce any output.  But in a book or report it
declares that subsequent @code{\chapter} commands start an appendix.  In
an article it does the same, for @code{\section} commands.  It also
resets the @code{chapter} and @code{section} counters to@tie{}0 in a
book or report, and in an article resets the @code{section} and
@code{subsection} counters.

In this book

@example
\chapter@{One@}  ...
\chapter@{Two@}  ...
 ...
\appendix
\chapter@{Three@}  ...
\chapter@{Four@}  ...
@end example

@noindent
the first two will generate output numbered @samp{Chapter 1} and
@samp{Chapter 2}.  After the @code{\appendix} the numbering will be
@samp{Appendix A} and @samp{Appendix B}.  @xref{Larger book template}
for another example.

@PkgIndex{appendix} The @file{appendix} package adds the command
@code{\appendixpage} to put a separate @samp{Appendices} in the document
body before the first appendix, and the command @code{\addappheadtotoc}
to do the same in the table of contents.  You can reset the name
@samp{Appendix} with a command like
@code{\renewcommand@{\appendixname@}@{Specification@}}, as well as a
number of other features.  See the documentation on CTAN.


@node \frontmatter & \mainmatter & \backmatter

@section @code{\frontmatter}, @code{\mainmatter}, @code{\backmatter}

@findex \frontmatter
@cindex book, front matter
@findex \mainmatter
@cindex book, main matter
@findex \backmatter
@cindex book, back matter
@cindex book, end matter

Synopsis, one of:

@example
\frontmatter
\mainmatter
\backmatter
@end example

Format a @code{book} class document differently according to which part
of the document is being produced.  All three commands are optional.

Traditionally, a book's front matter contains such things as the title
page, an abstract, a table of contents, a preface, a list of notations,
a list of figures, and a list of tables.  (Some of these front matter
pages, such as the title page, are traditionally not numbered.)  The
back matter may contain such things as a glossary, notes, a
bibliography, and an index.

The @code{\frontmatter} declaration makes the pages numbered in
lowercase roman, and makes chapters not numbered, although each
chapter's title appears in the table of contents; if you use other
sectioning commands here, use the @code{*}-version (@pxref{Sectioning}).
The @code{\mainmatter} changes the behavior back to the expected
version, and resets the page number.  The @code{\backmatter} leaves the
page numbering alone but switches the chapters back to being not
numbered.  @xref{Larger book template} for an example using the three.


@node \@@startsection
@section @code{\@@startsection}

@findex \@@startsection
@cindex section, redefining

Synopsis:

@example
\@@startsection@{@var{name}@}@{@var{level}@}@{@var{indent}@}@{@var{beforeskip}@}@{@var{afterskip}@}@{@var{style}@}
@end example

Used to help redefine the behavior of commands that start sectioning
divisions such as @code{\section} or @code{\subsection}.

Note that the @file{titlesec} package makes manipulation of sectioning
easier.  Further, while most requirements for sectioning commands can be
satisfied with @code{\@@startsection}, some cannot.  For instance, in
the standard @LaTeX{} @code{book} and @code{report} classes the commands
@code{\chapter} and @code{\report} are not constructed in this way.  To
make such a command you may want to use the @code{\secdef} command.
@c xx define, and make a cross reference to, secdef.

Technically, @code{\@@startsection} has the form

@example
\@@startsection@{@var{name}@}
  @{@var{level}@}
  @{@var{indent}@}
  @{@var{beforeskip}@}
  @{@var{afterskip}@}
  @{@var{style}@}*[@var{toctitle}]@{@var{title}@}
@end example

@noindent
so that issuing

@example
\renewcommand@{\section@}@{\@@startsection@{@var{name}@}
  @{@var{level}@}
  @{@var{indent}@}
  @{@var{beforeskip}@}
  @{@var{afterskip}@}
  @{@var{style}@}@}
@end example

@noindent
redefines @code{\section} to have the form
@code{\section*[@var{toctitle}]@{@var{title}@}} (here too, the
star@tie{}@code{*} is optional).  @xref{Sectioning}.  This implies that
when you write a command like @code{\renewcommand@{section@}@{...@}},
the @code{\@@startsection@{...@}} must come last in the definition.  See
the examples below.

@table @var

@item name
@anchor{startsection name}
@anchor{\@@startsection/name}
Name of the counter used to number the sectioning header.  This counter
must be defined separately.  Most commonly this is either
@code{section}, @code{subsection}, or @code{paragraph}.  Although in
those cases the counter name is the same as the sectioning command
itself, you don't have to use the same name.

Then @code{\the}@var{name} displays the title number and
@code{\}@var{name}@code{mark} is for the page headers.  See the third
example below.

@item level
@anchor{startsection level}
@anchor{\@@startsection/level}
An integer giving the depth of the sectioning command.
@xref{Sectioning} for the list of standard level numbers.

If @var{level} is less than or equal to the value of the counter
@code{secnumdepth} then titles for this sectioning command will be
numbered (@pxref{Sectioning/secnumdepth}).  For instance, if
@code{secnumdepth} is 1 in an @code{article} then the command
@code{\section@{Introduction@}} will produce output like ``1
Introduction'' while @code{\subsection@{Discussion@}} will produce
output like ``Discussion'', without the number prefix.

If @var{level} is less than or equal to the value of the counter
@var{tocdepth} then the table of contents will have an entry for this
sectioning unit (@pxref{Sectioning/tocdepth}).  For instance, in an
@code{article}, if @var{tocdepth} is 1 then the table of contents will
list sections but not subsections.

@item indent
@anchor{startsection indent}
@anchor{\@@startsection/indent}
A length giving the indentation of all of the title lines with respect
to the left margin.  To have the title flush with the margin use
@code{0pt}.  A negative indentation such as @code{-\parindent} will move
the title into the left margin.

@item beforeskip
@anchor{startsection beforeskip}
@anchor{\@@startsection/beforeskip}
The absolute value of this length is the amount of vertical space that
is inserted before this sectioning unit's title.  This space will be
discarded if the sectioning unit happens to start at the top of a fresh
page.  If this number is negative then the first paragraph following the
header is not indented, if it is non-negative then the first paragraph
is indented.  (Note that the negative of @code{1pt plus 2pt minus 3pt}
is @code{-1pt plus -2pt minus -3pt}.)

For example, if @var{beforeskip} is @code{-3.5ex plus -1ex minus -0.2ex}
then to start the new sectioning unit, @LaTeX{} will add about 3.5 times
the height of a letter x in vertical space, and the first paragraph in
the section will not be indented.  Using a rubber length, with
@code{plus} and @code{minus}, is good practice here since it gives
@LaTeX{} more flexibility in making up the page (@pxref{Lengths}).

The full accounting of the vertical space between the baseline of the
line prior to this sectioning unit's header and the baseline of the
header is that it is the sum of the @code{\parskip} of the text font,
the @code{\baselineskip} of the title font, and the absolute value of
the @var{beforeskip}.  This space is typically rubber so it may stretch
or shrink.  (If the sectioning unit starts on a fresh page so that the
vertical space is discarded then the baseline of the header text will be
where @LaTeX{} would put the baseline of the first text line on that
page.)

@item afterskip
@anchor{startsection afterskip}
@anchor{\@@startsection/afterskip}
This is a length.  If @var{afterskip} is non-negative then this is the
vertical space inserted after the sectioning unit's title header.  If it
is negative then the title header becomes a run-in header, so that it
becomes part of the next paragraph.  In this case the absolute value of
the length gives the horizontal space between the end of the title and
the beginning of the following paragraph.  (Note that the negative of
@code{1pt plus 2pt minus 3pt} is @code{-1pt plus -2pt minus -3pt}.)

As with @var{beforeskip}, using a rubber length, with @code{plus} and
@code{minus} components, is good practice here since it gives @LaTeX{}
more flexibility in putting together the page.

If @code{afterskip} is non-negative then the full accounting of the
vertical space between the baseline of the sectioning unit's header and
the baseline of the first line of the following paragraph is that it is
the sum of the @code{\parskip} of the title font, the
@code{\baselineskip} of the text font, and the value of @var{after}.
That space is typically rubber so it may stretch or shrink.  (Note that
because the sign of @code{afterskip} changes the sectioning unit
header's from standalone to run-in, you cannot use a negative
@code{afterskip} to cancel part of the @code{\parskip}.)

@item style
@anchor{startsection style}
@anchor{\@@startsection/style}
Controls the styling of the title.  See the examples below.  Typical
commands to use here are @code{\centering}, @code{\raggedright},
@code{\normalfont}, @code{\hrule}, or @code{\newpage}.  The last command
in @var{style} may be one that takes one argument, such as
@code{\MakeUppercase} or @code{\fbox} that takes one argument.  The
section title will be supplied as the argument to this command. For
instance, setting @var{style} to @code{\bfseries\MakeUppercase} would
produce titles that are bold and uppercase.
@end table

These are @LaTeX{}'s defaults for the first three sectioning units that
are defined with @code{\@@startsection}, for the @file{article},
@file{book}, and @file{report} classes.  For section, the @var{level} is
1, the @var{indent} is 0@dmn{pt}, the @var{beforeskip} is @code{-3.5ex
plus -1ex minus -0.2ex}, the @var{afterskip} is @code{2.3ex plus 0.2ex},
and the @var{style} is @code{\normalfont\Large\bfseries}.  For
subsection, the @var{level} is 2, the @var{indent} is 0@dmn{pt}, the
@var{beforeskip} is @code{-3.25ex plus -1ex minus -0.2ex}, the
@var{afterskip} is @code{1.5ex plus 0.2ex}, and the @var{style} is
@code{\normalfont\large\bfseries}.  For subsubsection, the @var{level}
is 3, the @var{indent} is 0@dmn{pt}, the @var{beforeskip} is
@code{-3.25ex plus -1ex minus -0.2ex}, the @var{afterskip} is
@code{1.5ex plus 0.2ex}, and the @var{style} is
@code{\normalfont\normalsize\bfseries}.

Here are examples.  They go either in a package or class file or in the
preamble of a @LaTeX{} document.  If you put them in the preamble they
must go between a @code{\makeatletter} command and a
@code{\makeatother}.  (Probably the error message @code{You can't use
`\spacefactor' in vertical mode.}  means that you forgot this.)
@xref{\makeatletter & \makeatother}.

This will put section titles in large boldface type, centered.  It says
@code{\renewcommand} because @LaTeX{}'s standard classes have already
defined a @code{\section}.  For the same reason it does not define a
@code{section} counter, or the commands @code{\thesection} and
@code{\l@@section}.

@example
\renewcommand\section@{%
  \@@startsection@{section@}% @ref{\@@startsection/name,@var{name},@var{name}}
    @{1@}% @ref{\@@startsection/level,@var{level},@var{level}}
    @{0pt@}% @ref{\@@startsection/indent,@var{indent},@var{indent}}
    @{-3.5ex plus -1ex minus -.2ex@}% @ref{\@@startsection/beforeskip,@var{beforeskip},@var{beforeskip}}
    @{2.3ex plus.2ex@}% @ref{\@@startsection/afterskip,@var{afterskip},@var{afterskip}}
    @{\centering\normalfont\Large\bfseries@}% @ref{\@@startsection/style,@var{style},@var{style}}
  @}
@end example

This will put @code{subsection} titles in small caps type, inline with the paragraph.

@example
\renewcommand\subsection@{%
  \@@startsection@{subsection@}%  @ref{\@@startsection/name,@var{name},@var{name}}
    @{2@}% @ref{\@@startsection/level,@var{level},@var{level}}
    @{0em@}% @ref{\@@startsection/indent,@var{indent},@var{indent}}
    @{-1ex plus 0.1ex minus -0.05ex@}% @ref{\@@startsection/beforeskip,@var{beforeskip},@var{beforeskip}}
    @{-1em plus 0.2em@}% @ref{\@@startsection/afterskip,@var{afterskip},@var{afterskip}}
    @{\scshape@}% @ref{\@@startsection/style,@var{style},@var{style}}
  @}
@end example

The prior examples redefined existing sectional unit title commands.
This defines a new one, illustrating the needed counter and macros to
display that counter.

@c From https://groups.google.com/forum/#!searchin/comp.text.tex/startsection%7Csort:relevance/comp.text.tex/sB-nTS-oL08/ZZeKYdG0llMJ
@example
\setcounter@{secnumdepth@}@{6@}% show counters this far down
\newcounter@{subsubparagraph@}[subparagraph]% counter for numbering
\renewcommand@{\thesubsubparagraph@}%               how to display 
  @{\thesubparagraph.\@@arabic\c@@subsubparagraph@}%  numbering
\newcommand@{\subsubparagraph@}@{\@@startsection
                         @{subsubparagraph@}%
                         @{6@}%
                         @{0em@}%
                         @{\baselineskip@}%
                         @{0.5\baselineskip@}%
                         @{\normalfont\normalsize@}@}
\newcommand*\l@@subsubparagraph@{\@@dottedtocline@{6@}@{10em@}@{5em@}@}% for toc
\newcommand@{\subsubparagraphmark@}[1]@{@}% for page headers
@end example


@node Cross references
@chapter Cross references

@cindex cross references

@cindex label
We often want something like @samp{See Theorem~31}.  But by-hand typing
the 31 is poor practice.  Instead you should write a @dfn{label} such as
@code{\label@{eq:GreensThm@}} and then @dfn{reference} it, as with
@code{See equation~\ref@{eq:GreensThm@}}.  @LaTeX{} will automatically
work out the number, put it into the output, and will change that number
later if needed.

@example
We will see this with Theorem~\ref@{th:GreensThm@}. % forward reference
...
\begin@{theorem@} \label@{th:GreensThm@}
  ...
\end@{theorem@}
...
See Theorem~\ref@{th:GreensThm@} on page~\pageref@{th:GreensThm@}.
@end example

@LaTeX{} tracks cross reference information in a file having the
extension @file{.aux} and with the same base name as the file containing
the @code{\label}.  So if @code{\label} is in @file{calculus.tex} then
the information is in @file{calculus.aux}.  @LaTeX{} puts the
information in that file every time it runs across a @code{\label}.

@cindex forward reference
@cindex reference, forward
The behavior described in the prior paragraph results in a quirk that
happens when your document has a @dfn{forward reference}, a @code{\ref}
that appears before the associated @code{\label}.  If this is the first
time that you are compiling the document then you will get @samp{LaTeX
Warning: Label(s) may have changed. Rerun to get cross references right}
and in the output the forward reference will appear as two question
marks@tie{}@samp{??}, in boldface.  A similar thing happens if you
change some things so the references changes; you get the same warning
and the output contains the old reference information.  In both cases,
resolve this by compiling the document a second time.

@PkgIndex{cleveref} The @code{cleveref} package enhances @LaTeX{}'s
cross referencing features.  You can arrange that if you enter
@code{\begin@{thm@}\label@{th:Nerode@}...\end@{thm@}} then
@code{\cref@{th:Nerode@}} will output @samp{Theorem 3.21}, without you
having to enter the ``Theorem.''

@menu
* \label::      Assign a symbolic name to a piece of text.
* \pageref::    Refer to a page number.
* \ref::        Refer to a section, figure or similar.
@end menu


@node \label
@section @code{\label}

@findex \label

Synopsis:

@example
\label@{@var{key}@}
@end example

Assign a reference number to @var{key}.  In ordinary text
@code{\label@{@var{key}@}} assigns to @var{key} the number of the
current sectional unit. Inside an environment with numbering, such as a
@code{table} or @code{theorem} environment, @code{\label@{@var{key}@}}
assigns to @var{key} the number of that environment.  Retrieve the
assigned number with the @code{\ref@{@var{key}@}} command
(@pxref{\ref}).

A key name can consist of any sequence of letters, digits, or common
punctuation characters.  Upper and lowercase letters are
distinguished, as usual.

A common convention is to use labels consisting of a prefix and a suffix
separated by a colon or period.  Thus, @code{\label@{fig:Post@}} is a
label for a figure with a portrait of Emil Post.  This helps to avoid
accidentally creating two labels with the same name, and makes your
source more readable.  Some commonly-used prefixes:

@table @code
@item ch
for chapters

@item sec
@itemx subsec
for lower-level sectioning commands

@item fig
for figures

@item tab
for tables

@item eq
for equations
@end table

In the auxiliary file the reference information is kept as the text of
a command of the form
@code{\newlabel@{@var{label}@}@{@{@var{currentlabel}@}@{@var{pagenumber}@}@}}.
Here @var{currentlabel} is the current value of the macro
@code{\@@currentlabel} that is usually updated whenever you call
@code{\refstepcounter@{@var{counter}@}}.

Below, the key @code{sec:test} will get the number of the current
section and the key @code{fig:test} will get the number of the figure.
(Incidentally, put labels after captions in figures and tables.)

@example
\section@{section name@}
\label@{sec:test@}
This is Section~\ref@{sec:test@}.
\begin@{figure@}
  ...
  \caption@{caption text@}
  \label@{fig:test@}
\end@{figure@}
See Figure~\ref@{fig:test@}.
@end example


@node \pageref
@section @code{\pageref}

@findex \pageref
@cindex cross referencing with page number
@cindex page number, cross referencing

Synopsis:

@example
\pageref@{@var{key}@}
@end example

Produce the page number of the place in the text where the corresponding
@code{\label}@{@var{key}@} command appears.

If there is no @code{\label@{@var{key}@}} then you get something like
@samp{LaTeX Warning: Reference `th:GrensThm' on page 1 undefined on
input line 11.}

Below, the @code{\label@{eq:main@}} is used both for the formula number
and for the page number.  (Note that the two references are forward
references so this document would need to be compiled twice to resolve
those.)

@example
The main result is formula~\ref@{eq:main@} on page~\pageref@{eq:main@}.
  ...
\begin@{equation@} \label@{eq:main@}
   \mathbf@{P@}=\mathbf@{NP@}
\end@{equation@}
@end example


@node \ref
@section @code{\ref}

@findex \ref
@cindex cross referencing, symbolic
@cindex section number, cross referencing
@cindex equation number, cross referencing
@cindex figure number, cross referencing
@cindex footnote number, cross referencing

Synopsis:

@example
\ref@{@var{key}@}
@end example

Produces the number of the sectional unit,
equation, footnote, figure, @dots{}, of the corresponding
@code{\label} command (@pxref{\label}).  It does not produce any text,
such as the word `Section' or `Figure', just the bare number itself.

If there is no @code{\label@{@var{key}@}} then you get something like
@samp{LaTeX Warning: Reference `th:GrensThm' on page 1 undefined on
input line 11.}

In this example the @code{\ref@{popular@}} produces @samp{2}.  Note that
it is a forward reference since it comes before @code{\label@{popular@}}
so this document would have to be compiled twice.

@example
The most widely-used format is item number~\ref@{popular@}.
\begin@{enumerate@}
\item Plain \TeX
\item \label@{popular@} \LaTeX
\item Con\TeX t
\end@{enumerate@}
@end example

@PkgIndex{cleveref}
The @file{cleveref} package includes text such as @samp{Theorem} in the
reference.  See the documentation on CTAN.


@node Environments
@chapter Environments

@cindex environments
@findex \begin
@findex \end

@LaTeX{} provides many environments for delimiting certain behavior.
An environment begins with @code{\begin} and ends with @code{\end},
like this:

@example
\begin@{@var{environment-name}@}
  ...
\end@{@var{environment-name}@}
@end example

The @var{environment-name} at the beginning must exactly match that at
the end. For instance, the input
@code{\begin@{table*@}...\end@{table@}} will cause an error like:
@samp{! LaTeX Error: \begin@{table*@} on input line 5 ended by
\end@{table@}.}

@cindex group, and environments
Environments are executed within a group.

@menu
* abstract::              Produce an abstract.
* array::                 Math arrays.
* center::                Centered lines.
* description::           Labelled lists.
* displaymath::           Formulas that appear on their own line.
* document::              Enclose the whole document.
* enumerate::             Numbered lists.
* eqnarray::              Sequences of aligned equations.
* equation::              Displayed equation.
* figure::                Floating figures.
* filecontents::          Writing multiple files from the source.
* flushleft::             Flushed left lines.
* flushright::            Flushed right lines.
* itemize::               Bulleted lists.
* letter::                Letters.
* list::                  Generic list environment.
* math::                  In-line math.
* minipage::              Miniature page.
* picture::               Picture with text, arrows, lines and circles.
* quotation & quote::     Include a quotation.
* tabbing::               Align text arbitrarily.
* table::                 Floating tables.
* tabular::               Align text in columns.
* thebibliography::      Bibliography or reference list.
* theorem::               Theorems, lemmas, etc.
* titlepage::             For hand crafted title pages.
* verbatim::              Simulating typed input.
* verse::                 For poetry and other things.
@end menu


@node abstract
@section @code{abstract}

@EnvIndex{abstract}
@cindex abstracts

Synopsis:

@example
\begin@{abstract@}
...
\end@{abstract@}
@end example

Produce an abstract, possibly of multiple paragraphs.  This environment
is only defined in the @code{article} and @code{report} document classes
(@pxref{Document classes}).

Using the example below in the @code{article} class produces a displayed
paragraph.  Document class option @code{titlepage} causes the abstract
to be on a separate page (@pxref{Document class options}); this is the
default only in the @code{report} class.

@example
\begin@{abstract@}
  We compare all known accounts of the proposal made by Porter Alexander 
  to Robert E Lee at the Appomattox Court House that the army continue
  in a guerrilla war, which Lee refused.
\end@{abstract@}
@end example

The next example produces a one column abstract in a two column document (for
a more flexible solution, use the package @file{abstract}).

@c Adopted from http://www.tex.ac.uk/FAQ-onecolabs.html
@example
\documentclass[twocolumn]@{article@}
  ...
\begin@{document@}
\title@{Babe Ruth as Cultural Progenitor: a Atavistic Approach@}
\author@{Smith \\ Jones \\ Robinson\thanks@{Railroad tracking grant.@}@}
\twocolumn[
  \begin@{@@twocolumnfalse@}
     \maketitle
     \begin@{abstract@}
       Ruth was not just the Sultan of Swat, he was the entire swat
       team.   
     \end@{abstract@}
   \end@{@@twocolumnfalse@}
   ]
@{   % by-hand insert a footnote at page bottom
 \renewcommand@{\thefootnote@}@{\fnsymbol@{footnote@}@}
 \footnotetext[1]@{Thanks for all the fish.@}
@}
@end example


@node array
@section @code{array}

@EnvIndex{array}
@cindex arrays, math

Synopsis:

@example
\begin@{array@}@{@var{cols}@}
  @var{column 1 entry} &@var{column 2 entry} ... &@var{column n entry} \\
  ...
\end@{array@}
@end example

@noindent
or:

@example
\begin@{array@}[@var{pos}]@{@var{cols}@}
  @var{column 1 entry} &@var{column 2 entry} ... &@var{column n entry} \\
  ...
\end@{array@}
@end example

Produce a mathematical array.  This environment can only be used in math
mode, and normally appears within a displayed mathematics environment
such as @code{equation} (@pxref{equation}).  Inside of each row the
column entries are separated by an ampersand, (@code{&}).  Rows are
terminated with double-backslashes (@pxref{\\}).

This example shows a three by three array.

@example
\begin@{equation*@}
  \chi(x) =
  \left|              % vertical bar fence
    \begin@{array@}@{ccc@}
      x-a  &-b  &-c  \\
      -d   &x-e &-f  \\
      -g   &-h  &x-i
    \end@{array@}
 \right|
\end@{equation*@}
@end example

The required argument @var{cols} describes the number of columns, their
alignment, and the formatting of the intercolumn regions.  For instance,
@code{\begin@{array@}@{rcl@}...\end@{array@}} gives three columns: the
first flush right, the second centered, and the third flush left.  See
@ref{tabular} for the complete description of @var{cols} and of the
other common features of the two environments, including the optional
@var{pos} argument.

There are two ways that @code{array} diverges from @code{tabular}.  The
first is that @code{array} entries are typeset in math mode, in
textstyle (@pxref{Modes}) except if the @var{cols} definition specifies
the column with @code{p@{...@}}, which causes the entry to be typeset in
text mode.  The second is that, instead of @code{tabular}'s parameter
@code{\tabcolsep}, @LaTeX{}'s intercolumn space in an @code{array} is
governed by
@findex \arraycolsep
@code{\arraycolsep}, which gives half the width between columns. The
default for this is @samp{5pt} so that between two columns comes
10@dmn{pt} of space.

@PkgIndex{amsmath}
To obtain arrays with braces the standard is to use the @file{amsmath}
package.  It comes with environments @code{pmatrix} for an array
surrounded by parentheses@tie{}@code{(...)}, @code{bmatrix} for an array
surrounded by square brackets@tie{}@code{[...]}, @code{Bmatrix} for an
array surrounded by curly braces@tie{}@code{@{...@}}, @code{vmatrix} for
an array surrounded by vertical bars@tie{}@code{|...|}, and
@code{Vmatrix} for an array surrounded by double vertical
bars@tie{}@code{||...||}, along with a number of other array constructs.

@PkgIndex{amsmath}
The next example uses the @file{amsmath} package.

@example
\usepackage@{amsmath@}  % in preamble

\begin@{equation@}    
  \begin@{vmatrix@}@{cc@}  % array with vert lines
    a  &b \\
    c  &d       
  \end@{vmatrix@}=ad-bc
\end@{equation@}
@end example

@PkgIndex{array (package)}
@PkgIndex{dcolumn}
There are many packages concerning arrays.  The @file{array} package has
many useful extensions, including more column types.  The @file{dcolumn}
package adds a column type to center on a decimal point.  For both see
the documentation on CTAN.


@node center
@section @code{center}

@EnvIndex{center}
@cindex centering text, environment for

Synopsis:

@example
\begin@{center@}
  @var{line1} \\
  @var{line2} \\
  ...
\end@{center@}
@end example

Create a new paragraph consisting of a sequence of lines that are
centered within the left and right margins.  Use
double-backslash, @code{\\}, to get a line break (@pxref{\\}).
@findex \\ @r{(for @code{center})}
If some text is too long to fit on a line then @LaTeX{} will insert line
breaks that avoid hyphenation and avoid stretching or shrinking any
interword space.

This environment inserts space above and below the text body.  See
@ref{\centering} to avoid such space, for example inside a @code{figure}
environment.

This example produces three centered lines.  There is extra vertical
space between the last two lines.

@example
\begin@{center@}
  A Thesis Submitted in Partial Fufillment \\
  of the Requirements of \\[0.5ex]
  the School of Environmental Engineering
\end@{center@}
@end example

In this example, depending on the page's line width, @LaTeX{} may choose
a line break for the part before the double backslash.  If so, it will
center each of the two lines and if not it will center the single line.
Then @LaTeX{} will break at the double backslash, and will center the
ending.

@example
\begin@{center@}
  My father considered that anyone who went to chapel and didn't drink 
  alcohol was not to be tolerated.\\ 
  I grew up in that belief.  --Richard Burton 
\end@{center@}
@end example

A double backslash after the final line is optional.  If present it
doesn't add any vertical space.

In a two-column document the text is centered in a column, not in the
entire page.

@menu
* \centering::          Declaration form of the @code{center} environment.
@end menu


@node \centering
@subsection @code{\centering}

@findex \centering
@cindex centering text, declaration for


Synopsis:

@example
@{\centering ... @}
@end example

@noindent
or

@example
\begin@{group@}
  \centering ...
\end@{group@}
@end example

Center the material in its scope.  It is most often used inside an
environment such as @code{figure}, or in a @code{parbox}.

This example's @code{\centering} declaration causes the graphic to be
horizontally centered.

@example
\begin@{figure@}
  \centering
  \includegraphics[width=0.6\textwidth]@{ctan_lion.png@}
  \caption@{CTAN Lion@}  \label@{fig:CTANLion@}
\end@{figure@}
@end example

@noindent
The scope of this @code{\centering} ends with the @code{\end@{figure@}}.

Unlike the @code{center} environment, the @code{\centering} command does
not add vertical space above and below the text.  That's its advantage
in the above example; there is not an excess of space.

It also does not start a new paragraph; it simply changes how @LaTeX{}
formats paragraph units.  If @code{ww @{\centering xx \\ yy@} zz} is
surrounded by blank lines then @LaTeX{} will create a paragraph whose
first line @samp{ww xx} is centered and whose second line, not centered,
contains @samp{yy zz}.  Usually what is desired is for the scope of the
declaration to contain a blank line or the @code{\end} command of an
environment such as @code{figure} or @code{table} that ends the
paragraph unit.  Thus, if @code{@{\centering xx \\ yy\par@} zz} is
surrounded by blank lines then it makes a new paragraph with two
centered lines @samp{xx} and @samp{yy}, followed by a new paragraph with
@samp{zz} that is formatted as usual.


@node description
@section @code{description}

@EnvIndex{description}
@cindex labelled lists, creating
@cindex description lists, creating

Synopsis:

@example
\begin@{description@}
  \item[@var{label of first item}] @var{text of first item}
  \item[@var{label of second item}] @var{text of second item}
   ...
\end@{description@}
@end example

Environment to make a list of labeled items.  Each item's @var{label} is
typeset in bold and is flush left, so that long labels continue into the
first line of the item text.  There must be at least one item; having
none causes the @LaTeX{} error @samp{Something's wrong--perhaps a
missing \item}.

This example shows the environment used for a sequence of definitions.

@example
\begin@{definition@}
  \item[lama] A priest.
  \item[llama] A beast.
\end@{definition@}
@end example

@noindent
The labels @samp{lama} and @samp{llama} are output in boldface, with the
left edge on the left margin.

@findex \item
Start list items with the @code{\item} command (@pxref{\item}).  Use the
optional labels, as in @code{\item[Main point]}, because there is
no sensible default.  Following the @code{\item} is optional text, which
may contain multiple paragraphs.

@cindex bold typewriter, avoiding
@cindex typewriter labels in lists
Since the labels are in bold style, if the label text calls for a font
change given in argument style (see @ref{Font styles}) then it will come
out bold.  For instance, if the label text calls for typewriter with
@code{\item[\texttt@{label text@}]} then it will appear in bold
typewriter, if that is available. The simplest way around this, in this
example to get non-bold typewriter, is to use declarative style:
@code{\item[@{\tt label text@}]}.  Similarly, get the standard roman
font with @code{\item[@{\rm label text@}]}.

For other major @LaTeX{} labelled list environments, see @ref{itemize}
and @ref{enumerate}.  Unlike those environments, nesting
@code{description} environments does not change the default label; it is
boldface and flush left at all levels.

For information about list layout parameters, including the default
values, and for information about customizing list layout, see
@ref{list}.  The package @file{enumitem} is useful for customizing
lists.

This example changes the description labels to small caps.

@example
\renewcommand@{\descriptionlabel@}[1]@{%
  @{\hspace@{\labelsep@}\textsc@{#1@}@}@}
@end example


@node displaymath
@section @code{displaymath}
@c http://tex.stackexchange.com/questions/40492/what-are-the-differences-between-align-equation-and-displaymath

@EnvIndex{displaymath}

Synopsis:

@example
\begin@{displaymath@}
  @var{mathematical text}
\end@{displaymath@}
@end example

Environment to typeset the math text on its own line, in display style
and centered.  To make the text be flush-left use the global option
@code{fleqn}; see @ref{Document class options}.

In the @code{displaymath} environment no equation number is added to the
math text. One way to get an equation number is to use the
@code{equation} environment (@pxref{equation}).

@LaTeX{} will not break the @var{math text} across lines.

@PkgIndex{amsmath}
Note that the @file{amsmath} package has significantly more extensive
displayed equation facilities.  For example, there are a number of
ways in that package for having math text broken across lines.

The construct @code{\[@var{math text}\]} is essentially a synonym for
@code{\begin@{displaymath@}@var{math text}\end@{displaymath@}} but the
latter is easier to work with in the source file; for instance,
searching for a square bracket may get false positives but the word
@code{displaymath} will likely be unique.  (The construct
@code{$$@var{math text}$$} from Plain@tie{}@TeX{} is sometimes
mistakenly used as a synonym for @code{displaymath}.  It is not a
synonym, because the @code{displaymath} environment checks that it isn't
started in math mode and that it ends in math mode begun by the matching
environment start, because the @code{displaymath} environment has
different vertical spacing, and because the @code{displaymath}
environment honors the @code{fleqn} option.)

The output from this example is centered and alone on its line. 

@example
\begin@{displaymath@}
  \int_1^2 x^2\,dx=7/3
\end@{displaymath@}
@end example

@noindent
Also, the integral sign is larger than the inline version  
@code{\( \int_1^2 x^2\,dx=7/3 \)} produces.


@node document
@section @code{document}

@EnvIndex{document}

The @code{document} environment encloses the entire body of a document.
It is required in every @LaTeX{} document.  @xref{Starting and ending}.

@menu
* \AtBeginDocument::          Hook for commands at the start of the document.
* \AtEndDocument::            Hook for commands at the end of the document.
@end menu


@node \AtBeginDocument
@subsection @code{\AtBeginDocument}

@findex \AtBeginDocument
@cindex beginning of document hook

Synopsis:

@example
\AtBeginDocument@{@var{code}@}
@end example

Save @var{code} and execute it when @code{\begin@{document@}} is
executed, at the very end of the preamble.  The code is executed after
the font selection tables have been set up, so the normal font for the
document is the current font.  However, the code is executed as part of
the preamble so you cannot do any typesetting with it.

You can issue this command more than once; the successive code lines
will be executed in the order that you gave them.


@node \AtEndDocument
@subsection @code{\AtEndDocument}

@findex \AtEndDocument
@cindex end of document hook

Synopsis:

@example
\AtEndDocument@{@var{code}@}
@end example

Save @var{code} and execute it near the end of the document.
Specifically, it is executed when @code{\end@{document@}} is executed,
before the final page is finished and before any leftover floating
environments are processed. If you want some of the code to be executed
after these two processes then include a @code{\clearpage} at the
appropriate point in @var{code}.

You can issue this command more than once; the successive code lines
will be executed in the order that you gave them.


@node enumerate
@section @code{enumerate}

@EnvIndex{enumerate}
@cindex lists of items, numbered

Synopsis:

@example
\begin@{enumerate@}
  \item[@var{optional label of first item}] @var{text of first item}
  \item[@var{optional label of second item}] @var{text of second item}
  ...
\end@{enumerate@}
@end example

Environment to produce a numbered list of items.  The format of the
label numbering depends on the nesting level of this environment; see
below. The default top-level numbering is @samp{1.}, @samp{2.},
etc. Each @code{enumerate} list environment must have at least one item;
having none causes the @LaTeX{} error @samp{Something's wrong--perhaps a
missing \item}.

This example gives the first two finishers in the 1908 Olympic marathon.
As a top-level list the labels would come out as @samp{1.} and
@samp{2.}.

@example
\begin@{enumerate@}
 \item Johnny Hayes (USA)
 \item Charles Hefferon (RSA) 
\end@{enumerate@}
@end example

@findex \item
Start list items with the @code{\item} command (@pxref{\item}).  If you
give @code{\item} an optional argument by following it with square
brackets, as in @code{\item[Interstitial label]}, then the next item
will continue the interrupted sequence (@pxref{\item}).  That is, you
will get labels like @samp{1.}, then @samp{Interstitial label}, then
@samp{2.}.  Following the @code{\item} is optional text, which may
contain multiple paragraphs.

Enumerations may be nested within other @code{enumerate} environments,
or within any paragraph-making environment such as @code{itemize}
(@pxref{itemize}), up to four levels deep.  This gives @LaTeX{}'s
default for the format at each nesting level, where 1 is the top level,
the outermost level.

@enumerate
@item arabic number followed by a period: @samp{1.}, @samp{2.},@tie{}@dots{}
@item lowercase letter inside parentheses: @samp{(a)}, @samp{(b)}@tie{}@dots{}
@item lowercase roman numeral followed by a period: @samp{i.}, @samp{ii.},@tie{}@dots{}
@item uppercase letter followed by a period: @samp{A.}, @samp{B.},@tie{}@dots{}
@end enumerate

@findex \enumi
@findex \enumii
@findex \enumiii
@findex \enumiv
@anchor{enumerate enumi}
@anchor{enumerate enumii}
@anchor{enumerate enumiii}
@anchor{enumerate enumiv}
The @code{enumerate} environment uses the counters @code{\enumi} through
@code{\enumiv} (@pxref{Counters}).

For other major @LaTeX{} labeled list environments, see
@ref{description} and @ref{itemize}.  For information about list layout
parameters, including the default values, and for information about
customizing list layout, see @ref{list}.  The package @file{enumitem} is
useful for customizing lists.

@findex \labelenumi
@findex \labelenumii
@findex \labelenumiii
@findex \labelenumiv
@anchor{enumerate labelenumi}
@anchor{enumerate labelenumii}
@anchor{enumerate labelenumiii}
@anchor{enumerate labelenumiv}
To change the format of the label use @code{\renewcommand}
(@pxref{\newcommand & \renewcommand}) on the commands @code{\labelenumi}
through @code{\labelenumiv}. For instance, this first level list will be
labelled with uppercase letters, in boldface, and without a trailing
period.

@findex \Alph @r{example}
@example
\renewcommand@{\labelenumi@}@{\textbf@{\Alph@{enumi@}@}@}
\begin@{enumerate@}
  \item Shows as boldface A
  \item Shows as boldface B
\end@{enumerate@}
@end example

For a list of counter-labeling commands see @ref{\alph \Alph \arabic
\roman \Roman \fnsymbol}.


@node eqnarray
@section @code{eqnarray}

@EnvIndex{eqnarray}
@cindex equations, aligning
@cindex aligning equations

@cindex align @r{environment, from @code{amsmath}}
@cindex amsmath @r{package, replacing @code{eqnarray}}
@cindex Madsen, Lars
The @code{eqnarray} environment is obsolete.  It has infelicities,
including spacing that is inconsistent with other mathematics elements.
(See ``Avoid eqnarray!''@: by Lars Madsen
@url{http://tug.org/TUGboat/tb33-1/tb103madsen.pdf}).  New documents
should include the @file{amsmath} package and use the displayed
mathematics environments provided there, such as the @code{align}
environment.  We include a description only for completeness and for
working with old documents.

Synopsis:

@example
\begin@{eqnarray@} 
  @var{first formula left}  &@var{first formula middle}  &@var{first formula right} \\
  ...
\end@{eqnarray@}
@end example

@noindent
or 

@example
\begin@{eqnarray*@} 
  @var{first formula left}  &@var{first formula middle}  &@var{first formula right} \\
  ...
\end@{eqnarray*@}
@end example

@findex \\ @r{(for @code{eqnarray})}
Display a sequence of equations or inequalities.  The left and right
sides are typeset in display mode, while the middle is typeset in text
mode.

It is similar to a three-column @code{array} environment, with items
within a row separated by an ampersand@tie{}(@code{&}), and with rows
separated by double backslash@tie{} @code{\\}).
@findex \\* @r{(for @code{eqnarray})}
The starred form of line break (@code{\\*}) can also be used to separate
equations, and will disallow a page break there (@pxref{\\}).

@findex \nonumber
@cindex equation numbers, omitting
The unstarred form @code{eqnarray} places an equation number on every
line (using the @code{equation} counter), unless that line contains a
@code{\nonumber} command.  The starred form @code{eqnarray*} omits
equation numbering, while otherwise being the same.

@findex \lefteqn
The command @code{\lefteqn} is used for splitting long formulas across
lines. It typesets its argument in display style flush left in a box of
zero width.

This example shows three lines.  The first two lines make an inequality,
while the third line has not entry on the left side.

@example
\begin@{eqnarray*@}
  \lefteqn@{x_1+x_2+\cdots+x_n@}     \\
    &\leq &y_1+y_2+\cdots+y_n      \\
    &=    &z+y_3+\cdots+y_n
\end@{eqnarray*@}
@end example


@node equation
@section @code{equation}

@EnvIndex{equation}
@cindex equations, environment for
@cindex formulas, environment for

Synopsis:

@example
\begin@{equation@}
  @var{mathematical text}
\end@{equation@}
@end example

The same as a @code{displaymath} environment (@pxref{displaymath})
except that @LaTeX{} puts an equation number flush to the right margin.
The equation number is generated using the @code{equation} counter.

You should have no blank lines between @code{\begin@{equation@}} and
@code{\begin@{equation@}}, or @LaTeX{} will tell you that there is a
missing dollar sign.

@PkgIndex{amsmath}
The package @file{amsmath} package has extensive displayed equation
facilities.  New documents should include this package.


@node figure
@section @code{figure}

@EnvIndex{figure}
@cindex inserting figures
@cindex figures, inserting

Synopsis:

@example
\begin@{figure@}[@var{placement}]
  @var{figure body}
  \caption[@var{loftitle}]@{@var{title}@}  % optional
  \label@{@var{label@}}              % optional
\end@{figure@}
@end example

@noindent
or:

@example
\begin@{figure*@}[@var{placement}]
  @var{figure body}
  \caption[@var{loftitle}]@{@var{title}@}  % optional
  \label@{@var{label@}}              % optional  
\end@{figure*@}
@end example

Figures are for material that is not part of the normal text.  An
example is material that you cannot have split between two pages, such
as a graphic.  Because of this, @LaTeX{} does not typeset figures in
sequence with normal text but instead ``floats'' them to a convenient
place, such as the top of a following page (@pxref{Floats}).

The @var{figure body} can consist of imported graphics
(@pxref{Graphics}), or text, @LaTeX{} commands, etc.  It is typeset in a
@code{parbox} of width @code{\textwidth}.

The possible values of @var{placement} are @code{h} for @samp{here},
@code{t} for @samp{top}, @code{b} for @samp{bottom}, and @code{p} for
@samp{on a separate page of floats}.  For the effect of these options on
the float placement algorithm, see @ref{Floats}.

The starred form @code{figure*} is used when a document is in
double-column mode (@pxref{\twocolumn}).  It produces a figure that
spans both columns, at the top of the page.  To add the possibility of
placing at a page bottom see the discussion of @var{placement} @code{b}
in @ref{Floats}.

The label is optional; it is used for cross references (@pxref{Cross
references}).
@findex \caption
The optional @code{\caption} command specifies caption text for the
figure.  By default it is numbered.  If @var{loftitle} is present, it is
used in the list of figures instead of @var{title} (@pxref{Table of
contents etc.}).

This example makes a figure out of a graphic.  @LaTeX{} will place that
graphic and its caption at the top of a page or, if it is pushed to the
end of the document, on a page of floats.

@example
\usepackage@{graphicx@}  % in preamble
  ...
\begin@{figure@}[t]
  \centering
  \includegraphics[width=0.5\textwidth]@{CTANlion.png@}
  \caption@{The CTAN lion, by Duane Bibby@}
\end@{figure@}
@end example


@node filecontents
@section @code{filecontents}: Write an external file

@EnvIndex{filecontents}
@EnvIndex{filecontents*}
@cindex external files, writing
@cindex writing external files

Synopsis:

@example
\begin@{filecontents@}@{@var{filename}@}
  @var{text}
\end@{filecontents@}
@end example

@noindent
or

@example
\begin@{filecontents*@}@{@var{filename}@}
  @var{text}
\end@{filecontents*@}
@end example

Create a file named @var{filename} and fill it with @var{text}.  The
unstarred version of the environment @code{filecontents} prefixes the
content of the created file with a header; see the example below.  The
starred version @code{filecontents*} does not include the header.

This environment can be used anywhere in the preamble, although it often
appears before the @code{\documentclass} command.  It is typically used
when a source file requires a nonstandard style or class file.  The
environment will write that file to the directory containing the source
and thus make the source file self-contained.  Another use is to include
@code{bib} references in the file, again to make it self-contained.

The environment checks whether a file of that name already exists and if
so, does not do anything.  There is a @file{filecontents} package that
redefines the @code{filecontents} environment so that instead of doing
nothing in that case, it will overwrite the existing file.

For example, this document

@example
\documentclass@{article@}
\begin@{filecontents@}@{JH.sty@}
\newcommand@{\myname@}@{Jim Hef@{@}feron@}
\end@{filecontents@}
\usepackage@{JH@}
\begin@{document@}
Article by \myname.
\end@{document@}
@end example

@noindent
produces this file @file{JH.sty}.

@example
%% LaTeX2e file `JH.sty'
%% generated by the `filecontents' environment
%% from source `test' on 2015/10/12.
%%
\newcommand@{\myname@}@{Jim Hef@{@}feron@}
@end example


@node flushleft
@section @code{flushleft}

@EnvIndex{flushleft}
@cindex left-justifying text, environment for
@cindex ragged right text, environment for

Synopsis:

@example
\begin@{flushleft@}
  @var{line1} \\
  @var{line2} \\
  ...
\end@{flushleft@}
@end example

@findex \\ @r{for @code{flushleft}}
An environment that creates a paragraph whose lines are flush to the
left-hand margin, and ragged right. If you have lines that are too long
then @LaTeX{} will linebreak them in a way that avoids hyphenation and
stretching or shrinking spaces.  To force a new line use a double
backslash, @code{\\}.  For the declaration form
see@tie{}@ref{\raggedright}.

This creates a box of text that is at most 3 inches wide, with the text
flush left and ragged right.

@example
\noindent\begin@{minipage@}@{3in@}
\begin@{flushleft@}
  A long sentence that will be broken by \LaTeX@{@}
    at a convenient spot. \\
  And, a fresh line forced by the double backslash.
\end@{flushleft@}
\end@{minipage@}
@end example


@menu
* \raggedright::        Declaration form of the @code{flushleft} environment.
@end menu


@node \raggedright
@subsection @code{\raggedright}

@findex \raggedright
@cindex ragged right text
@cindex left-justifying text
@cindex justification, ragged right

Synopses:

@example
@{\raggedright  ... @}
@end example

@noindent
or

@example
\begin@{@var{environment}@} \raggedright
  ...
\end@{@var{environment}@}
@end example

A declaration which causes lines to be flush to the left margin and
ragged right. It can be used inside an environment such as @code{quote}
or in a @code{parbox}.  For the environment form
see@tie{}@ref{flushleft}.

Unlike the @code{flushleft} environment, the @code{\raggedright}
command does not start a new paragraph; it only changes how @LaTeX{}
formats paragraph units.  To affect a paragraph unit's format, the
scope of the declaration must contain the blank line or @code{\end}
command that ends the paragraph unit.

Here @code{\raggedright} in each second column keeps @LaTeX{} from doing
very awkward typesetting to fit the text into the narrow column.  Note
that @code{\raggedright} is inside the curly braces @code{@{...@}} to
delimit its effect.

@example
\begin@{tabular@}@{rp@{2in@}@}
  Team alpha  &@{\raggedright This team does all the real work.@} \\
  Team beta   &@{\raggedright This team ensures that the water
                cooler is never empty.@}                         \\
\end@{tabular@}
@end example


@node flushright
@section @code{flushright}

@EnvIndex{flushright}
@cindex ragged left text, environment for
@cindex right-justifying text, environment for

@example
\begin@{flushright@}
  @var{line1} \\
  @var{line2} \\
  ...
\end@{flushright@}
@end example

@findex \\ (for @code{flushright})
An environment that creates a paragraph whose lines are flush to the
right-hand margin and ragged left. If you have lines that are too long
to fit the margins then @LaTeX{} will linebreak them in a way that
avoids hyphenation and stretching or shrinking spaces.  To force a new
line use a double backslash, @code{\\}.  For the declaration form
see@tie{}@ref{\raggedleft}.

For an example related to this environment, see@tie{}@ref{flushleft}.

@menu
* \raggedleft::   Declaration form of the @code{flushright} environment.
@end menu


@node \raggedleft
@subsection @code{\raggedleft}

@findex \raggedleft
@cindex ragged left text
@cindex justification, ragged left
@cindex right-justifying text

Synopses:

@example
@{\raggedleft  ... @}
@end example

@noindent
or

@example
\begin@{@var{environment}@} \raggedleft
  ...
\end@{@var{environment}@}
@end example

A declaration which causes lines to be flush to the right margin and
ragged left. It can be used inside an environment such as @code{quote}
or in a @code{parbox}.  For the environment form
see@tie{}@ref{flushright}.

Unlike the @code{flushright} environment, the @code{\raggedleft}
command does not start a new paragraph; it only changes how @LaTeX{}
formats paragraph units.  To affect a paragraph unit's format, the
scope of the declaration must contain the blank line or @code{\end}
command that ends the paragraph unit.

For an example related to this environment, see@tie{}@ref{\raggedright}.


@node itemize
@section @code{itemize}

@EnvIndex{itemize}
@findex \item
@cindex lists of items
@cindex unordered lists
@cindex bulleted lists
@cindex bullet lists

Synopsis:

@example
\begin@{itemize@}
  \item[@var{optional label of first item}] @var{text of first item}
  \item[@var{optional label of second item}] @var{text of second item}
  ...
\end@{itemize@}
@end example

Produce a list that is unordered, sometimes called a bullet list.  The
environment must have at least one @code{\item}; having none causes the
@LaTeX{} error @samp{Something's wrong--perhaps a missing \item}.

This gives a two-item list.

@example
\begin@{itemize@}
 \item Pencil and watercolor sketch by Cassandra
 \item Rice portrait 
\end@{itemize@}
@end example

@noindent
As a top-level list each label would come out as a bullet, @bullet{}.
The format of the labeling depends on the nesting level; see below.

@findex \item
Start list items with the @code{\item} command (@pxref{\item}).  If you
give @code{\item} an optional argument by following it with square
brackets, as in @code{\item[Optional label]}, then by default it will
appear in bold and be flush right, so it could extend into the left
margin.  For labels that are flush left see the @ref{description}
environment. Following the @code{\item} is optional text, which may
contain multiple paragraphs.

@findex \labelitemi
@findex \labelitemii
@findex \labelitemiii
@findex \labelitemiv
@anchor{itemize labelitemi}
@anchor{itemize labelitemii}
@anchor{itemize labelitemiii}
@anchor{itemize labelitemiv}
Itemized lists can be nested within one another, up to four levels deep.
They can also be nested within other paragraph-making environments, such
as @code{enumerate} (@pxref{enumerate}).  The @code{itemize} environment
uses the commands @code{\labelitemi} through @code{\labelitemiv} to
produce the default label (this also uses the convention of lowercase
roman numerals at the end of the command names that signify the nesting
level).  These are the default marks at each level.

@enumerate
@item @bullet{} (bullet, from @code{\textbullet})
@item @b{-@w{-}} (bold en-dash, from @code{\normalfont\bfseries\textendash})
@item * (asterisk, from @code{\textasteriskcentered})
@iftex
@item @math{\cdot} (centered dot, from @code{\textperiodcentered})
@end iftex
@ifnottex
@item . (centered dot, rendered here as a period, from @code{\textperiodcentered})
@end ifnottex
@end enumerate

Change the labels with @code{\renewcommand}.  For instance, this makes
the first level use diamonds.

@example
\renewcommand@{\labelitemi@}@{$\diamond$@}
@end example

@findex \leftmargin
@findex \leftmargini
@findex \leftmarginii
@findex \leftmarginiii
@findex \leftmarginiv
@findex \leftmarginv
@findex \leftmarginvi
@anchor{itemize leftmargin}
@anchor{itemize leftmargini}
@anchor{itemize leftmarginii}
@anchor{itemize leftmarginiii}
@anchor{itemize leftmarginiv}
@anchor{itemize leftmarginv}
@anchor{itemize leftmarginvi}
The distance between the left margin of the enclosing environment and
the left margin of the @code{itemize} list is determined by the
parameters @code{\leftmargini} through @code{\leftmarginvi}.  (Note the
convention of using lowercase roman numerals a the end of the command
name to denote the nesting level.)  The defaults are: @code{2.5em} in
level 1 (@code{2em} in two-column mode), @code{2.2em} in level 2,
@code{1.87em} in level 3, and @code{1.7em} in level 4, with smaller
values for more deeply nested levels.

For other major @LaTeX{} labeled list environments, see
@ref{description} and @ref{enumerate}.  For information about list
layout parameters, including the default values, and for information
about customizing list layout, see @ref{list}.  The package
@file{enumitem} is useful for customizing lists.

This example greatly reduces the margin space for outermost itemized
lists.

@example
\setlength@{\leftmargini@}@{1.25em@} % default 2.5em
@end example

@findex \parskip @r{example}
Especially for lists with short items, it may be desirable to elide
space between items.  Here is an example defining an @code{itemize*}
environment with no extra spacing between items, or between paragraphs
within a single item (@code{\parskip} is not list-specific,
@pxref{\parindent & \parskip}):

@example
\newenvironment@{itemize*@}%
  @{\begin@{itemize@}%
    \setlength@{\itemsep@}@{0pt@}%
    \setlength@{\parsep@}@{0pt@}@}%
    \setlength@{\parskip@}@{0pt@}@}%
  @{\end@{itemize@}@}
@end example


@node letter
@section @code{letter} environment: writing letters

@EnvIndex{letter}

This environment is used for creating letters.  @xref{Letters}.


@node list
@section @code{list}

@EnvIndex{list}
@cindex lists of items, generic

Synopsis:

@example
\begin@{list@}@{@var{labeling}@}@{@var{spacing}@}
  \item[@var{optional label of first item}] @var{text of first item}
  \item[@var{optional label of second item}] @var{text of second item}
  ...
\end@{list@}
@end example

An environment for constructing lists.

Note that this environment does not typically appear in the document
body.  Most lists created by @LaTeX{} authors are the ones that come
standard: the @code{description}, @code{enumerate}, and @code{itemize}
environments (@pxref{description}, @ref{enumerate}, and @ref{itemize}).

Instead, the @code{list} environment is most often used in macros.  For
example, many standard @LaTeX{} environments that do not immediately
appear to be lists are in fact constructed using @code{list}, including
@code{quotation}, @code{quote}, and @code{center} (@pxref{quotation &
quote}, @pxref{center}).

This uses the @code{list} environment to define a new custom
environment.

@example
\newcounter@{namedlistcounter@}  % number the items
\newenvironment@{named@}
  @{\begin@{list@}
     @{Item~\Roman@{namedlistcounter@}.@} % labeling 
     @{\usecounter@{namedlistcounter@}   % set counter
      \setlength@{\leftmargin@}@{3.5em@}@} % set spacing 
  @}
  @{\end@{list@}@}

\begin@{named@}
  \item Shows as ``Item~I.''
  \item[Special label.] Shows as ``Special label.''
  \item Shows as ``Item~II.''
\end@{named@}
@end example

The mandatory first argument @var{labeling} specifies the default
labeling of list items.  It can contain text and @LaTeX{} commands, as
above where it contains both @samp{Item} and @samp{\Roman@{...@}}.
@LaTeX{} forms the label by putting the @var{labeling} argument in a box
of width @code{\labelwidth}.  If the label is wider than that, the
additional material extends to the right.  When making an instance of a
list you can override the default labeling by giving @code{\item} an
optional argument by including square braces and the text, as in the
above @code{\item[Special label.]}; @pxref{\item}.

The mandatory second argument @var{spacing} has a list of commands.
This list can be empty.  A command that can go in here is
@code{\usecounter@{@var{countername}@}} (@pxref{\usecounter}).  Use this
to tell @LaTeX{} to number the items using the given counter.  The
counter will be reset to zero each time @LaTeX{} enters the environment,
and the counter is incremented by one each time @LaTeX{} encounters an
@code{\item} that does not have an optional argument.

@findex \makelabel
@anchor{list makelabel} Another command that can go in @var{spacing} is
@code{\makelabel}, which constructs the label box.  By default it puts
the contents flush right.  Its only argument is the label, which it
typesets in LR mode (@pxref{Modes}). One example of changing its
definition is that to the above @code{named} example, before the
definition of the environment add
@code{\newcommand@{\namedmakelabel@}[1]@{\textsc@{#1@}@}}, and between
the @code{\setlength} command and the parenthesis that closes the
@var{spacing} argument also add @code{\let\makelabel\namedmakelabel}.
Then the items will be typeset in small caps.  Similarly, changing the
second code line to @code{\let\makelabel\fbox} puts the labels inside a
framed box.  Another example of the @code{\makelabel} command is below,
in the definition of the @code{redlabel} environment.

Also often in @var{spacing} are commands to redefine the spacing for the
list.  Below are the spacing parameters with their default values.
(Default values for derived environments such as @code{itemize} can be
different than the values shown here.) See also the figure that follows
the list.  Each is a length (@pxref{Lengths}).  The vertical spaces are
normally rubber lengths, with @code{plus} and @code{minus} components,
to give @TeX{} flexibility in setting the page.  Change each with a
command such as @code{\setlength@{itemsep@}@{2pt plus1pt minus1pt@}}.
For some effects these lengths should be zero or negative.

@ftable @code
@item \itemindent
@anchor{list itemindent}
Extra horizontal space indentation, beyond @code{leftmargin}, of the
first line each item.  Its default value is @code{0pt}.

@item \itemsep
@anchor{list itemsep}
Vertical space between items, beyond the @code{\parsep}.  The defaults
for the first three levels in @LaTeX{}'s @samp{article}, @samp{book},
and @samp{report} classes at 10 point size are: @code{4pt plus2pt
minus1pt}, @code{\parsep} (that is, @code{2pt plus1pt minus1pt}), and
@code{\topsep} (that is, @code{2pt plus1pt minus1pt}).  The defaults at
11 point are: @code{4.5pt plus2pt minus1pt}, @code{\parsep} (that is,
@code{2pt plus1pt minus1pt}), and @code{topsep} (that is, @code{2pt
plus1pt minus1pt}).  The defaults at 12 point are: @code{5pt plus2.5pt
minus1pt}, @code{\parsep} (that is, @code{2.5pt plus1pt minus1pt}), and
@code{\topsep} (that is, @code{2.5pt plus1pt minus1pt}).

@item \labelsep
@anchor{list labelsep}
Horizontal space between the label and text of an item.
The default for @LaTeX{}'s @samp{article}, @samp{book},
and @samp{report} classes is @code{0.5em}.

@item \labelwidth
@anchor{list labelwidth}
Horizontal width.  The box containing the label is nominally this wide.
If @code{\makelabel} returns text that is wider than this then the first
line of the item will be indented to make room for this extra material.
If @code{\makelabel} returns text of width less than or equal to
@code{\labelwidth} then @LaTeX{}'s default is that the label is typeset
flush right in a box of this width.

The left edge of the label box is
@code{\leftmargin}+@code{\itemindent}-@code{\labelsep}-@code{\labelwidth}
from the left margin of the enclosing environment.

The default for @LaTeX{}'s @samp{article}, @samp{book}, and
@samp{report} classes at the top level is
@code{\leftmargini}-@code{\labelsep}, (which is @code{2em} in one column
mode and @code{1.5em} in two column mode).  At the second level it is
@code{\leftmarginii}-@code{\labelsep}, and at the third level it is
@code{\leftmarginiii}-@code{\labelsep}.  These definitions make the
label's left edge coincide with the left margin of the enclosing
environment.

@item \leftmargin
@anchor{list leftmargin}
Horizontal space between the left margin of the enclosing environment
(or the left margin of the page if this is a top-level list), and the
left margin of this list.  It must be non-negative.

In the standard @LaTeX{} document classes, a top-level list has this set
to the value of @code{\leftmargini}, while a list that is nested inside
a top-level list has this margin set to @code{\leftmarginii}.  More
deeply nested lists get the values of @code{\leftmarginiii} through
@code{\leftmarginvi}.  (Nesting greater than level five generates the
error message @samp{Too deeply nested}.)

The defaults for the first three levels in @LaTeX{}'s @samp{article},
@samp{book}, and @samp{report} classes are: @code{\leftmargini} is
@code{2.5em} (in two column mode, @code{2em}), @code{\leftmarginii} is
@code{2.2em}, and @code{\leftmarginiii} is @code{1.87em}.

@item \listparindent
@anchor{list listparindent}
Horizontal space of additional line indentation, beyond
@code{\leftmargin}, for second and subsequent paragraphs within a list
item.  A negative value makes this an ``outdent''.  Its default value
is @code{0pt}.

@item \parsep
@anchor{list parsep}
Vertical space between paragraphs within an item.  In the @samp{book}
and @samp{article} classes The defaults for the first three levels in
@LaTeX{}'s @samp{article}, @samp{book}, and @samp{report} classes at 10
point size are: @code{4pt plus2pt minus1pt}, @code{2pt plus1pt
minus1pt}, and @code{0pt}.  The defaults at 11 point size are:
@code{4.5pt plus2pt minus1pt}, @code{2pt plus1pt minus1pt}, and
@code{0pt}.  The defaults at 12 point size are: @code{5pt plus2.5pt
minus1pt}, @code{2.5pt plus1pt minus1pt}, and @code{0pt}.

@item \partopsep
@anchor{list partopsep}
Vertical space added, beyond @code{\topsep}+@code{\parskip}, to the top
and bottom of the entire environment if the list instance is preceded by
a blank line.  (A blank line in the @LaTeX{} source before the list
changes spacing at both the top and bottom of the list; whether the line
following the list is blank does not matter.)

The defaults for the first three levels in @LaTeX{}'s @samp{article},
@samp{book}, and @samp{report} classes at 10 point size are: @code{2pt
plus1 minus1pt}, @code{2pt plus1pt minus1pt}, and @code{1pt plus0pt
minus1pt}.  The defaults at 11 point are: @code{3pt plus1pt minus1pt},
@code{3pt plus1pt minus1pt}, and @code{1pt plus0pt minus1pt}).  The
defaults at 12 point are: @code{3pt plus2pt minus3pt}, @code{3pt plus2pt
minus2pt}, and @code{1pt plus0pt minus1pt}.

@item \rightmargin
@anchor{list rightmargin}
Horizontal space between the right margin of the list and the right
margin of the enclosing environment.  Its default value is @code{0pt}.
It must be non-negative.

@item \topsep
@anchor{list topsep}
Vertical space added to both the top and bottom of the list, in addition
to @code{\parskip} (@pxref{\parindent & \parskip}).  The defaults for
the first three levels in @LaTeX{}'s @samp{article}, @samp{book}, and
@samp{report} classes at 10 point size are: @code{8pt plus2pt minus4pt},
@code{4pt plus2pt minus1pt}, and @code{2pt plus1pt minus1pt}.  The
defaults at 11 point are: @code{9pt plus3pt minus5pt}, @code{4.5pt
plus2pt minus1pt}, and @code{2pt plus1pt minus1pt}.  The defaults at 12
point are: @code{10pt plus4pt minus6pt}, @code{5pt plus2.5pt minus1pt},
and @code{2.5pt plus1pt minus1pt}.

@end ftable

This shows the horizontal and vertical distances.

@float
@image{latex2e-figures/list,3.21in,,,.png}
@end float

The lengths shown are listed below.  The key relationship is that the
right edge of the bracket for @var{h1} equals the right edge of the
bracket for @var{h4}, so that the left edge of the label box is at
@var{h3}+@var{h4}-(@var{h0}+@var{h1}).

@table @var
@item v0
@math{@code{@\topsep} + @code{@\parskip}} if
the list environment does not start a new paragraph, and
@code{\topsep}+@code{\parskip}+@code{\partopsep} if it does

@item v1
@code{\parsep}

@item v2
@code{\itemsep}+@code{\parsep}

@item v3
Same as @var{v0}.  (This space is affected by whether a blank line
appears in the source above the environment; whether a blank line
appears in the source below the environment does not matter.)

@item h0
@code{\labelwidth}

@item h1
@code{\labelsep}

@item h2
@code{\listparindent}

@item h3
@code{\leftmargin}

@item h4
@code{\itemindent}

@item h5
@code{\rightmargin}

@end table

The list's left and right margins, shown above as @var{h3} and @var{h5},
are with respect to the ones provided by the surrounding environment, or
with respect to the page margins for a top-level list.  The line width
used for typesetting the list items is @code{\linewidth} (@pxref{Page
layout parameters}).  For instance, set the list's left margin to be one
quarter of the distance between the left and right margins of the
enclosing environment with
@code{\setlength@{\leftmargin@}@{0.25\linewidth@}}.

Page breaking in a list structure is controlled by the three
parameters below. For each, the @LaTeX{} default is
@code{-\@@lowpenalty}, that is, @code{-51}.  Because it is negative,
it somewhat encourages a page break at each spot.  Change it with,
e.g., @code{\@@beginparpenalty=9999}; a value of 10000 prohibits a
page break.

@ftable @code
@item \@@beginparpenalty
@anchor{list beginparpenalty}
The page breaking penalty for breaking before the list (default @code{-51}).

@item \@@itempenalty
@anchor{list itempenalty}
The page breaking penalty for breaking before a list item (default @code{-51}).

@item \@@endparpenalty
@anchor{list endparpenalty}
The page breaking penalty for breaking after a list (default @code{-51}).

@end ftable

@PkgIndex{enumitem}
The package @code{enumitem} is useful for customizing lists.

This example has the labels in red.  They are numbered, and the left
edge of the label lines up with the left edge of the item text.
@xref{\usecounter}.

@example
\usepackage@{color@}
\newcounter@{cnt@}  
\newcommand@{\makeredlabel@}[1]@{\textcolor@{red@}@{#1.@}@}
\newenvironment@{redlabel@}
  @{\begin@{list@}
    @{\arabic@{cnt@}@}
    @{\usecounter@{cnt@}
     \setlength@{\labelwidth@}@{0em@}
     \setlength@{\labelsep@}@{0.5em@}
     \setlength@{\leftmargin@}@{1.5em@}
     \setlength@{\itemindent@}@{0.5em@} % equals \labelwidth+\labelsep
     \let\makelabel=\makeredlabel
    @}
  @}
@{\end@{list@} @}
@end example

@menu
* \item::          An entry in a list.
* trivlist::       A restricted form of @code{list}.
@end menu


@node \item
@subsection @code{\item}: An entry in a list

Synopsis:

@example
\item text of item
@end example

@noindent
or

@example
\item[@var{optional-label}] text of item
@end example

An entry in a list.  The entries are prefixed by a label, whose default
depends on the list type.

Because the optional label is surrounded by square brackets
@samp{[...]}, if you have an item whose text starts with @samp{[}, you
have to hide the bracket inside curly braces, as in: @code{\item
@{[@} is an open square bracket}; otherwise, @LaTeX{} will think it
marks the start of an optional label.

Similarly, if the item does have the optional label and you need a
close square bracket inside that label, you must hide it in the same
way: @code{\item[Close square bracket, @{]@}]}.  @xref{@LaTeX{}
command syntax}.

In this example the enumerate list has two items that use the default
label and one that uses the optional label.

@example
\begin@{enumerate@}
  \item Moe
  \item[sometimes] Shemp
  \item Larry
\end@{enumerate@}
@end example

The first item is labelled @samp{1.}, the second item is labelled
@samp{sometimes}, and the third item is labelled @samp{2.}.  Because
of the optional label in the second item, the third item is not
labelled@tie{}@samp{3.}.
   

@node trivlist
@subsection @code{trivlist}: A restricted form of @code{list}

Synopsis:

@example
\begin@{trivlist@}
  ...
\end@{trivlist@}
@end example

A restricted version of the list environment, in which margins are not
indented and an @code{\item} without an optional argument produces no
text.  It is most often used in macros, to define an environment where
the @code{\item} command as part of the environment's definition.  For
instance, the @code{center} environment is defined essentially like
this:

@example
\newenvironment@{center@}
  @{\begin@{trivlist@}\centering\item\relax@}
  @{\end@{trivlist@}@}
@end example

Using @code{trivlist} in this way allows the macro to inherit some
common code: combining vertical space of two adjacent environments;
detecting whether the text following the environment should be
considered a new paragraph or a continuation of the previous one;
adjusting the left and right margins for possible nested list
environments.

Specifically, @code{trivlist} uses the current values of the list
parameters (@pxref{list}), except that @code{\parsep} is set to the
value of @code{\parskip}, and @code{\leftmargin}, @code{\labelwidth},
and @code{\itemindent} are set to zero.

This example outputs the items as two paragraphs, except that (by
default) they have no paragraph indent and are vertically separated.

@example
\begin@{trivlist@}
\item The \textit@{Surprise@} is not old; no one would call her old.
\item She has a bluff bow, lovely lines.
\end@{trivlist@}
@end example


@node math
@section @code{math}

@EnvIndex{math}
@cindex in-line formulas

Synopsis:

@example
\begin@{math@}
@var{math}
\end@{math@}
@end example

The @code{math} environment inserts given @var{math} material within
the running text.  @code{\(...\)} and @code{$...$} are synonyms.
@xref{Math formulas}.


@node minipage
@section @code{minipage}

@EnvIndex{minipage}
@cindex minipage, creating a

Synopses:

@example
\begin@{minipage@}@{@var{width}@}
  @var{contents}
\end@{minipage@}
@end example

@noindent
or

@example
\begin@{minipage@}[@var{position}][@var{height}][@var{inner-pos}]@{@var{width}@}
  @var{contents}
\end@{minipage@}
@end example

Put @var{contents} into a box that is @var{width} wide.  This is like a
small version of a page; it can contain its own footnotes, itemized
lists, etc. (There are some restrictions, including that it cannot have
floats.)  This box will not be broken across pages.  So @code{minipage}
is similar to @code{\parbox} (@pxref{\parbox}) but here you can have
paragraphs.

This example will be 3@tie{}inches wide, and has two paragraphs.

@example
\begin@{minipage@}@{3in@}
  Stephen Kleene was a founder of the Theory of Computation.

  He was a student of Church, wrote three influential texts,
  was President of the Association for Symbolic Logic,
  and won the National Medal of Science.
\end@{minipage@}
@end example

@noindent
See below for a discussion of the paragraph indent inside a
@code{minipage}.

The required argument @var{width} is a rigid length (@pxref{Lengths}).
It gives the width of the box into which @var{contents} are typeset.

There are three optional arguments, @var{position}, @var{height}, and
@var{inner-pos}.  You need not include all three. For example, get the
default @var{position} and set the @var{height} with
@code{\begin@{minipage@}[c][2.54cm] @var{contents} \end@{minipage@}}.
(Get the natural height with an empty argument, @code{[]}.)

The optional argument @var{position} governs how the @code{minipage}
vertically aligns with the surrounding material.

@table @code
@item c
(synonym @code{m}) Default.  Positions the @code{minipage} so its
vertical center lines up with the center of the adjacent text line (what
Plain @TeX{} calls @code{\vcenter}).

@item t
Match the top line in the @code{minipage} with the baseline of the
surrounding text (Plain @TeX{}'s @code{\vtop}.

@item b
Match the bottom line in the @code{minipage} with the baseline of the
surrounding text (Plain @TeX{}'s @code{\vbox}.
@end table

To see the effects of these, contrast running this

@example
---\begin@{minipage@}[c]@{0.25in@}
  first\\ second\\ third
\end@{minipage@}
@end example

@noindent
with the results of changing @code{c} to @code{b} or@tie{}@code{t}.

The optional argument @var{height} is a rigid length (@pxref{Lengths}).
It sets the height of the @code{minipage}.  You can enter any value
larger than, or equal to, or smaller than the @code{minipage}'s natural
height and @LaTeX{} will not give an error or warning.  You can also set
it to a height of zero or a negative value.

The final optional argument @var{inner-pos} controls the placement of
@var{content} inside the box. These are the possible values are (the
default is the value of @var{position}).

@table @code
@item t
Place @var{content} at the top of the box.

@item c
Place it in the vertical center.

@item b
Place it at the box bottom.

@item s
Stretch @var{contents} out vertically; it must contain vertically
stretchable space.

@end table

The @var{inner-pos} argument makes sense when the @var{height} option
is set to a value larger than the @code{minipage}'s natural height.  To
see the effect of the options, run this example with the various choices
in place of @code{b}.

@example
Text before
\begin@{center@}
  ---\begin@{minipage@}[c][3in][b]@{0.25\textwidth@}
       first\\ second\\ third
  \end@{minipage@}              
\end@{center@}
Text after  
@end example

@cindex indentation of paragraphs, in minipage
@cindex paragraph indentation, in minipage
@findex \parindent
By default paragraphs are not indented in a @code{minipage}.  Change
that with a command such as @code{\setlength@{\parindent@}@{1pc@}} at
the start of @var{contents}.

@cindex footnotes in figures
@cindex figures, footnotes in
Footnotes in a @code{minipage} environment are handled in a way that is
particularly useful for putting footnotes in figures or tables.  A
@code{\footnote} or @code{\footnotetext} command puts the footnote at
the bottom of the minipage instead of at the bottom of the page, and it
uses the @code{\mpfootnote} counter instead of the ordinary
@code{footnote} counter (@pxref{Counters}).

This puts the footnote at the bottom of the table, not the bottom of the
page.

@example
\begin@{center@}           % center the minipage on the line
\begin@{minipage@}@{2.5in@}
  \begin@{center@}         % center the table inside the minipage
    \begin@{tabular@}@{ll@}
      \textsc@{Monarch@}  &\textsc@{Reign@}             \\ \hline
      Elizabeth II      &63 years\footnote@{to date@} \\
      Victoria          &63 years                   \\
      George III        &59 years
    \end@{tabular@}
  \end@{center@}  
\end@{minipage@}
\end@{center@}
@end example

If you nest minipages then there is an oddness when using footnotes.
Footnotes appear at the bottom of the text ended by the next
@code{\end@{minipage@}} which may not be their logical place.

This puts a table containing data side by side with a map graphic.  They
are vertically centered.

@example
\newcommand*@{\vcenteredhbox@}[1]@{\begin@{tabular@}@{@@@{@}c@@@{@}@}#1\end@{tabular@}@}
  ...
\begin@{center@}
  \vcenteredhbox@{\includegraphics[width=0.3\textwidth]@{nyc.png@}@}
  \hspace@{0.1\textwidth@}
  \begin@{minipage@}@{0.5\textwidth@}
    \begin@{tabular@}@{r|l@}
      \multicolumn@{1@}@{r@}@{Borough@} &Pop (million)  \\ \hline
      The Bronx      &$1.5$  \\
      Brooklyn       &$2.6$  \\
      Manhattan      &$1.6$  \\
      Queens         &$2.3$  \\
      Staten Island  &$0.5$  
    \end@{tabular@}
  \end@{minipage@}              
\end@{center@}
@end example


@node picture
@section @code{picture}

@EnvIndex{picture}
@cindex creating pictures
@cindex pictures, creating

Synopses: 
@example
\begin@{picture@}(@var{width},@var{height})
   @var{picture commands} 
\end@{picture@}
@end example

@noindent
or

@example
\begin@{picture@}(@var{width},@var{height})(@var{xoffset},@var{yoffset})
  @var{picture commands}
\end@{picture@}
@end example

An environment to create simple pictures containing lines, arrows,
boxes, circles, and text.  Note that while this environment is not
obsolete, new documents typically use much more powerful graphics
creation systems, such as @code{TikZ}, @code{PSTricks}, @code{MetaPost},
or @code{Asymptote}.  These are not covered in this document; see CTAN.

This shows the parallelogram law for adding vectors.

@findex \unitlength
@example
\setlength@{\unitlength@}@{1cm@}
\begin@{picture@}(6,6)      % picture box will be 6cm wide by 6cm tall
  \put(0,0)@{\vector(2,1)@{4@}@}  % for every 2 over this vector goes 1 up
    \put(2,1)@{\makebox(0,0)[l]@{\ first leg@}@}
  \put(4,2)@{\vector(1,2)@{2@}@}
    \put(5,4)@{\makebox(0,0)[l]@{\ second leg@}@}  
  \put(0,0)@{\line(1,1)@{6@}@}
    \put(3,3)@{\makebox(0,0)[r]@{sum\ @}@}  
\end@{picture@}
@end example

You can also use this environment to place arbitrary material at an
exact location.

@example
\usepackage@{color,graphicx@}  % in preamble
  ...
\begin@{center@}
\setlength@{\unitlength@}@{\textwidth@} 
\begin@{picture@}(1,1)      % leave space, \textwidth wide and tall
  \put(0,0)@{\includegraphics[width=\textwidth]@{desertedisland.jpg@}@}
  \put(0.25,0.35)@{\textcolor@{red@}@{X Treasure here@}@}
\end@{picture@}
\end@{center@}
@end example

@noindent
The red@tie{}X will be precisely a quarter of the @code{\linewidth} from
the left margin, and @code{0.35\linewidth} up from the bottom.  Another
example of this usage is to put similar code in the page header to get
repeat material on each of a document's pages.

The @code{picture} environment has one required argument, a pair of
numbers (@var{width},@var{height}).  Multiply these by the value
@code{\unitlength} to get the nominal size of the output, the space that
@LaTeX{} reserves on the output page.  This nominal size need not be how
large the picture really is; @LaTeX{} will draw things from the picture
outside the picture's box.

This environment also has an optional argument
(@var{xoffset},@var{yoffset}).  It is used to shift the origin.  Unlike
most optional arguments, this one is not contained in square brackets.
As with the required argument, it consists of two real numbers.
Multiply these by @code{\unitlength} to get the point at the lower-left
corner of the picture.

For example, if @code{\unitlength} has been set to @code{1mm}, the
command

@example
\begin@{picture@}(100,200)(10,20)
@end example

@noindent
produces a box of width 100 millimeters and height 200 millimeters.  The
picture's origin is the point (10mm,20mm) and so the lower-left corner
is there, and the upper-right corner is at (110mm,220mm).  When you
first draw a picture you typically omit the optional argument, leaving
the origin at the lower-left corner.  If you then want to modify your
picture by shifting everything, you can just add the appropriate
optional argument.

@cindex position, in picture
Each @var{picture command} tells @LaTeX{} where to put something by
naming its position.  A @dfn{position} is a pair such as @code{(2.4,-5)}
giving the x- and y-coordinates.  A @dfn{coordinate} is a not a length,
it is a real number (it may have a decimal point or a minus sign).  It
specifies a length in multiples of the unit length @code{\unitlength},
so if @code{\unitlength} has been set to @code{1cm}, then the coordinate
2.54 specifies a length of 2.54 centimeters.

@LaTeX{}'s default for @code{\unitlength} is @code{1pt}.  it is a rigid
length (@pxref{Lengths}).  Change it with the @code{\setlength} command
(@pxref{\setlength}).  Make this change only outside of a @code{picture}
environment.

Coordinates are given with respect to an origin, which is normally at
the lower-left corner of the picture.  Note that when a position appears
as an argument, as with @code{\put(1,2)@{...@}}, it is not enclosed in
braces since the parentheses serve to delimit the argument.  Also,
unlike in some computer graphics systems, larger y-coordinates are
further up the page.

There are four ways to put things in a picture: @code{\put},
@code{\multiput}, @code{\qbezier}, and @code{\graphpaper}.  The most
often used is @code{\put}. This

@example
\put(11.3,-0.3)@{...@}
@end example

@noindent
places the object with its reference point at coordinates
@math{(11.3,-0.3)}.  The reference points for various objects will be
described below.
@findex LR box
The @code{\put} command creates an @dfn{LR box} (@pxref{Modes}).
Anything that can go in an @code{\mbox} (@pxref{\mbox & \makebox}) can
go in the text argument of the @code{\put} command.  The reference point
will be the lower left corner of the box.  In this picture

@example
\setlength@{\unitlength@}@{1cm@}
...\begin@{picture@}(1,1)
  \put(0,0)@{\line(1,0)@{1@}@}
  \put(0,0)@{\line(1,1)@{1@}@}
\end@{picture@}
@end example

@noindent
the three dots are just slightly left of the point of the angle formed
by the two lines.  (Also, @code{\line(1,1)@{1@}} does not call for a
line of length one; rather the line has a change in the x coordinate of
1.)

The @code{\multiput}, @code{qbezier}, and @code{graphpaper} commands are
described below.

This draws a rectangle with a wavy top, using @code{\qbezier} for
that curve.

@example
\begin@{picture@}(3,1.5)
  \put(0,0)@{\vector(1,0)@{8@}@}  % x axis
  \put(0,0)@{\vector(0,1)@{4@}@}  % y axis
  \put(2,0)@{\line(0,1)@{3@}@}       % left side rectangle
  \put(4,0)@{\line(0,1)@{3.5@}@}     % right side
  \qbezier(2,3)(2.5,2.9)(3,3.25)
    \qbezier(3,3.25)(3.5,3.6)(4,3.5)
  \thicklines                 % below here, lines are twice as thick
  \put(2,3)@{\line(4,1)@{2@}@}
  \put(4.5,2.5)@{\framebox@{Trapezoidal Rule@}@}
\end@{picture@}
@end example

@menu
* \put::                Place an object at a specified place.
* \multiput::           Draw multiple instances of an object.
* \qbezier::            Draw a quadratic Bezier curve.
* \graphpaper::         Draw graph paper.
* \line::               Draw a straight line.
* \linethickness::      Set thickness of horizontal and vertical lines.
* \thinlines::          The default line thickness.
* \thicklines::         A heavier line thickness.
* \circle::             Draw a circle.
* \oval::               Draw an oval.
* \shortstack::         Make a stack of objects.
* \vector::             Draw a line with an arrow.
* \makebox (picture)::  Draw a box of the specified size.
* \framebox (picture):: Draw a box with a frame around it.
* \frame::              Draw a frame around an object.
* \dashbox::            Draw a dashed box.
@end menu


@node \put
@subsection @code{\put}

@findex \put

Synopsis:

@example
\put(@var{xcoord},@var{ycoord})@{@var{content}@}
@end example

Place @var{content} at the coordinate (@var{xcoord},@var{ycoord}).  See
the discussion of coordinates and @code{\unitlength} in @ref{picture}.
The @var{content} is processed in LR mode (@pxref{Modes}) so it cannot
contain line breaks.

This includes the text into the @code{picture}.

@example
\put(4.5,2.5)@{Apply the \textit@{unpoke@} move@}
@end example

The reference point, the location (4.5,2.5), is the lower left of the
text, at the bottom left of the @samp{A}.


@node \multiput
@subsection @code{\multiput}

@findex \multiput

Synopsis:

@example
\multiput(@var{x},@var{y})(@var{delta_x},@var{delta_y})@{@var{num-copies}@}@{@var{obj}@}
@end example

Copy @var{obj} a total of @var{num-copies} times, with an increment of
@var{delta_x,delta_y}.  The @var{obj} first appears at position
@math{(x,y)}, then at @math{(x+\delta_x,y+\delta_y)}, and so on.

This draws a simple grid with every fifth line in bold (see also
@ref{\graphpaper}).

@example
\begin@{picture@}(10,10)
  \linethickness@{0.05mm@}
  \multiput(0,0)(1,0)@{10@}@{\line(0,1)@{10@}@} 
  \multiput(0,0)(0,1)@{10@}@{\line(1,0)@{10@}@}
  \linethickness@{0.5mm@}
  \multiput(0,0)(5,0)@{3@}@{\line(0,1)@{10@}@}
  \multiput(0,0)(0,5)@{3@}@{\line(1,0)@{10@}@}
\end@{picture@}
@end example


@node \qbezier
@subsection @code{\qbezier}

@findex \qbezier

Synopsis:

@example
\qbezier(@var{x1},@var{y1})(@var{x2},@var{y2})(@var{x3},@var{y3})
\qbezier[@var{num}](@var{x1},@var{y1})(@var{x2},@var{y2})(@var{x3},@var{y3})
@end example

Draw a quadratic Bezier curve whose control points are given by the
three required arguments @code{(@var{x1},@var{y1})},
@code{(@var{x2},@var{y2})}, and @code{(@var{x3},@var{y3})}.  That is,
the curve runs from @var{(x1,y1)} to @var{(x3,y3)}, is quadratic, and is
such that the tangent line at @var{(x1,y1)} passes through
@var{(x2,y2)}, as does the tangent line at @var{(x3,y3)}.

This draws a curve from the coordinate (1,1) to (1,0).

@example
\qbezier(1,1)(1.25,0.75)(1,0)  
@end example

@noindent
The curve's tangent line at (1,1) contains (1.25,0.75), as does the
curve's tangent line at (1,0).

The optional argument @var{num} gives the number of calculated
intermediate points.  The default is to draw a smooth curve whose
maximum number of points is @code{\qbeziermax} (change this value with
@code{\renewcommand}).


@node \graphpaper
@subsection @code{\graphpaper}

@findex \graphpaper
Synopsis:

@example
\graphpaper(@var{x_init},@var{y_init})(@var{x_dimen},@var{y_dimen})
\graphpaper[@var{spacing}](@var{x_init},@var{y_init})(@var{x_dimen},@var{y_dimen})
@end example

Draw a coordinate grid.  Requires the @code{graphpap} package.
The grid's origin is @code{(@var{x_init},@var{y_init})}.
Grid lines come every @var{spacing} units (the default is 10).
The grid extends @var{x_dimen} units to the right and @var{y_dimen} units up.
All arguments must be positive integers.

This make a grid with seven vertical lines and eleven horizontal lines.

@example
\usepackage@{graphpap@}    % in preamble
  ...
\begin@{picture@}(6,20)    % in document body
  \graphpaper[2](0,0)(12,20)
\end@{picture@}
@end example

@noindent
The lines are numbered every ten units.


@node \line
@subsection @code{\line}

@findex \line

Synopsis:

@example
\line(@var{x_run},@var{y_rise})@{@var{travel}@}
@end example

Draw a line.  It slopes such that it vertically rises @var{y_rise} for
every horizontal @var{x_run}.  The @var{travel} is the total horizontal
change@tie{}--- it is not the length of the vector, it is the change in
@math{x}.  In the special case of vertical lines, where
(@var{x_run},@var{y_rise})=(0,1), the @var{travel} gives the change in
@math{y}.

This draws a line starting at coordinates (1,3).

@example
\put(1,3)@{\line(2,5)@{4@}@}
@end example

@noindent
For every over 2, this line will go up 5.  Because @var{travel}
specifies that this goes over 4, it must go up@tie{}10.  Thus its
endpoint is @math{(1,3)+(4,10)=(5,13)}.  In particular, note that
@math{@var{travel}=4} is not the length of the line, it is the change in
@math{x}.

The arguments @var{x_run} and @var{y_rise} are integers that can be
positive, negative, or zero. (If both are 0 then @LaTeX{} treats the
second as 1.)  With
@code{\put(@var{x_init},@var{y_init})@{\line(@var{x_run},@var{y_rise})@{@var{travel}@}@}},
if @var{x_run} is negative then the line's ending point has a first
coordinate that is less than @var{x_init}.  If @var{y_rise} is negative
then the line's ending point has a second coordinate that is less than
@var{y_init}.

If @var{travel} is negative then you get @code{LaTeX Error: Bad \line or
\vector argument.}

@cindex @code{pict2e} package
@cindex graphics packages
@PkgIndex{pict2e}
@PkgIndex{TikZ}
@PkgIndex{PSTricks}
@PkgIndex{MetaPost}
@PkgIndex{Asymptote}
Standard @LaTeX{} can only draw lines with a limited range of slopes
because these lines are made by putting together line segments from
pre-made fonts.  The two numbers @var{x_run} and @var{y_rise} must have
integer values from @minus{}6 through@tie{}6.  Also, they must be
relatively prime, so that @var{(x_run,y_rise)} can be (2,1) but not
(4,2) (if you choose the latter then instead of lines you get sequences
of arrowheads; the solution is to switch to the former).  To get lines
of arbitrary slope and plenty of other shapes in a system like
@code{picture}, see the package @file{pict2e} on CTAN.  Another solution
is to use a full-featured graphics system such as @file{TikZ}, or
@file{PSTricks}, or @file{MetaPost}, or @file{Asymptote}


@node \linethickness
@subsection @code{\linethickness}

@findex \linethickness

Synopsis:

@example
\linethickness@{@var{dim}@}
@end example

Declares the thickness of subsequent horizontal and vertical lines in a
picture to be @var{dim}, which must be a positive length
(@pxref{Lengths}).  It differs from @code{\thinlines} and
@code{\thicklines} in that it does not affect the thickness of slanted
lines, circles, or ovals.


@node \thinlines
@subsection @code{\thinlines}

@findex \thinlines

Declaration to set the thickness of subsequent lines, circles, and ovals
in a picture environment to be 0.4@dmn{pt}.  This is the default
thickness, so this command is unnecessary unless the thickness has been
changed with either @ref{\linethickness} or @ref{\thicklines}.


@node \thicklines
@subsection @code{\thicklines}

@findex \thicklines

Declaration to set the thickness of subsequent lines, circles, and ovals
in a picture environment to be 0.8@dmn{pt}.  See also
@ref{\linethickness} and @ref{\thinlines}.  This command is illustrated
in the Trapezoidal Rule example of @ref{picture}.


@node \circle
@subsection @code{\circle}

@findex \circle

Synopsis:

@example
\circle@{@var{diameter}@}
\circle*@{@var{diameter}@}
@end example

Produces a circle with a diameter as close as possible to the specified
one.  The @code{*}@tie{}form produces a filled-in circle.

This draws a circle of radius 6, centered at @code{(5,7)}.

@example
\put(5,7)@{\circle@{6@}@}
@end example

The available radii for @code{circle} are, in points, the even
numbers from 2 to 20, inclusive.  For @code{circle*} they are all the
integers from 1 to 15.


@node \oval
@subsection @code{\oval}

@findex \oval

Synopsis:

@example
\oval(@var{width},@var{height})
\oval(@var{width},@var{height})[@var{portion}]
@end example

Produce a rectangle with rounded corners.  The optional argument
@var{portion} allows you to produce only half or a quarter of the oval.
For half an oval take @var{portion} to be one of these.

@table @code
@item t
top half
@item b
bottom half
@item r
right half
@item l
left half
@end table

Produce only one quarter of the oval by setting @var{portion} to
@code{tr}, @code{br}, @code{bl}, or @code{tl}.

This draws the top half of an oval that is 3 wide and 7 tall.  

@example
\put(5,7)@{\oval(3,7)[t]@}
@end example

@noindent
The (5,7) is the center of the entire oval, not just the center of the
top half.

These shapes are not ellipses.  They are rectangles whose corners are
made with quarter circles.  These circles have a maximum radius of
20@dmn{pt} (@pxref{\circle} for the sizes).  Thus large ovals are just
boxes with a small amount of corner rounding.


@node \shortstack
@subsection @code{\shortstack}

@findex \shortstack

Synopsis:

@example
\shortstack[@var{position}]@{@var{line 1} \\ ... @}
@end example

Produce a vertical stack of objects.

This labels the @math{y} axis.

@example
\put(0,0)@{\vector(1,0)@{4@}@}   % x axis
\put(0,0)@{\vector(0,1)@{2@}@}   % y
\put(-0.25,2)@{\makebox[0][r]@{\shortstack[r]@{$y$\\ axis@}@}@}
@end example

@noindent
For a short stack, the reference point is the lower left of the stack.
In the above example the @ref{\mbox & \makebox} puts the stack flush
right in a zero width box so in total the short stack sits slightly to
the left of the @math{y}@tie{}axis.

The valid positions are:

@table @code
@item r
Make objects flush right
@item l
Make objects flush left
@item c
Center objects (default)
@end table

@findex \\ @r{(for @code{\shortstack} objects)}
Separate objects into lines with @code{\\}.  These stacks are short in
that, unlike in a @code{tabular} or @code{array} environment, here the
rows are not spaced out to be of even heights.  Thus, in
@code{\shortstack@{X\\o\\o\\X@}} the first and last rows are taller than
the middle two.  You can adjust row heights either by putting in the
usual interline spacing with @code{\shortstack@{X\\ \strut o\\o\\X@}},
or by hand, via an explicit zero-width box @code{\shortstack@{X \\
\rule@{0pt@}@{12pt@} o\\o\\X@}} or by using @code{\\}'s optional
argument @code{\shortstack@{X\\[2pt] o\\o\\X@}}.

The @code{\shortstack} command is also available outside the
@code{picture} environment.


@node \vector
@subsection @code{\vector}

@findex \vector

Synopsis:

@example
\vector(@var{x_run},@var{y_rise})@{@var{travel}@}
@end example

Draw a line ending in an arrow.  The slope of that line is: it
vertically rises @var{y_rise} for every horizontal @var{x_run}.  The
@var{travel} is the total horizontal change@tie{}--- it is not the
length of the vector, it is the change in @math{x}.  In the special case
of vertical vectors, if (@var{x_run},@var{y_rise})=(0,1), then
@var{travel} gives the change in @math{y}.

For an example see @ref{picture}.

For elaboration on @var{x_run} and @var{y_rise} see @ref{\line}.  As
there, the values of @var{x_run} and @var{y_rise} are limited.  For
@code{\vector} you must chooses integers between @minus{}4 and 4,
inclusive.  Also, the two you choose must be relatively prime.  Thus,
@code{\vector(2,1)@{4@}} is acceptable but @code{\vector(4,2)@{4@}} is
not (if you use the latter then you get a sequence of arrowheads).


@node \makebox (picture)
@subsection @code{\makebox} (picture)

@findex \makebox @r{(for @code{picture})}

Synopsis:

@example
\makebox(@var{rec-width},@var{rec-height})@{@var{text}@}
\makebox(@var{rec-width},@var{rec-height})[@var{position}]@{@var{text}@}
@end example

Make a box to hold @var{text}.  This command fits with the
@code{picture} environment, although you can use it outside of there,
because @var{rec-width} and @var{rec-height} are numbers specifying
distances in terms of the @code{\unitlength} (@pxref{picture}).  This
command is similar to the normal @code{\makebox} command (@pxref{\mbox &
\makebox}) except here that you must specify the width and height.  This
command is fragile (@pxref{\protect}).

This makes a box of length 3.5 times @code{\unitlength} and height 4
times @code{\unitlength}.

@example
\put(1,2)@{\makebox(3.5,4)@{...@}@}
@end example

The optional argument @code{@var{position}} specifies where in the box
the @var{text} appears.  The default is to center it, both horizontally
and vertically.  To place it somewhere else, use a string with one or
two of these letters.

@table @code
@item t
Puts @var{text} the top of the box.

@item b
Put @var{text} at the bottom.

@item l
Put @var{text} on the left.

@item r
Put @var{text} on the right.

@end table


@node \framebox (picture)
@subsection @code{\framebox} (picture)

@findex \framebox

Synopsis:

@example
\framebox(@var{rec-width},@var{rec-height})@{@var{text}@}
\framebox(@var{rec-width},@var{rec-height})[@var{position}]@{@var{text}@}
@end example

This is the same as @ref{\makebox (picture)} except that it puts a frame
around the outside of the box that it creates.  The reference point is
the bottom left corner of the frame.  This command fits with the
@code{picture} environment, although you can use it outside of there,
because lengths are numbers specifying the distance in terms of the
@code{\unitlength} (@pxref{picture}).  This command is fragile
(@pxref{\protect}).

This example creates a frame 2.5@tie{}inches by 3@tie{}inches and puts
the text in the center.

@example
\setlength@{\unitlength@}@{1in@}
\framebox(2.5,3)@{test text@}
@end example

The required arguments are that the rectangle has overall width
@var{rect-width} units and height @var{rect-height} units.

The optional argument @var{position} specifies the position of
@var{text}; see @ref{\makebox (picture)} for the values that it can
take.

@findex \fboxrule
@findex \fboxsep
The rule has thickness @code{\fboxrule} and there is a blank space
@code{\fboxsep} between the frame and the contents of the box.

For this command, you must specify the @var{width} and @var{height}.  If
you want to just put a frame around some contents whose dimension is
determined in some other way then either use @code{\fbox} (@pxref{\fbox
& \framebox}) or @code{\frame} (@pxref{\frame}).


@node \frame
@subsection @code{\frame}

@findex \frame

Synopsis:

@example
\frame@{@var{contents}@}
@end example

Puts a rectangular frame around @var{contents}.  The reference point is
the bottom left corner of the frame.  In contrast to @code{\framebox}
(@pxref{\framebox (picture)}), this command puts no extra space is put
between the frame and the object.  It is fragile (@pxref{\protect}).


@node \dashbox
@subsection @code{\dashbox}

@findex \dashbox

Synopsis:

@example
\dashbox@{@var{dash-len}@}(@var{rect-width},@var{rect-height})@{@var{text}@}
\dashbox@{@var{dash-len}@}(@var{rect-width},@var{rect-height})[@var{position}]@{@var{text}@}
@end example

Create a dashed rectangle around @var{text}.  This command fits with the
@code{picture} environment, although you can use it outside of there,
because lengths are numbers specifying the distance in terms of the
@code{\unitlength} (@pxref{picture}).

The required arguments are: dashes are @var{dash-len} units long, with
the same length gap, and the rectangle has overall width
@var{rect-width} units and height @var{rect-height} units.

The optional argument @var{position} specifies the position of
@var{text}; see @ref{\makebox (picture)} for the values that it can
take.

This shows that you can use non-integer value for @var{dash-len}.

@example
\put(0,0)@{\dashbox@{0.1@}(5,0.5)@{My hovercraft is full of eels.@}@}
@end example

@noindent
Each dash will be @code{0.1\unitlength} long, the box's width is
@code{5\unitlength} and its height is @code{0.5\unitlength}.

As in that example, a dashed box looks best when @var{rect-width} and
@var{rect-height} are multiples of the @var{dash-len}.


@node quotation & quote
@section @code{quotation} & @code{quote}

@EnvIndex{quotation}
@cindex quoted text with paragraph indentation, displaying
@cindex displaying quoted text with paragraph indentation
@cindex paragraph indentations in quoted text
@EnvIndex{quote}
@cindex quoted text without paragraph indentation, displaying
@cindex displaying quoted text without paragraph indentation
@cindex paragraph indentations in quoted text, omitting

Synopsis:

@example
\begin@{quotation@}
  @var{text}
\end@{quotation@}
@end example

@noindent
or 

@example
\begin@{quote@}
  @var{text}
\end@{quote@}
@end example

Include a quotation. Both environments indent margins on both sides by
@code{\leftmargin} and the text is right-justified.

They differ in how they treat paragraphs. In the @code{quotation}
environment, paragraphs are indented by 1.5@dmn{em} and the space
between paragraphs is small, @code{0pt plus 1pt}.  In the @code{quote}
environment, paragraphs are not indented and there is vertical space
between paragraphs (it is the rubber length @code{\parsep}).

@example
\begin@{quotation@} \small\it
  Four score and seven years ago
  ... shall not perish from the earth.
  \hspace@{1em plus 1fill@}---Abraham Lincoln
\end@{quotation@}
@end example


@node tabbing
@section @code{tabbing}

@EnvIndex{tabbing}
@cindex tab stops, using
@cindex lining text up using tab stops
@cindex alignment via tabbing

Synopsis:

@example
\begin@{tabbing@}
@var{row1col1} \= @var{row1col2} ...  \\
@var{row2col1} \> @var{row2col2} ...  \\
...
\end@{tabbing@}
@end example

Align text in columns, by setting tab stops and tabbing to them much as
was done on a typewriter.  This is less often used than the environments
@code{tabular} (@pxref{tabular}) or @code{array} (@pxref{array}) because
in those the width of each column need not be constant and need not be
known in advance.

This example has a first line where the tab stops are set to explicit
widths, ended by a @code{\kill} command (which is described below):

@example
\begin@{tabbing@}
\hspace@{0.75in@}     \= \hspace@{0.40in@}  \= \hspace@{0.40in@}    \kill
Ship                \> Guns             \> Year    \\ 
\textit@{Sophie@}     \> 14               \> 1800    \\
\textit@{Polychrest@} \> 24               \> 1803    \\
\textit@{Lively@}     \> 38               \> 1804    \\
\textit@{Surprise@}   \> 28               \> 1805    \\
\end@{tabbing@}
@end example

Both the @code{tabbing} environment and the more widely-used
@code{tabular} environment put text in columns.  The most important
distinction is that in @code{tabular} the width of columns is
determined automatically by @LaTeX{}, while in @code{tabbing} the user
sets the tab stops.  Another distinction is that @code{tabular}
generates a box, but @code{tabbing} can be broken across pages.
Finally, while @code{tabular} can be used in any mode, @code{tabbing}
can be used only in paragraph mode and it starts a new paragraph.

A @code{tabbing} environment always starts a new paragraph, without
indentation. Moreover, as shown in the example above, there is no need
to use the starred form of the @code{\hspace} command at the beginning
of a tabbed row.  The right margin of the @code{tabbing} environment is
the end of line, so that the width of the environment is
@code{\linewidth}.

@cindex row, @r{tabbing}
The @code{tabbing} environment contains a sequence of @dfn{tabbed
rows}.  The first tabbed row begins immediately after
@code{\begin@{tabbing@}} and each row ends with @code{\\} or
@code{\kill}. The last row may omit the @code{\\} and end with just
@code{\end@{tabbing@}}.

At any point the @code{tabbing} environment has a current tab stop
pattern, a sequence of @math{@var{n} > 0} tab stops, numbered 0, 1,
etc.  These create @var{n} corresponding columns.  Tab stop@tie{}0 is
always the left margin, defined by the enclosing environment.  Tab
stop number@tie{}@var{i} is set if it is assigned a horizontal
position on the page.  Tab stop number@tie{}@var{i} can only be set if
all the stops 0, @dots{}, @math{i-1} have already been set; normally
later stops are to the right of earlier ones.

By default any text typeset in a @code{tabbing} environment is typeset
ragged right and left-aligned on the current tab stop. Typesetting is
done in LR mode (@pxref{Modes}).

The following commands can be used inside a @code{tabbing} environment.
They are all fragile (@pxref{\protect}).

@ftable @code
@item \\ @r{(tabbing)}
End a tabbed line and typeset it.

@item \= @r{(tabbing)}
Sets a tab stop at the current position.

@item \> @r{(tabbing)}
@findex \>
Advances to the next tab stop.

@item \<
Put following text to the left of the local margin (without changing
the margin).  Can only be used at the start of the line.

@item \+
Moves the left margin of the next and all the
following commands one tab stop to the right, beginning tabbed line if
necessary.

@item \-
Moves the left margin of the next and all the
following commands one tab stop to the left, beginning tabbed line if
necessary.

@item \' @r{(tabbing)}
Moves everything that you have typed so far in the current column, i.e.,
everything from the most recent @code{\>}, @code{\<}, @code{\'},
@code{\\}, or @code{\kill} command, to the previous column and aligned
to the right, flush against the current column's tab stop.

@item \` @r{(tabbing)}
Allows you to put text flush right against any tab stop, including tab
stop@tie{}0.  However, it can't move text to the right of the last
column because there's no tab stop there.  The @code{\`} command moves
all the text that follows it, up to the @code{\\} or
@code{\end@{tabbing@}} command that ends the line, to the right margin
of the @code{tabbing} environment.  There must be no @code{\>} or
@code{\'} command between the @code{\`} and the @code{\\} or
@code{\end@{tabbing@}} command that ends the line.

@item \a @r{(tabbing)}
@findex \a' @r{(acute accent in tabbing)}
@findex \a` @r{(grave accent in tabbing)}
@findex \a= @r{(macron accent in tabbing)}
In a @code{tabbing} environment, the commands @code{\=}, @code{\'} and
@code{\`} do not produce accents as usual (@pxref{Accents}).  Instead,
use the commands @code{\a=}, @code{\a'} and @code{\a`}.

@item \kill
Sets tab stops without producing text.  Works just like @code{\\} except
that it throws away the current line instead of producing output for it.
Any @code{\=}, @code{\+} or @code{\-} commands in that line remain in
effect.

@item \poptabs
@findex \poptabs
Restores the tab stop positions saved by the last @code{\pushtabs}.

@item \pushtabs
Saves all current tab stop positions. Useful for temporarily changing
tab stop positions in the middle of a @code{tabbing} environment.

@item \tabbingsep
Distance of the text moved by @code{\'} to left of current tab stop.

@end ftable

This example typesets a Pascal function:

@example
\begin@{tabbing@}
function \= fact(n : integer) : integer;\\
         \> begin \= \+ \\
               \> if \= n > 1 then \+ \\
                        fact := n * fact(n-1) \- \\
                  else \+ \\
                        fact := 1; \-\- \\
            end;\\
\end@{tabbing@}
@end example

@noindent
The output looks like this.

@example
function fact(n : integer) : integer;
         begin
               if n > 1 then
                  fact := n * fact(n-1);
               else
                  fact := 1;
         end;
@end example

@PkgIndex{algorithm2e} @PkgIndex{listings} @PkgIndex{minted}
@PkgIndex{fancyvrb}
@noindent
This example is just for illustration of the environment.  To actually
typeset computer code in typewriter like this, a verbatim environment
(@pxref{verbatim}) would normally be best.  For pretty-printed code,
there are quite a few packages, including @code{algorithm2e},
@code{fancyvrb}, @code{listings}, and @code{minted}.

        
@node table
@section @code{table}

@EnvIndex{table}
@cindex tables, creating
@cindex creating tables

Synopsis:

@example
\begin@{table@}[@var{placement}]
  @var{table body}
  \caption[@var{loftitle}]@{@var{title}@}  % optional
  \label@{@var{label@}}              % also optional
\end@{table@}
@end example

A class of floats (@pxref{Floats}).  They cannot be split across pages
and so they are not typeset in sequence with the normal text but instead
are floated to a convenient place, such as the top of a following page.

This example @code{table} environment contains a @code{tabular}

@example
\begin@{table@}
  \centering\small
  \begin@{tabular@}@{ll@}
    \multicolumn@{1@}@{c@}@{\textit@{Author@}@}
      &\multicolumn@{1@}@{c@}@{\textit@{Piece@}@}  \\ \hline
    Bach            &Cello Suite Number 1  \\
    Beethoven       &Cello Sonata Number 3 \\
    Brahms          &Cello Sonata Number 1
  \end@{tabular@}
  \caption@{Top cello pieces@}
  \label@{tab:cello@}
\end@{table@}
@end example

@noindent
but you can put many different kinds of content in a @code{table},
including text, @LaTeX{} commands, etc.

For the possible values of @var{placement} and their effect on the 
float placement algorithm, see @ref{Floats}.

The table body is typeset in a @code{parbox} of width @code{\textwidth}.
It can contain text, commands, graphics, etc.

The label is optional; it is used for cross references (@pxref{Cross
references}).  
@findex \caption
The @code{\caption} command is also optional.  It specifies caption text
for the table.  By default it is numbered.  If its optional
@var{lottitle} is present then that text is used in the list of tables
instead of @var{title} (@pxref{Table of contents etc.}).

In this example the table and caption will float to the bottom of a page,
unless it is pushed to a float page at the end.

@example
\begin@{table@}[b]
  \centering
  \begin@{tabular@}@{r|p@{2in@}@} \hline
    One &The loneliest number \\
    Two &Can be as sad as one.
         It's the loneliest number since the number one.
  \end@{tabular@}
  \caption@{Cardinal virtues@}
  \label@{tab:CardinalVirtues@}
\end@{table@}
@end example 


@node tabular
@section @code{tabular}

@EnvIndex{tabular}
@cindex lines in tables
@cindex lining text up in tables

Synopsis:

@example
\begin@{tabular@}[@var{pos}]@{@var{cols}@}
  @var{column 1 entry}  &@var{column 2 entry}  ...  &@var{column n entry} \\
  ...
\end@{tabular@}
@end example

@noindent
or

@example
\begin@{tabular*@}@{@var{width}@}[@var{pos}]@{@var{cols}@}
  @var{column 1 entry}  &@var{column 2 entry}  ...  &@var{column n entry} \\
  ...
\end@{tabular*@}
@end example

Produce a table, a box consisting of a sequence of horizontal rows.
Each row consists of items that are aligned vertically in columns.  This
illustrates many of the features.

@example
\begin@{tabular@}@{l|l@}
  \textit@{Player name@}  &\textit@{Career home runs@}  \\ 
  \hline
  Hank Aaron  &755 \\
  Babe Ruth   &714
\end@{tabular@}
@end example

@noindent
The output will have two left-aligned columns with a vertical bar
between them.  This is specified in @code{tabular}'s argument
@code{@{l|l@}}.
@findex & 
Put the entries into different columns by separating them with an
ampersand, @code{&}.  The end of each row is marked with a double
backslash, @code{\\}.  Put a horizontal rule below a row, after a double
backslash, with @code{\hline}.
@findex \\ @r{for @code{tabular}}
After the last row the @code{\\} is optional, unless an @code{\hline}
command follows to put a rule below the table.

The required and optional arguments to @code{tabular} consist of:

@table @var
@item pos
Optional.  Specifies the table's vertical position.  The default is to
align the table so its vertical center matches the baseline of the
surrounding text.  There are two other possible alignments: @code{t}
aligns the table so its top row matches the baseline of the surrounding
text, and @code{b} aligns on the bottom row.

This only has an effect if there is other text.  In the common case of a
@code{tabular} alone in a @code{center} environment this option makes
no difference.

@item cols
Required.  Specifies the formatting of columns.  It consists of a
sequence of the following specifiers, corresponding to the types of
column and intercolumn material.

@table @code
@item l
A column of left-aligned items.

@item r
A column of right-aligned items.

@item c
A column of centered items.

@item |
A vertical line the full height and depth of the environment.

@item @@@{@var{text or space}@}
Insert @var{text or space} at this location in every row.  The @var{text
or space} material is typeset in LR mode.  This text is fragile
(@pxref{\protect}).

If between two columns there is no @@-expression then @LaTeX{}'s
@code{book}, @code{article}, and @code{report} classes will put on
either side of each column a space of length @code{\tabcolsep}, which by
default is 6@dmn{pt}.  That is, by default adjacent columns are
separated by 12@dmn{pt} (so @code{\tabcolsep} is misleadingly named
since it is only half of the separation between tabular columns).  In
addition, a space of 6@dmn{pt} also comes before the first column and
after the final column, unless you put a @code{@@@{...@}} or @code{|}
there.

If you override the default and use an @@-expression then @LaTeX{} does
not insert @code{\tabcolsep} so you must insert any desired space
yourself, as in @code{@@@{\hspace@{1em@}@}}.

An empty expression @code{@@@{@}} will eliminate the space. In
particular, sometimes you want to eliminate the space before the first
column or after the last one, as in the example below where the
tabular lines need to lie on the left margin.

@example
\begin@{flushleft@}
  \begin@{tabular@}@{@@@{@}l@}
    ...
  \end@{tabular@}
\end@{flushleft@}
@end example

The next example shows text, a decimal point between the columns,
arranged so the numbers in the table are aligned on it.

@example 
\begin@{tabular@}@{r@@@{$.$@}l@}
  $3$ &$14$  \\
  $9$ &$80665$
\end@{tabular@}
@end example

@findex \extracolsep
An @code{\extracolsep@{@var{wd}@}} command in an @@-expression causes an
extra space of width @var{wd} to appear to the left of all subsequent
columns, until countermanded by another @code{\extracolsep}.  Unlike
ordinary intercolumn space, this extra space is not suppressed by an
@@-expression.  An @code{\extracolsep} command can be used only in an
@@-expression in the @code{cols} argument.  Below, @LaTeX{} inserts the
right amount of intercolumn space to make the entire table 4 inches
wide.

@example
\begin@{tabular*@}@{4in@}@{l@@@{\extracolsep@{\fill@}@}l@}
  Seven times down, eight times up \ldots 
  &such is life!
\end@{tabular*@}
@end example

To insert commands that are automatically executed before a given
column, load the @code{array} package and use the @code{>@{...@}}
specifier.
@c xx should fully explain array, tabularx, and all other base packages...

@item p@{@var{wd}@}
Each item in the column is typeset in a parbox of width @var{wd}, as if
it were the argument of a @code{\parbox[t]@{wd@}@{...@}} command.

A line break double backslash @code{\\} may not appear in the item,
except inside an environment like @code{minipage}, @code{array}, or
@code{tabular}, or inside an explicit @code{\parbox}, or in the scope of
a @code{\centering}, @code{\raggedright}, or @code{\raggedleft}
declaration (when used in a @code{p}-column element these declarations
must appear inside braces, as with @code{@{\centering .. \\
..@}}). Otherwise @LaTeX{} will misinterpret the double backslash as
ending the row.  Instead, to get a line break in there use
@code{\newline} (@pxref{\newline}).

@item *@{@var{num}@}@{@var{cols}@}
Equivalent to @var{num} copies of @var{cols}, where @var{num} is a
positive integer and @var{cols} is a list of specifiers.  Thus the
specifier @code{\begin@{tabular@}@{|*@{3@}@{l|r@}|@}} is equivalent to
the specifier @code{\begin@{tabular@}@{|l|rl|rl|r|@}}.  Note that
@var{cols} may contain another @code{*}-expression.
 
@end table

@item width
Required for @code{tabular*}, not allowed for @code{tabular}. Specifies
the width of the @code{tabular*} environment.  The space between columns
should be rubber, as with @code{@@@{\extracolsep@{\fill@}@}}, to allow
the table to stretch or shrink to make the specified width, or else you
are likely to get the @code{Underfull \hbox (badness 10000) in alignment
...} warning.

@end table

Parameters that control formatting:
@c xx defaults, own node (xref from array)?

@ftable @code
@item \arrayrulewidth
@anchor{tabular arrayrulewidth}
A length that is the thickness of the rule created by @code{|},
@code{\hline}, and @code{\vline} in the @code{tabular} and @code{array}
environments.  The default is @samp{.4pt}. Change it as in
@code{\setlength@{\arrayrulewidth@}@{0.8pt@}}.

@item \arraystretch
@anchor{tabular arraystrech}
A factor by which the spacing between rows in the @code{tabular} and
@code{array} environments is multiplied.  The default is @samp{1}, for
no scaling.  Change it as @code{\renewcommand@{\arraystretch@}@{1.2@}}.

@item \doublerulesep
@anchor{tabular doublerulesep}
A length that is the distance between the vertical rules produced by the
@code{||} specifier.  The default is @samp{2pt}.

@item \tabcolsep
@anchor{tabular tabcolsep}
A length that is half of the space between columns. The default is
@samp{6pt}.  Change it with @code{\setlength}.

@end ftable

The following commands can be used inside the body of a @code{tabular}
environment, the first two inside an entry and the second two between
lines:

@menu
* \multicolumn::        Make an item spanning several columns.
* \vline::              Draw a vertical line.
* \cline::              Draw a horizontal line spanning some columns.
* \hline::              Draw a horizontal line spanning all columns.
@end menu


@node \multicolumn
@subsection @code{\multicolumn}

@findex \multicolumn

Synopsis:

@example
\multicolumn@{@var{numcols}@}@{@var{cols}@}@{@var{text}@}
@end example

Make an @code{array} or @code{tabular} entry that spans several columns.
The first argument @var{numcols} gives the number of columns to span.
The second argument @var{cols} specifies the formatting of the entry,
with @code{c} for centered, @code{l} for flush left, or @code{r} for
flush right.  The third argument @var{text} gives the contents of that
entry.

In this example, in the first row, the second and third columns are
spanned by the single heading @samp{Name}.

@example
\begin@{tabular@}@{lccl@} 
  \textit@{ID@}       &\multicolumn@{2@}@{c@}@{\textit@{Name@}@} &\textit@{Age@} \\
  \hline  
  978-0-393-03701-2 &O'Brian &Patrick                  &55           \\
    ...
\end@{tabular@}
@end example

What counts as a column is:@tie{}the column format specifier for the
@code{array} or @code{tabular} environment is broken into parts, where
each part (except the first) begins with @code{l}, @code{c}, @code{r},
or@tie{}@code{p}.  So from @code{\begin@{tabular@}@{|r|ccp@{1.5in@}|@}}
the parts are @code{|r|}, @code{c}, @code{c},
and@tie{}@code{p@{1.5in@}|}.

The @var{cols} argument overrides the @code{array} or @code{tabular}
environment's intercolumn area default adjoining this multicolumn
entry. To affect that area, this argument can contain vertical bars
@code{|} indicating the placement of vertical rules, and @code{@@@{...@}}
expressions.  Thus if @var{cols} is @samp{|c|} then this multicolumn
entry will be centered and a vertical rule will come in the intercolumn
area before it and after it.  This table details the exact behavior.

@example
\begin@{tabular@}@{|cc|c|c|@}
  \multicolumn@{1@}@{r@}@{w@}       % entry one
    &\multicolumn@{1@}@{|r|@}@{x@}  % entry two 
    &\multicolumn@{1@}@{|r@}@{y@}   % entry three
    &z                        % entry four
\end@{tabular@}
@end example

@noindent
Before the first entry the output will not have a vertical rule because
the @code{\multicolumn} has the @var{cols} specifier @samp{r} with no
initial vertical bar.  Between entry one and entry two there will be a
vertical rule; although the first @var{cols} does not have an ending
vertical bar, the second @var{cols} does have a starting one.  Between
entry two and entry three there is a single vertical rule; despite that
the @var{cols} in both of the surrounding @code{multicolumn}'s call for
a vertical rule, you only get one rule.  Between entry three and entry
four there is no vertical rule; the default calls for one but the
@var{cols} in the entry three @code{\multicolumn} leaves it out, and
that takes precedence.  Finally, following entry four there is a
vertical rule because of the default.

The number of spanned columns @var{numcols} can be 1.  Besides giving
the ability to change the horizontal alignment, this also is useful to
override for one row the @code{tabular} definition's default intercolumn
area specification, including the placement of vertical rules.

In the example below, in the @code{tabular} definition the first column
is specified to default to left justified but in the first row the entry
is centered with @code{\multicolumn@{1@}@{c@}@{\textsc@{Period@}@}}.
Also in the first row, the second and third columns are spanned by a
single entry with @code{\multicolumn@{2@}@{c@}@{\textsc@{Span@}@}},
overriding the specification to center those two columns on the page
range en-dash.

@example
\begin@{tabular@}@{l|r@@@{--@}l@} 
  \multicolumn@{1@}@{c@}@{\textsc@{Period@}@}  
    &multicolumn@{2@}@{c@}@{\textsc@{Span@}@} \\ \hline
  Baroque          &1600           &1760         \\
  Classical        &1730           &1820         \\
  Romantic         &1780           &1910         \\
  Impressionistic  &1875           &1925
\end@{tabular@}
@end example

@noindent
Although the @code{tabular} specification by default puts a vertical
rule between the first and second columns, no such vertical rule appears
in the first row here.  That's because there is no vertical bar in the
@var{cols} part of the first row's first @code{\multicolumn} command.


@node \vline
@subsection @code{\vline}

@findex \vline
Draw a vertical line in a @code{tabular} or @code{array} environment
extending the full height and depth of an entry's row.  Can also be
used in an @@-expression, although its synonym vertical
bar@tie{}@code{|} is more common.  This command is rarely used in the
body of a table; typically a table's vertical lines are specified in
@code{tabular}'s @var{cols} argument and overridden as needed with
@code{\multicolumn} (@pxref{tabular}).

The example below illustrates some pitfalls.  In the first row's second
entry the @code{\hfill} moves the @code{\vline} to the left edge of the
cell.  But that is different than putting it halfway between the two
columns, so between the first and second columns there are two vertical
rules, with the one from the @code{@{c|cc@}} specifier coming before the
one produced by the @code{\vline\hfill}.  In contrast, the first row's
third entry shows the usual way to put a vertical bar between two
columns.  In the second row, the @code{ghi} is the widest entry in its
column so in the @code{\vline\hfill} the @code{\hfill} has no effect and
the vertical line in that entry appears immediately next to the
@code{g}, with no whitespace.

@example
\begin@{tabular@}@{c|cc@}
  x   &\vline\hfill y   &\multicolumn@{1@}@{|r@}@{z@} \\ % row 1  
  abc &def &\vline\hfill ghi                       % row 2  
\end@{tabular@}
@end example


@node \cline
@subsection @code{\cline}

@findex \cline

Synopsis:

@example
\cline@{@var{i}-@var{j}@}
@end example

In an @code{array} or @code{tabular} environment, draw a horizontal rule
beginning in column@tie{}@var{i} and ending in column@tie{}@var{j}. The
dash, @code{-}, must appear in the mandatory argument. To span a single
column use the number twice, as with @code{\cline@{2-2@}}.

This example puts two horizontal lines between the first and second
rows, one line in the first column only, and the other spanning the
third and fourth columns.  The two lines are side-by-side, at the same
height.

@example
\begin@{tabular@}@{llrr@} 
  a &b &c &d \\ \cline@{1-1@} \cline@{3-4@} 
  e &f &g &h 
\end@{tabular@}
@end example


@node \hline
@subsection @code{\hline}

@findex \hline

Draw a horizontal line the width of the enclosing @code{tabular} or
@code{array} environment.  It's most commonly used to draw a line at the
top, bottom, and between the rows of a table.

In this example the top of the table has two horizontal rules, one above
the other, that span both columns.  The bottom of the table has a single
rule spanning both columns.  Because of the @code{\hline}, the
@code{tabular} second row's line ending double backslash@tie{}@code{\\}
is required.

@example
\begin@{tabular@}@{ll@} \hline\hline
  Baseball   &Red Sox  \\
  Basketball &Celtics  \\ \hline
\end@{tabular@}
@end example


@node thebibliography
@section @code{thebibliography}

@EnvIndex{thebibliography}
@cindex bibliography, creating (manually)

Synopsis:

@example
\begin@{thebibliography@}@{@var{widest-label}@}
  \bibitem[@var{label}]@{@var{cite_key@}}
  ...
\end@{thebibliography@}
@end example

Produce a bibliography or reference list.  There are two ways to produce
bibliographic lists.  This environment is suitable when you have only a
few references and can maintain the list by hand.  @xref{Using BibTeX}
for a more sophisticated approach.

This shows the environment with two entries.

@example
This work is based on \cite@{latexdps@}.
Together they are \cite@{latexdps, texbook@}.
  ...
\begin@{thebibliography@}@{9@}
\bibitem@{latexdps@} 
  Leslie Lamport. 
  \textit@{\LaTeX@{@}: a document preparation system@}. 
  Addison-Wesley, Reading, Massachusetts, 1993.
\bibitem@{texbook@} 
  Donald Ervin Knuth. 
  \textit@{The \TeX book@}. 
  Addison-Wesley, Reading, Massachusetts, 1983.
\end@{thebibliography@}
@end example

@noindent
This styles the first reference as @samp{[1] Leslie ...}, and so that
@code{\cite@{latexdps@}} produces the matching @samp{... based on [1]}.
The second @code{\cite} produces @samp{[1, 2]}.  You must compile the
document twice to resolve these references.

The mandatory argument @var{widest-label} is text that, when typeset, is
as wide as the widest item label produced by the @code{\bibitem}
commands.  The tradition is to use @code{9} for bibliographies with less
than 10 references, @code{99} for ones with less than 100, etc.

The bibliographic list is headed by a title such as @samp{Bibliography}.
To change it there are two cases.  In the @file{book} and @file{report}
classes, where the top level sectioning is @code{\chapter} and the
default title is @samp{Bibliography}, that title is in the macro
@code{\bibname}.  For @file{article}, where the class's top level
sectioning is @code{\section} and the default is @samp{References}, the
title is in macro @code{\refname}.  Change it by redefining the command,
as with @code{\renewcommand@{\refname@}@{Cited references@}} after
@code{\begin@{document@}}.

@PkgIndex{babel}
Language support packages such as @file{babel} will automatically
redefine @code{\refname} or @code{\bibname} to fit the selected
language.

@menu
* \bibitem::            Specify a bibliography item.
* \cite::               Refer to a bibliography item.
* \nocite::             Include an item in the bibliography.
* Using BibTeX::        Automatic generation of bibliographies.
@end menu


@node \bibitem
@subsection @code{\bibitem}

@findex \bibitem

Synopsis:

@example
\bibitem@{@var{cite_key}@}
@end example

@noindent
or

@example
\bibitem[@var{label}]@{@var{cite_key}@}
@end example

Generate an entry labeled by @var{label}.  The default is for @LaTeX{} to
generates a number using the @code{enumi} counter.  The @dfn{citation key} 
@cindex citation key
@var{cite_key} is a string of
letters, numbers, and punctuation symbols (but not comma).

@xref{thebibliography} for an example.

The optional @var{label} changes the default label from an integer to the
given string.  With this

@example
\begin@{thebibliography@}
\bibitem[Lamport 1993]@{latexdps@} 
  Leslie Lamport. 
  \textit@{\LaTeX@{@}: a document preparation system@}. 
  Addison-Wesley, Reading, Massachusetts, 1993.
\bibitem@{texbook@} 
  Donald Ervin Knuth. 
  \textit@{The \TeX book@}. 
  Addison-Wesley, Reading, Massachusetts, 1983.
\end@{thebibliography@}
@end example

@noindent
the first entry will be styled as @samp{[Lamport 1993] Leslie ...}  (The
amount of horizontal space that @LaTeX{} leaves for the label depends on
the @var{widest-label} argument of the @code{thebibliography}
environment; see @ref{thebibliography}.)  Similarly, @code{... based on
\cite@{latexdps@}} will produce @samp{... based on [Lamport 1994]}.

If you mix @code{\bibitem} entries having a @var{label} with those that
do not then @LaTeX{} will number the unlabelled ones sequentially.  In
the example above the @code{texbook} entry will appear as @samp{[1]
Donald ...}, despite that it is the second entry.

If you use the same @var{cite_key} twice then you get @samp{LaTeX
Warning: There were multiply-defined labels}.

Under the hood, @LaTeX{} remembers the @var{cite_key} and @var{label}
information because @code{\bibitem} writes it to the auxiliary file
@file{@var{filename}.aux}.  For instance, the above example causes
@code{\bibcite@{latexdps@}@{Lamport, 1993@}} and
@code{\bibcite@{texbook@}@{1@}} to appear in that file.  The @file{.aux}
file is read by the @code{\begin@{document@}} command and then the
information is available for @code{\cite} commands.  This explains why
you need to run @LaTeX{} twice to resolve references: once to write it
out and once to read it in.

Because of this two-pass algorithm, when you add a @code{\bibitem} or
change its @var{cite_key} you may get @samp{LaTeX Warning: Label(s) may
have changed. Rerun to get cross-references right}.  Fix it by
recompiling.


@node \cite
@subsection @code{\cite}

@findex \cite

Synopsis:

@example
\cite@{@var{keys}@}
@end example

@noindent
or

@example
\cite[@var{subcite}]@{@var{keys}@}
@end example

Generate as output a citation to the references associated with
@var{keys}.  The mandatory @var{keys} is a citation key, or a
comma-separated list of citation keys (@pxref{\bibitem}).

This 

@example
The ultimate source is \cite@{texbook@}.
  ...
\begin@{thebibliography@}
\bibitem@{texbook@} 
  Donald Ervin Knuth. 
  \textit@{The \TeX book@}. 
  Addison-Wesley, Reading, Massachusetts, 1983.
\end@{thebibliography@}
@end example

@noindent
produces output like @samp{... source is [1]}.  (You can change the
appearance of the citation with bibliography styles.  More is in
@ref{Using BibTeX}.)

The optional argument @var{subcite} is appended to the citation.  For
example, @code{See 14.3 in \cite[p.~314]@{texbook@}} might produce
@samp{See 14.3 in [1, p.@tie{}314]}.

In addition to what appears in the output, @code{\cite} writes
information to the auxiliary file @file{@var{filename}.aux}.  For
instance, @code{\cite@{latexdps@}} writes @samp{\citation@{latexdps@}}
to that file.  This information is used by Bib@TeX{} to include in your
reference list only those works that you have actually cited; see
@ref{\nocite} also.

If @var{keys} is not in your bibliography information then you get
@samp{LaTeX Warning: There were undefined references}, and in the output
the citation shows as a boldface question mark between square brackets.
There are two possible causes.  If you have mistyped something, as in
@code{\cite@{texbok@}} then you need to correct the spelling.  On the
other hand, if you have just added or modified the bibliographic
information and so changed the @file{.aux} file (@pxref{\bibitem}) then
the fix may be to run @LaTeX{} again.


@node \nocite
@subsection @code{\nocite}

@findex \nocite

Synopsis:

@example
@code{\nocite@{@var{keys}@}}
@end example

Produces no output but writes @var{keys} to the auxiliary file
@file{@var{doc-filename}.aux}.

The mandatory argument @var{keys} is a comma-separated list of one or
more citation keys (@pxref{\bibitem}).  This information is used by
Bib@TeX{} to include these works in your reference list even though you
have not cited them (@pxref{\cite}).


@node Using BibTeX
@subsection Using Bib@TeX{}

@cindex using Bib@TeX{}
@cindex bib@TeX{}, using
@cindex bibliography, creating (automatically)
@findex \bibliographystyle
@findex \bibliography

As described in @code{thebibliography} (@pxref{thebibliography}), a
sophisticated approach to managing bibliographies is provided by the
Bib@TeX{} program.  This is only an introduction; see the full
documentation on CTAN.

With Bib@TeX{}, you don't use @code{thebibliography}
(@pxref{thebibliography}). Instead, include these lines.

@example
\bibliographystyle@{@var{bibstyle}@}
\bibliography@{@var{bibfile1}, @var{bibfile2}, ...@}
@end example

@noindent
The @var{bibstyle} refers to a file @file{@var{bibstyle}.bst}, which
defines how your citations will look.  The standard @var{bibstyle}'s
distributed with Bib@TeX{} are:

@table @code
@item alpha
Labels are formed from name of author and year of publication.
The bibliographic items are sorted alphabetically.
@item plain
Labels are integers.
Sort the  bibliographic items alphabetically.
@item unsrt
Like @code{plain}, but entries are in order of citation.
@item abbrv
Like @code{plain}, but more compact labels.
@end table

@noindent Many, many other Bib@TeX{} style files exist,
tailored to the demands of various publications.  See CTAN's listing
@url{http://mirror.ctan.org/biblio/bibtex/contrib}.

The @code{\bibliography} command is what actually produces the
bibliography.  Its argument is a comma-separated list, referring to
files named @file{@var{bibfile1}.bib}, @file{@var{bibfile2}.bib},
@dots{} These contain your database in Bib@TeX{} format.  This shows a
typical couple of entries in that format.

@example
@@book@{texbook,
  title     = @{The @{@{\TeX@}@}book@},
  author    = @{D.E. Knuth@},
  isbn      = @{0201134489@},
  series    = @{Computers \& typesetting@},
  year      = @{1983@},
  publisher = @{Addison-Wesley@}
@}
@@book@{sexbook,
    author    = @{W.H. Masters and V.E. Johnson@},
    title     = @{Human Sexual Response@},
    year      = @{1966@},
    publisher = @{Bantam Books@}
@}
@end example

Only the bibliographic entries referred to via @code{\cite} and
@code{\nocite} will be listed in the document's bibliography.  Thus you
can keep all your sources together in one file, or a small number of
files, and rely on Bib@TeX{} to include in this document only those that
you used.


@node theorem
@section @code{theorem}

@EnvIndex{theorem}
@cindex theorems, typesetting

Synopsis:

@example
\begin@{theorem@}
  @var{theorem body}
\end@{theorem@}
@end example

Produces @samp{Theorem @var{n}} in boldface followed by @var{theorem
body} in italics.  The numbering possibilities for @var{n} are described under
@code{\newtheorem} (@pxref{\newtheorem}).

@example
\newtheorem@{lem@}@{Lemma@}      % in preamble
\newtheorem@{thm@}@{Theorem@}    
  ...
\begin@{lem@}                  % in  document body
  text of lemma
\end@{lem@}

The next result follows immediately.
\begin@{thm@}[Gauss]   %  put `Gauss' in parens after theorem head
  text of theorem
\end@{thm@}
@end example

@PkgIndex{amsmath}
@PkgIndex{amsthm}
Most new documents use the packages @code{amsthm} and @code{amsmath}
from the American Mathematical Society.  Among other things these
packages include a large number of options for theorem environments,
such as styling options.


@node titlepage
@section @code{titlepage}

@EnvIndex{titlepage}
@cindex making a title page
@cindex title pages, creating

Synopsis:

@example
\begin@{titlepage@}
  ... text and spacing ...
\end@{titlepage@}
@end example

Create a title page, a page with no printed page number or heading and
with succeeding pages numbered starting with page one.

In this example all formatting, including vertical spacing, is left to
the author.

@example
\begin@{titlepage@}
\vspace*@{\stretch@{1@}@}
\begin@{center@}
  @{\huge\bfseries Thesis \\[1ex] 
                  title@}                  \\[6.5ex]
  @{\large\bfseries Author name@}           \\
  \vspace@{4ex@}
  Thesis  submitted to                    \\[5pt]
  \textit@{University name@}                \\[2cm]
  in partial fulfilment for the award of the degree of \\[2cm]
  \textsc@{\Large Doctor of Philosophy@}    \\[2ex]
  \textsc@{\large Mathematics@}             \\[12ex]
  \vfill
  Department of Mathematics               \\
  Address                                 \\
  \vfill
  \today
\end@{center@}
\vspace@{\stretch@{2@}@}
\end@{titlepage@}
@end example

To instead produce a standard title page without a @code{titlepage}
environment, use @code{\maketitle} (@pxref{\maketitle}).


@node verbatim
@section @code{verbatim}

@EnvIndex{verbatim}
@cindex verbatim text
@cindex simulating typed text
@cindex typed text, simulating
@cindex code, typesetting
@cindex computer programs, typesetting

Synopsis:

@example
\begin@{verbatim@}
@var{literal-text}
\end@{verbatim@}
@end example

A paragraph-making environment in which @LaTeX{} produces as output
exactly what you type as input.  For instance inside @var{literal-text}
the backslash@tie{}@code{\} character does not start commands, it
produces a printed @samp{\}, and carriage returns and blanks are taken
literally.  The output appears in a monospaced typewriter-like font
(@code{\tt}).

@example
\begin@{verbatim@}
Symbol swearing: %&$#?@!.
\end@{verbatim@}
@end example

The only restriction on @code{literal-text} is that it cannot include
the string @code{\end@{verbatim@}}.

@PkgIndex{cprotect}
You cannot use the verbatim environment in the argument to macros, for
instance in the argument to a @code{\section}.  This is not the same as
commands being fragile (@pxref{\protect}), instead it just cannot appear
there. (But the @code{cprotect} package can help with this.)

@PkgIndex{listings}
@PkgIndex{minted}
One common use of verbatim input is to typeset computer code.  There are
packages that are an improvement the @code{verbatim} environment.  For
instance, one improvement is to allow the verbatim inclusion of external
files, or parts of those files.  Such packages include @code{listings},
and @code{minted}.

@PkgIndex{fancyvrb}
@PkgIndex{verbatimbox}
A package that provides many more options for verbatim environments is
@code{fancyvrb}.  Another is @code{verbatimbox}.

For a list of all the relevant packages, see CTAN.

@menu
* \verb::       The macro form of the @code{verbatim} environment.
@end menu


@node \verb
@subsection @code{\verb}

@findex \verb
@cindex verbatim text, inline

Synopsis:

@example
\verb @var{char} @var{literal-text} @var{char}
\verb* @var{char} @var{literal-text} @var{char}
@end example

Typeset @var{literal-text} as it is input, including special characters
and spaces, using the typewriter (@code{\tt}) font.

This example shows two different invocations of @code{\verb}.

@example
This is \verb!literally! the biggest pumpkin ever.
And this is the best squash, \verb+literally!+
@end example

@noindent
The first @code{\verb} has its @var{literal-text} surrounded with
exclamation point, @code{!}.  The second instead uses plus, @code{+},
because the exclamation point is part of @code{literal-text}.

The single-character delimiter @var{char} surrounds
@var{literal-text}@tie{}--- it must be the same character before and
after.  No spaces come between @code{\verb} or @code{\verb*} and
@var{char}, or between @var{char} and @var{literal-text}, or between
@var{literal-text} and the second occurrence of @var{char} (the synopsis
shows a space only to distinguish one component from the other).  The
delimiter must not appear in @var{literal-text}. The @var{literal-text}
cannot include a line break.

@cindex visible space
The @code{*}-form differs only in that spaces are printed with a visible
space character.
@tex
(Namely, {\tt\char`\ }.)
@end tex

The output from this will include a character showing the spaces.

@example
The commands's first argument is \verb*!filename with extension! and ...
@end example

@PkgIndex{url}
For typesetting Internet addresses, urls, the package @code{url}
provides an option that is better than the @code{\verb} command, since
it allows line breaks.

@PkgIndex{listings}
@PkgIndex{minted}
For computer code there are many packages with advantages over
@code{\verb}.  One is @file{listings}, another is @file{minted}.

@PkgIndex{cprotect}
You cannot use @code{\verb} in the argument to a macro, for instance in
the argument to a @code{\section}.  It is not a question of @code{\verb}
being fragile (@pxref{\protect}), instead it just cannot appear there.
(But the @code{cprotect} package can help with this.)


@node verse
@section @code{verse}

@EnvIndex{verse}
@cindex poetry, an environment for

Synopsis:

@example
\begin@{verse@}
  @var{line1} \\
  @var{line2} \\
  ...
\end@{verse@}
@end example

An environment for poetry.

Here are two lines from Shakespeare's Romeo and Juliet.

@example
Then plainly know my heart's dear love is set \\
On the fair daughter of rich Capulet.
@end example

@findex \\ @r{for @code{verse}}
Separate the lines of each stanza with @code{\\}, and use one or more
blank lines to separate the stanzas.

@example
\begin@{verse@}
\makebox[\linewidth][c]@{\textit@{Shut Not Your Doors@} ---Walt Whitman@}
  \\[1\baselineskip]
Shut not your doors to me proud libraries,                  \\
For that which was lacking on all your well-fill'd shelves, \\
\qquad yet needed most, I bring,                             \\
Forth from the war emerging, a book I have made,            \\
The words of my book nothing, the drift of it every thing,  \\
A book separate, not link'd with the rest nor felt by the intellect, \\
But you ye untold latencies will thrill to every page.
\end@{verse@}
@end example

@noindent
The output has margins indented on the left and the right, paragraphs
are not indented, and the text is not right-justified.


@node Line breaking
@chapter Line breaking

@cindex line breaking
@cindex breaking lines

The first thing @LaTeX{} does when processing ordinary text is to
translate your input file into a sequence of glyphs and spaces.  To
produce a printed document, this sequence must be broken into lines
(and these lines must be broken into pages).

@LaTeX{} usually does the line (and page) breaking in the text body for
you but in some environments you manually force line breaks.

A common workflow is to get a final version of the document content
before taking a final pass through and considering line breaks (and page
breaks).  This differs from word processing, where you are formatting
text as you input it.  Putting these off until the end prevents a lot of
fiddling with breaks that will change anyway.

@menu
* \\::                         Start a new line.
* \obeycr & \restorecr::       Make each input line start a new output line.
* \newline::                   Break the line
* \- (hyphenation)::           Insert explicit hyphenation.
* \discretionary::             Explicit control of the hyphen character.
* \fussy & \sloppy::           Be more or less particular with line breaking.
* \hyphenation::               Tell @LaTeX{} how to hyphenate a word.
* \linebreak & \nolinebreak::  Forcing & avoiding line breaks.
@end menu


@node \\
@section @code{\\}

@findex \\ @r{force line break}
@cindex new line, starting
@cindex line break, forcing

Synopsis, one of:

@example
\\
\\[@var{morespace}]
@end example

@noindent
or one of: 

@example
\\*
\\*[@var{morespace}]
@end example

End the current line.  The optional argument @var{morespace} specifies
extra vertical space to be inserted before the next line.  This is a
rubber length (@pxref{Lengths}) and can be negative.  The text before
the line break is set at its normal length, that is, it is not stretched
to fill out the line width.  This command is fragile (@pxref{\protect}).

The starred form, @code{\\*}, tells @LaTeX{} not to start a new page
between the two lines, by issuing a @code{\nobreak}.

@example
\title@{My story: \\[0.25in]
       a tale of woe@}
@end example

Explicit line breaks in the main text body are unusual in @LaTeX{}.  In
particular, don't start new paragraphs with @code{\\}.  Instead leave a
blank line between the two paragraphs.  And don't put in a sequence of
@code{\\}'s to make vertical space. Instead use
@code{\vspace@{@var{length}@}}, or
@code{\leavevmode\vspace@{@var{length}@}}, or
@code{\vspace*@{@var{length}@}} if you want the space to not be thrown
out at the top of a new page (@pxref{\vspace}).

The @code{\\} command is mostly used outside of the main flow of text
such as in a @code{tabular} or @code{array} environment or in an
equation environment.

The @code{\\} command is a synonym for @code{\newline}
(@pxref{\newline}) under ordinary circumstances (an example of an
exception is the @code{p@{...@}} column in a @code{tabular}
environment; @pxref{tabular}).

@c credit: David Carlisle https://tex.stackexchange.com/a/82666
The @code{\\} command is a macro, and its definition changes by context
so that its definition in normal text, a @code{center} environment, a
@code{flushleft} environment, and a @code{tabular} are all different.
In normal text when it forces a linebreak it is essentially a shorthand
for @code{\newline}.  It does not end horizontal mode or end the
paragraph, it just inserts some glue and penalties so that when the
paragraph does end a linebreak will occur at that point, with the short
line padded with white space.

You get @samp{LaTeX Error: There's no line here to end} if you use
@code{\\} to ask for a new line, rather than to end the current line.
An example is if you have @code{\begin@{document@}\\} or, more likely,
something like this.

@example
\begin@{center@}
  \begin@{minipage@}@{0.5\textwidth@}
  \\
  In that vertical space put your mark.
  \end@{minipage@}
\end@{center@}
@end example

@noindent
Fix it by replacing the double backslash with something like
@code{\vspace@{\baselineskip@}}.


@node \obeycr & \restorecr
@section @code{\obeycr} & @code{\restorecr}

@findex \obeycr
@findex \restorecr
@cindex new line, output as input

The @code{\obeycr} command makes a return in the input file (@samp{^^M},
internally) the same as @code{\\}, followed by @code{\relax}.  So each
new line in the input will also be a new line in the output.  The
@code{\restorecr} command restores normal line-breaking behavior.

This is not the way to show verbatim text or computer code.
@xref{verbatim} instead.

With @LaTeX{}'s usual defaults, this

@example
aaa
bbb

\obeycr
ccc
ddd
   eee

\restorecr
fff
ggg

hhh
iii
@end example

@noindent
produces output like this.

@example
  aaa bbb
  ccc
ddd
eee

fff ggg
  hhh iii
@end example

@noindent
The indents are paragraph indents.


@node \newline
@section @code{\newline}

@findex \newline
@cindex new line, starting (paragraph mode)

In ordinary text, this ends a line in a way that does not right-justify
the line, so the prior text is not stretched. That is, in paragraph mode
(@pxref{Modes}), the @code{\newline} command is equivalent to
double-backslash (@pxref{\\}).  This command is fragile
(@pxref{\protect}).

However, the two commands are different inside a @code{tabular} or
@code{array} environment. In a column with a specifier producing a
paragraph box such as typically @code{p@{...@}}, @code{\newline} will
insert a line end inside of the column; that is, it does not break the
entire tabular row.  To break the entire row use @code{\\} or its
equivalent @code{\tabularnewline}.

This will print @samp{Name:} and @samp{Address:} as two lines in a
single cell of the table.

@example
\begin@{tabular@}@{p@{1in@}@{\hspace@{2in@}@}p@{1in@}@}
  Name: \newline Address: &Date: \\ \hline
\end@{tabular@}
@end example

@noindent
The @samp{Date:} will be baseline-aligned with @samp{Name:}.


@node \- (hyphenation)
@section @code{\-} (discretionary hyphen)

@findex \- @r{(hyphenation)}
@cindex hyphenation, forcing

Tell @LaTeX{} that it may hyphenate the word at that point.  When you
insert @code{\-} commands in a word, the word will only be hyphenated at
those points and not at any of the hyphenation points that @LaTeX{}
might otherwise have chosen.  This command is robust (@pxref{\protect}).

@LaTeX{} is good at hyphenating and usually finds most of the correct
hyphenation points, while almost never using an incorrect one.  The
@code{\-} command is for exceptional cases.

For example, @LaTeX{} does not ordinarily hyphenate words containing a
hyphen.  Below, the long and hyphenated word means @LaTeX{} has to put
in unacceptably large spaces to set the narrow column.

@example
\begin@{tabular@}@{rp@{1.75in@}@}
  Isaac Asimov &The strain of
               anti-intellectualism
               % an\-ti-in\-tel\-lec\-tu\-al\-ism
               has been a constant thread winding its way through our
               political and cultural life, nurtured by
               the false notion that democracy means that
               `my ignorance is just as good as your knowledge'.
\end@{tabular@}
@end example

@noindent
Commenting out the third line and uncommenting the fourth makes a much
better fit.

The @code{\-} command only allows @LaTeX{} to break there, it does not
require that it break there.  You can insist on a split with something
like @code{Hef-\linebreak feron}.  Of course, if you later change the
text then this forced break may look very odd, so this approach requires
care.


@node \discretionary
@section @code{\discretionary} (generalized hyphenation point)
@cindex hyphenation, discretionary
@cindex discretionary hyphenation

Synopsis:

@example
\discretionary@{@var{pre-break}@}@{@var{post-break}@}@{@var{no-break}@}
@end example

Handle word changes around hyphens.  This command is not often used in
@LaTeX{} documents.

If a line break occurs at the point where @code{\discretionary} appears
then @TeX{} puts @var{pre-break} at the end of the current line and puts
@var{post-break} at the start of the next line.  If there is no line
break here then @TeX{} puts @var{no-break}

In @samp{difficult} the three letters @code{ffi} form a ligature.  But
@TeX{} can nonetheless break between the two f's with this.

@example
di\discretionary@{f-@}@{fi@}@{ffi@}cult
@end example

Note that users do not have to do this.  It is typically handled
automatically by @TeX{}'s hyphenation algorithm.


@node \fussy & \sloppy
@section @code{\fussy} & @code{\sloppy}

@findex \fussy
@findex \sloppy
@cindex line breaks, changing

Declarations to make @TeX{} more picky or less picky about line
breaking.  Declaring @code{\fussy} usually avoids too much space between
words, at the cost of an occasional overfull box.  Conversely,
@code{\sloppy} avoids overfull boxes while suffering loose interword
spacing.

The default is @code{\fussy}.  Line breaking in a paragraph is
controlled by whichever declaration is current at the blank line, or
@code{\par}, or displayed equation ending that paragraph.  So to affect
the line breaks, include that paragraph-ending material in the scope of
the command.

@menu
* sloppypar::          Environment version of \sloppy command.
@end menu


@node sloppypar
@subsection @code{sloppypar}

@findex sloppypar
@cindex sloppypar environment

Synopsis:

@example
\begin@{sloppypar@}
  ... paragraphs ...
\end@{sloppypar@}
@end example

Typeset the paragraphs with @code{\sloppy} in effect (@pxref{\fussy &
\sloppy}).  Use this to locally adjust line breaking, to avoid
@samp{Overfull box} or @samp{Underfull box} errors.

The example is simple.

@example
\begin@{sloppypar@}
  Her plan for the morning thus settled, she sat quietly down to her
  book after breakfast, resolving to remain in the same place and the
  same employment till the clock struck one; and from habitude very
  little incommoded by the remarks and ejaculations of Mrs.\ Allen,
  whose vacancy of mind and incapacity for thinking were such, that
  as she never talked a great deal, so she could never be entirely
  silent; and, therefore, while she sat at her work, if she lost her
  needle or broke her thread, if she heard a carriage in the street,
  or saw a speck upon her gown, she must observe it aloud, whether
  there were anyone at leisure to answer her or not.
\end@{sloppypar@}
@end example


@node \hyphenation
@section @code{\hyphenation}

@findex \hyphenation
@cindex hyphenation, defining

Synopsis:

@example
\hyphenation@{@var{word1} ...@}
@end example

Declares allowed hyphenation points within the words in the list.  The
words in that list are separated by spaces.  Show permitted points for
hyphenation with a dash character, @code{-}.

Here is an example:

@example
\hyphenation@{hat-er il-lit-e-ra-ti tru-th-i-ness@}
@end example

Use lowercase letters.  @TeX{} will only hyphenate if the word matches
exactly.  Multiple @code{\hyphenation} commands accumulate.


@node \linebreak & \nolinebreak
@section @code{\linebreak} & @code{\nolinebreak}

@findex \linebreak
@findex \nolinebreak
@cindex line breaks, forcing
@cindex line breaks, preventing

Synopses, one of:

@example
\linebreak
\linebreak[@var{zero-to-four}]
@end example

@noindent
or one of these.

@example
\nolinebreak
\nolinebreak[@var{zero-to-four}]
@end example

Encourage or discourage a line break.  The optional @var{zero-to-four}
is an integer that allows you to soften the instruction.  The default is
4, so that without the optional argument these commands entirely force
or prevent the break.  But for instance, @code{\nolinebreak[1]} is a
suggestion that another place may be better.  The higher the number, the
more insistent the request.  Both commands are fragile
(@pxref{\protect}).

Here we tell @LaTeX{} that a good place to put a linebreak is after the
standard legal text.

@example
\boilerplatelegal@{@} \linebreak[2]
We especially encourage applications from members of traditionally
underrepresented groups.
@end example

When you issue @code{\linebreak}, the spaces in the line are stretched
out so that it extends to the right margin.  @xref{\\}
and@tie{}@ref{\newline} to have the spaces not stretched out.



@node Page breaking
@chapter Page breaking

@cindex page breaking
@cindex breaking pages

Ordinarily @LaTeX{} automatically takes care of breaking output into
pages with its usual aplomb.  But if you are writing commands, or
tweaking the final version of a document, then you may need to
understand how to influence its actions.

@c credit: H Vogt https://tex.stackexchange.com/a/115563
@LaTeX{}'s algorithm for splitting a document into pages is more complex
than just waiting until there is enough material to fill a page and
outputting the result.  Instead, @LaTeX{} typesets more material than
would fit on the page and then chooses a break that is optimal in some
way (it has the smallest badness). An example of the advantage of this
approach is that if the page has some vertical space that can be
stretched or shrunk, such as with rubber lengths between paragraphs,
then @LaTeX{} can use that to avoid widow lines (where a new page starts
with the last line of a paragraph; @LaTeX{} can squeeze the extra line
onto the first page) and orphans (where the first line of paragraph is
at the end of a page; @LaTeX{} can stretch the material of the first
page so the extra line falls on the second page). Another example is
where @LaTeX{} uses available vertical shrinkage to fit on a page not
just the header for a new section but also the first two lines of that
section.

But @LaTeX{} does not optimize over the entire document's set of page
breaks. So it can happen that the first page break is great but the
second one is lousy; to break the current page @LaTeX{} doesn't look as
far ahead as the next page break.  So occasionally you may want to
influence page breaks while preparing a final version of a document.

@xref{Layout} for more material that is relevant to page breaking.

@menu
* \clearpage & \cleardoublepage::   Start a new page; eject floats.
* \newpage::                        Start a new page.
* \enlargethispage::                Enlarge the current page a bit.
* \pagebreak & \nopagebreak::       Forcing & avoiding page breaks.
@end menu


@node \clearpage & \cleardoublepage
@section @code{\clearpage} & @code{\cleardoublepage} 

@findex \clearpage
@cindex flushing floats and starting a page
@cindex starting a new page and clearing floats
@findex \cleardoublepage
@cindex starting on a right-hand page

Synopsis:

@example
\clearpage
@end example

@noindent
or

@example
\cleardoublepage
@end example

End the current page and output all of the pending floating figures and
tables (@pxref{Floats}).  If there are too many floats to fit on the
page then @LaTeX{} will put in extra pages containing only floats.  In
two-sided printing, @code{\cleardoublepage} also makes the next page of
content a right-hand page, an odd-numbered page, if necessary inserting
a blank page.  The @code{\clearpage} command is robust while
@code{\cleardoublepage} is fragile (@pxref{\protect}).

@LaTeX{}'s page breaks are optimized so ordinarily you only use this
command in a document body to polish the final version, or inside
commands.

@c credit: https://www.tex.ac.uk/FAQ-reallyblank.html
The @code{\cleardoublepage} command will put in a blank page, but it
will have the running headers and footers.  To get a really blank
page, use this command.

@example
\let\origdoublepage\cleardoublepage
\newcommand@{\clearemptydoublepage@}@{%
  \clearpage
  @{\pagestyle@{empty@}\origdoublepage@}%
@}
@end example

@noindent
If you want @LaTeX{}'s standard @code{\chapter} command to do this then
add the line @code{\let\cleardoublepage\clearemptydoublepage}.

The command @code{\newpage} (@pxref{\newpage}) also ends the current
page, but without clearing pending floats.  And, if @LaTeX{} is in
two-column mode then @code{\newpage} ends the current column while
@code{\clearpage} and @code{\cleardoublepage} end the current page.



@node \newpage
@section @code{\newpage}

@findex \newpage
@cindex new page, starting
@cindex starting a new page

Synopsis:

@example
\newpage
@end example

End the current page.  This command is robust (@pxref{\protect}).

@LaTeX{}'s page breaks are optimized so ordinarily you only use this
command in a document body to polish the final version, or inside
commands.

While the commands @code{\clearpage} and @code{\cleardoublepage} also
end the current page, in addition they clear pending floats
(@pxref{\clearpage & \cleardoublepage}).  And, if @LaTeX{} is in
two-column mode then @code{\clearpage} and @code{\cleardoublepage} end
the current page, possibly leaving an empty column, while
@code{\newpage} only ends the current column.

In contrast with @code{\pagebreak} (@pxref{\pagebreak & \nopagebreak}),
the @code{\newpage} command will cause the new page to start right where
requested.  This

@example
Four score and seven years ago our fathers brought forth on this
continent,
\newpage
\noindent a new nation, conceived in Liberty, and dedicated to the
proposition that all men are created equal.
@end example

@noindent
makes a new page start after @samp{continent,} and the cut-off line is
not right justified.  In addition, @code{\newpage} does not vertically
stretch out the page, as @code{\pagebreak} does.


@node \enlargethispage
@section @code{\enlargethispage}

@findex \enlargethispage
@cindex enlarge current page

Synopsis, one of:

@example
\enlargethispage@{size@}
\enlargethispage*@{size@}
@end example

Enlarge the @code{\textheight} for the current page.  The required
argument @var{size} must be a rigid length (@pxref{Lengths}).  It may be
positive or negative.  This command is fragile (@pxref{\protect}).

A common strategy is to wait until you have the final text of a
document, and then pass through it tweaking line and page breaks.  This
command allows you some page size leeway.

This will allow one extra line on the current page.

@example
\enlargethispage@{\baselineskip@}
@end example

The starred form @code{\enlargesthispage*} tries to squeeze the material
together on the page as much as possible, for the common use case of
getting one more line on the page. This is often used together with an
explicit @code{\pagebreak}.


@node \pagebreak & \nopagebreak
@section @code{\pagebreak} & @code{\nopagebreak}

@findex \pagebreak
@findex \nopagebreak
@cindex page break, forcing
@cindex page break, preventing

Synopses:

@example
\pagebreak
\pagebreak[@var{zero-to-four}]
@end example

@noindent
or

@example
\nopagebreak
\nopagebreak[@var{zero-to-four}]
@end example

Encourage or discourage a page break.  The optional @var{zero-to-four}
is an integer that allows you to soften the request. The default is 4,
so that without the optional argument these commands entirely force or
prevent the break.  But for instance @code{\nopagebreak[1]} suggests to
@LaTeX{} that another spot might be preferable.  The higher the number,
the more insistent the request.  Both commands are fragile
(@pxref{\protect}).

@LaTeX{}'s page endings are optimized so ordinarily you only use this
command in a document body to polish the final version, or inside
commands.

If you use these inside a paragraph, they apply to the point following
the line in which they appear.  So this

@example
Four score and seven years ago our fathers brought forth on this
continent,
\pagebreak
a new nation, conceived in Liberty, and dedicated to the proposition
that all men are created equal.
@end example

@noindent
does not give a page break at @samp{continent,} but instead at
@samp{nation,} since that is where @LaTeX{} breaks that line.  In
addition, with @code{\pagebreak} the vertical space on the page is
stretched out where possible so that it extends to the normal bottom
margin.  This can look strange, and if @code{\flushbottom} is in effect
this can cause you to get @samp{Underfull \vbox (badness 10000) has
occurred while \output is active}.  @xref{\newpage} for a command that
does not have these effects.


@node Footnotes
@chapter Footnotes

@cindex footnotes, creating

Place a footnote at the bottom of the current page, as here.

@example
No@"{e}l Coward quipped that having to read a footnote is like having
to go downstairs to answer the door, while in the midst of making
love.\footnote@{%
  I wouldn't know, I don't read footnotes.@}
@end example

You can put multiple footnotes on a page. If the footnote text becomes
too long then it will flow to the next page.

You can also produce footnotes by combining the @code{\footnotemark} and
the @code{\footnotetext} commands, which is useful in special
circumstances.

To make bibliographic references come out as footnotes you need to
include a bibliographic style with that behavior (@pxref{Using BibTeX}).

@menu
* \footnote::                Insert a footnote.
* \footnotemark::            Insert footnote mark only.
* \footnotetext::            Insert footnote text only.
* Footnotes in section headings::     Chapter or section titles.  
* Footnotes in a table::     Table footnotes.  
* Footnotes of footnotes::   Multiple classes of footnotes.  
@end menu


@node \footnote
@section @code{\footnote}

@findex \footnote

Synopsis, one of:

@example
\footnote@{@var{text}@}
\footnote[@var{number}]@{@var{text}@}
@end example

Place a footnote @var{text} at the bottom of the current page.

@example
There are over a thousand footnotes in Gibbon's 
\textit@{Decline and Fall of the Roman Empire@}.\footnote@{%
  After reading an early version with endnotes David Hume complained, 
  ``One is also plagued with his Notes, according to the present Method 
  of printing the Book'' and suggested that they ``only to be printed 
  at the Margin or the Bottom of the Page.''@}
@end example

The optional argument @var{number} allows you to specify the number of
the footnote.  If you use this then @LaTeX{} does not increment the
@code{footnote} counter.

@cindex footnotes, symbols instead of numbers
@findex \fnsymbol@r{, and footnotes}
@findex \@@fnsymbol
By default, @LaTeX{} uses arabic numbers as footnote markers.  Change
this with something like
@code{\renewcommand@{\thefootnote@}@{\fnsymbol@{footnote@}@}}, which
uses a sequence of symbols (@pxref{\alph \Alph \arabic \roman \Roman
\fnsymbol}).  To make this change global put that in the preamble.  If
you make the change local then you may want to reset the counter with
@code{\setcounter@{footnote@}@{0@}}.

@LaTeX{} determines the spacing of footnotes with two parameters.

@cindex footnote parameters
@cindex parameters, for footnotes

@ftable @code
@item \footnoterule
@anchor{footnote footnoterule}
Produces the rule separating the main text on a page from the page's
footnotes.  Default dimensions in the standard document classes (except
@code{slides}, where it does not appear) is: vertical thickness of
@code{0.4pt}, and horizontal size of @code{0.4\columnwidth} long.
Change the rule with something like this.

@c Credit egreg: https://tex.stackexchange.com/a/21917
@example
\renewcommand@{\footnoterule@}@{% Kerns avoid vertical space
  \kern -3pt                         % This -3 is negative
  \hrule width \textwidth height 1pt % of the sum of this 1
  \kern 2pt@}                         % and this 2
@end example

@item \footnotesep
@anchor{footnote footnotesep}
The height of the strut placed at the beginning of the footnote
(@pxref{\strut}).  By default, this is set to the normal strut for
@code{\footnotesize} fonts (@pxref{Font sizes}), therefore there is no
extra space between footnotes.  This is @samp{6.65pt} for @samp{10pt},
@samp{7.7pt} for @samp{11pt}, and @samp{8.4pt} for @samp{12pt}.  Change
it as with @code{\setlength@{\footnotesep@}@{11pt@}}.

@end ftable

The @code{\footnote} command is fragile (@pxref{\protect}).

@LaTeX{}'s default puts many restrictions on where you can use a
@code{\footnote}; for instance, you cannot use it in an argument to a
sectioning command such as @code{\chapter} (it can only be used in outer
paragraph mode; @pxref{Modes}).  There are some workarounds; see
following sections.

@cindex Footnotes, in a minipage
@cindex mpfootnote counter
In a @code{minipage} environment the @code{\footnote} command uses the
@code{mpfootnote} counter instead of the @code{footnote} counter, so
they are numbered independently.  They are shown at the bottom of the
environment, not at the bottom of the page.  And by default they are
shown alphabetically. @xref{minipage} and @ref{Footnotes in a table}.


@node \footnotemark
@section @code{\footnotemark}

@findex \footnotemark

Synopsis, one of:

@example
\footnotemark
\footnotemark[@var{number}]
@end example

Put the current footnote mark in the text. To specify associated text
for the footnote see@tie{}@ref{\footnotetext}.  The optional argument
@var{number} causes the command to use that number to determine the
footnote mark. This command can be used in inner paragraph mode
(@pxref{Modes}).

If you use @code{\footnotemark} without the optional argument then it
increments the footnote counter but if you use the optional @var{number}
then it does not. The next example produces several consecutive footnote
markers referring to the same footnote.

@example
The first theorem\footnote@{Due to Gauss.@} 
and the second theorem\footnotemark[\value@{footnote@}] 
and the third theorem.\footnotemark[\value@{footnote@}]
@end example

If there are intervening footnotes then you must remember the value of the
common mark.  This example gives the same institutional affiliation to
both the first and third authors (@code{\thanks} is a version of
@code{footnote}), by-hand giving the number of the footnote.

@example
\title@{A Treatise on the Binomial Theorem@}
\author@{J Moriarty\thanks@{University of Leeds@} 
  \and A C Doyle\thanks@{Durham University@} 
  \and S Holmes\footnotemark[1]@}
\begin@{document@}
\maketitle
@end example 

This uses a counter to remember the footnote number.  The third sentence
is followed by the same footnote marker as the first.

@example
\newcounter@{footnoteValueSaver@}
All babies are illogical.\footnote@{%
  Lewis Carroll.@}\setcounter@{footnoteValueSaver@}@{\value@{footnote@}@}
Nobody is despised who can manage a crocodile.\footnote@{%
  Captain Hook.@}
Illogical persons are despised.\footnotemark[\value@{footnoteValueSaver@}]
Therefore, anyone who can manage a crocodile is not a baby.
@end example

@PkgIndex{cleveref}
@PkgIndex{hyperref}
This example accomplishes the same by using the package @file{cleveref}.

@c from SE user Jake http://tex.stackexchange.com/a/10116/339
@example
\usepackage@{cleveref@}[2012/02/15]   % in preamble 
\crefformat@{footnote@}@{#2\footnotemark[#1]#3@}
...
The theorem is from Evers.\footnote@{\label@{fn:TE@}Tinker, Evers, 1994.@}
The corollary is from Chance.\footnote@{Evers, Chance, 1990.@}
But the key lemma is from Tinker.\cref@{fn:TE@}
@end example

@PkgIndex{hyperref}
It will work with the package @file{hyperref}.


@node \footnotetext
@section @code{\footnotetext}

@findex \footnotetext

Synopsis, one of:

@example
\footnotetext@{@var{text}@}
\footnotetext[@var{number}]@{@var{text}@}
@end example

Place @var{text} at the bottom of the page as a footnote.  It pairs with
@code{\footnotemark} (@pxref{\footnotemark}) and can come anywhere after
that command, but must appear in outer paragraph mode (@pxref{Modes}).
The optional argument @var{number} changes the number of the footnote
mark.

@xref{\footnotemark} and@tie{}@ref{Footnotes in a table} for usage
examples.


@node Footnotes in section headings
@section Footnotes in section headings

@cindex footnote, in section headings
@cindex table of contents, avoiding footnotes

Putting a footnote in a section heading, as in:

@example
\section@{Full sets\protect\footnote@{This material due to ...@}@}
@end example

@noindent
causes the footnote to appear at the bottom of the page where the
section starts, as usual, but also at the bottom of the table of
contents, where it is not likely to be desired.  The simplest way
to have it not appear on the table of contents is to use the optional
argument to @code{\section}

@example
\section[Please]@{Please\footnote@{%
  Don't footnote in chapter and section headers!@}@}
@end example

@noindent
No @code{\protect} is needed in front of @code{\footnote} here because
what gets moved to the table of contents is the optional argument.


@node Footnotes in a table
@section Footnotes in a table

@cindex footnote, in a table

Inside a @code{tabular} or @code{array} environment the @code{\footnote}
command does not work; there is a footnote mark in the table cell but
the footnote text does not appear.  The solution is to use a
@code{minipage} environment as here (@pxref{minipage}).

@example
\begin@{center@}
  \begin@{minipage@}@{\textwidth@} \centering
     \begin@{tabular@}@{l|l@}
       \textsc@{Ship@}           &\textsc@{Book@} \\ \hline 
       \textit@{HMS Sophie@}     &Master and Commander  \\ 
       \textit@{HMS Polychrest@} &Post Captain  \\  
       \textit@{HMS Lively@}     &Post Captain \\
       \textit@{HMS Surprise@}   &A number of books\footnote@{%
                                  Starting with HMS Surprise.@}
     \end@{tabular@}
  \end@{minipage@}                              
\end@{center@}
@end example

Inside a @code{minipage}, footnote marks are lowercase letters.  Change
that with something like
@code{\renewcommand@{\thempfootnote@}@{\arabic@{mpfootnote@}@}}
(@pxref{\alph \Alph \arabic \roman \Roman \fnsymbol}).

The footnotes in the prior example appear at the bottom of the
@code{minipage}.  To have them appear at the bottom of the main page, as
part of the regular footnote sequence, use the @code{\footnotemark} and
@code{\footnotetext} pair and make a new counter.

@example
\newcounter@{mpFootnoteValueSaver@}
\begin@{center@}
  \begin@{minipage@}@{\textwidth@}
    \setcounter@{mpFootnoteValueSaver@}@{\value@{footnote@}@} \centering
     \begin@{tabular@}@{l|l@}
       \textsc@{Woman@}             &\textsc@{Relationship@} \\ \hline 
       Mona                       &Attached\footnotemark  \\ 
       Diana Villiers             &Eventual wife  \\  
       Christine Hatherleigh Wood &Fiance\footnotemark 
     \end@{tabular@}
  \end@{minipage@}%  percent sign keeps footnote text close to minipage
  \stepcounter@{mpFootnoteValueSaver@}%
    \footnotetext[\value@{mpFootnoteValueSaver@}]@{%
      Little is known other than her death.@}%
  \stepcounter@{mpFootnoteValueSaver@}%
    \footnotetext[\value@{mpFootnoteValueSaver@}]@{%
      Relationship is unresolved in XXI.@}
\end@{center@}
@end example

For a floating @code{table} environment (@pxref{table}), use the
@file{tablefootnote} package.

@example
\usepackage@{tablefootnote@}  % in preamble
   ...
\begin@{table@}
  \centering
     \begin@{tabular@}@{l|l@}
     \textsc@{Date@}  &\textsc@{Campaign@} \\ \hline 
     1862           &Fort Donelson \\ 
     1863           &Vicksburg     \\  
     1865           &Army of Northern Virginia\tablefootnote@{%
                      Ending the war.@}
     \end@{tabular@}
    \caption@{Forces captured by US Grant@}
\end@{table@}
@end example

@noindent
The footnote appears at the page bottom and is numbered in sequence with
other footnotes.


@node Footnotes of footnotes
@section Footnotes of footnotes

@cindex footnote, of a footnote

@PkgIndex{bigfoot}
Particularly in the humanities, authors can have multiple classes of
footnotes, including having footnotes of footnotes.  The package
@file{bigfoot} extends @LaTeX{}'s default footnote mechanism in many
ways, including allow these two, as in this example.

@example
\usepackage@{bigfoot@}    % in preamble
\DeclareNewFootnote@{Default@}
\DeclareNewFootnote@{from@}[alph]   % create class \footnotefrom@{@}
 ...
The third theorem is a partial converse of the 
second.\footnotefrom@{%
  First noted in Wilson.\footnote@{Second edition only.@}@}
@end example


@node Definitions
@chapter Definitions

@cindex definitions

@LaTeX{} has support for making new commands of many different kinds.

@menu
* \newcommand & \renewcommand::    (Re)define a new command.
* \providecommand::                Define a new command, if name not used.
* \makeatletter & \makeatother::   Change the status of the at-sign character.
* \@@ifstar::                      Define your own commands with *-variants.
* \newcounter::                    Define a new counter.
* \newlength::                     Define a new length.
* \newsavebox::                    Define a new box.
* \newenvironment & \renewenvironment::   Define a new environment.
* \newtheorem::                    Define a new theorem-like environment.
* \newfont::                       Define a new font name.
* \protect::                       Using tricky commands.
* \ignorespaces & \ignorespacesafterend:: Discard extra spaces.
@end menu


@node \newcommand & \renewcommand
@section @code{\newcommand} & @code{\renewcommand}

@findex \newcommand
@cindex commands, defining new ones
@cindex commands, redefining
@cindex defining a new command
@cindex new commands, defining

Synopses, one of:

@example
\newcommand@{\@var{cmd}@}@{@var{defn}@}
\newcommand@{\@var{cmd}@}[@var{nargs}]@{@var{defn}@}
\newcommand@{\@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
\newcommand*@{\@var{cmd}@}@{@var{defn}@}
\newcommand*@{\@var{cmd}@}[@var{nargs}]@{@var{defn}@}
\newcommand*@{\@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
@end example

@noindent
or one of these.

@example
\renewcommand@{\@var{cmd}@}[@var{nargs}]@{@var{defn}@}
\renewcommand@{\@var{cmd}@}[@var{nargs}]@{@var{defn}@}
\renewcommand@{\@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
\renewcommand*@{\@var{cmd}@}@{@var{defn}@}
\renewcommand*@{\@var{cmd}@}[@var{nargs}]@{@var{defn}@}
\renewcommand*@{\@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
@end example

Define or redefine a command.  See also the discussion of
@code{\DeclareRobustCommand} in @ref{Class and package commands}.
@cindex starred form, defining new commands
@cindex *-form, defining new commands
The starred form of these two requires that the arguments not contain
multiple paragraphs of text (in plain @TeX{} terms that it not be
@code{\long}).

These are the parameters:

@table @var
@item cmd

Required; the command name.  It must begin with a backslash, @code{\},
and must not begin with the four letter string @code{\end}.  For
@code{\newcommand}, it must not be already defined.  For
@code{\renewcommand}, this name must already be defined.

@item nargs
Optional; an integer from 0 to 9, specifying the number of arguments
that the command takes, including any optional argument.  Omitting this
argument is the same as specifying 0, meaning that the command has no
arguments.  If you redefine a command, the new version can have a
different number of arguments than the old version.

@item optargdefault
Optional; if this argument is present then the first argument of
@code{\@var{cmd}} is optional, with default value @var{optargdefault}
(which may be the empty string).  If this argument is not present then
@code{\@var{cmd}} does not take an optional argument.

@cindex positional parameter
That is, if @code{\@var{cmd}} is used with square brackets, as in
@code{\@var{cmd}[@var{optval}]@{...@}...}, then within @var{defn} the
parameter@tie{}@code{#1} is set to the value of @var{optval}.  On the
other hand, if @code{\@var{cmd}} is called without the square brackets
then within @var{defn} the parameter @code{#1} is set to the value of
@var{optargdefault}.  In either case, the required arguments start with
@code{#2}.

Omitting @code{[@var{optargdefault}]} is different from having the
square brackets with no contents, as in @code{[]}.  The former sets
@code{#1} to the value of @var{optargdefault}; the latter sets @code{#1}
to the empty string.

@item defn
Required; the text to be substituted for every occurrence of
@code{\@var{cmd}}. The parameters @code{#1}, @code{#2},
... @code{#@var{nargs}} are replaced by the values that you supply when
you call the command (or by the default value if there is an optional
argument and you don't exercise the option).

@end table

@TeX{} ignores spaces in the source following an alphabetic control
sequence, as in @samp{\cmd }.  If you actually want a space there, one
solution is to type @code{@{@}} after the command (@samp{\cmd@{@} }, and
another solution is to use an explicit control space (@samp{\cmd\ }).

A simple example of defining a new command:
@code{\newcommand@{\RS@}@{Robin Smith@}} results in @code{\RS} being
replaced by the longer text.  Redefining an existing command is similar:
@code{\renewcommand@{\qedsymbol@}@{@{\small QED@}@}}.

If you try to define a command and the name has already been used then
you get something like @samp{LaTeX Error: Command \fred already
defined. Or name \end... illegal, see p.192 of the manual}.  If you try
to redefine a command and the name has not yet been used then you get
something like @samp{LaTeX Error: \hank undefined}.

Here the first command definition has no arguments, and the second has
one required argument.

@example
\newcommand@{\student@}@{Ms~O'Leary@}
\newcommand@{\defref@}[1]@{Definition~\ref@{#1@}@}
@end example

@noindent
Use the first as in @code{I highly recommend \student@{@} to you}.  The
second has a variable, so that @code{\defref@{def:basis@}} expands to
@code{Definition~\ref@{def:basis@}}, which ultimately expands to
something like @samp{Definition~3.14}.

Similarly, but with two required arguments:
@code{\newcommand@{\nbym@}[2]@{$#1 \times #2$@}} is invoked as
@code{\nbym@{2@}@{k@}}.

This example has an optional argument.

@example
\newcommand@{\salutation@}[1][Sir or Madam]@{Dear #1:@}
@end example

@noindent
Then @code{\salutation} gives @samp{Dear Sir or Madam:} while
@code{\salutation[John]} gives @samp{Dear John:}.  And
@code{\salutation[]} gives @samp{Dear :}.

This example has an optional argument and two required arguments.

@example
\newcommand@{\lawyers@}[3][company]@{#2, #3, and~#1@}
I employ \lawyers[Howe]@{Dewey@}@{Cheatem@}.
@end example

@noindent
The output is @samp{I employ Dewey, Cheatem, and Howe}.  The optional
argument, the @code{Howe}, is associated with @code{#1}, while
@code{Dewey} and @code{Cheatem} are associated with @code{#2}
and@tie{}@code{#3}.  Because of the optional argument,
@code{\lawyers@{Dewey@}@{Cheatem@}} will give the output @samp{I employ
Dewey, Cheatem, and company}.

The braces around @var{defn} do not define a group, that is, they do not
delimit the scope of the result of expanding @var{defn}.  For example,
with @code{\newcommand@{\shipname@}[1]@{\it #1@}}, in this sentence,

@example
The \shipname@{Monitor@} met the \shipname@{Merrimac@}.
@end example

@noindent
the words @samp{met the} would incorrectly be in italics.  The solution
is to put another pair of braces inside the definition:
@code{\newcommand@{\shipname@}[1]@{@{\it #1@}@}}.


@node \providecommand 
@section @code{\providecommand}

@findex \providecommand
@cindex commands, defining new ones
@cindex defining a new command
@cindex new commands, defining

Synopses, one of:

@example
\providecommand@{@var{cmd}@}@{@var{defn}@}
\providecommand@{@var{cmd}@}[@var{nargs}]@{@var{defn}@}
\providecommand@{@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
\providecommand*@{@var{cmd}@}@{@var{defn}@}
\providecommand*@{@var{cmd}@}[@var{nargs}]@{@var{defn}@}
\providecommand*@{@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
@end example

Defines a command, as long as no command of this name already exists.
If no command of this name already exists then this has the same effect
as @code{\newcommand}.  If a command of this name already exists then
this definition does nothing.  This is particularly useful in a file
that may be loaded more than once, such as a style file.
@xref{\newcommand & \renewcommand} for the description of the arguments.

This example

@example
\providecommand@{\myaffiliation@}@{Saint Michael's College@}
\providecommand@{\myaffiliation@}@{Saint Michael's College@}
From \myaffiliation.
@end example

@noindent
outputs @samp{From Saint Michael's College}.  Unlike @code{\newcommand},
the repeated use of @code{\providecommand} does not give an error.


@node \makeatletter & \makeatother
@section @code{\makeatletter} & @code{\makeatother}

Synopsis:

@example
\makeatletter
  ... definition of commands with @@ in their name ..
\makeatother
@end example

Use this pair when you redefine @LaTeX{} commands that are named with an
at-sign character@tie{}@samp{@code{@@}}.  The @code{\makeatletter}
declaration makes the at-sign character have the category code of a
letter, code@tie{}11.  The @code{\makeatother} declaration sets the
category code of the at-sign to code@tie{}12, its default value.

As @TeX{} reads characters, it assigns each one a category code, or
@cindex catcode
@cindex character category code
@cindex category code, character
@dfn{catcode}. For instance, it assigns the backslash
character@tie{}@samp{@code{\}} the catcode@tie{}0.  Command names
consist of a category@tie{}0 character, ordinarily backslash, followed
by letters, category@tie{}11 characters (except that a command name can
also consist of a category@tie{}0 character followed by a single
non-letter symbol).

@LaTeX{}'s source code has the convention that some commands use
@code{@@} in their name.  These commands are mainly intended for package
or class writers.  The convention prevents authors who are just using a
package or class from accidentally replacing such a command with one of
their own, because by default the at-sign has catcode@tie{}12.

The pair @code{\makeatletter} and @code{\makeatother} changes the
default code and then changes it back.  Use them inside a @file{.tex}
file, in the preamble, when you are defining or redefining commands
named with @code{@@}, by having them surround your definition.  Don't
use these inside @file{.sty} or @file{.cls} files since the
@code{\usepackage} and @code{\documentclass} commands already arrange
that the at-sign has the character code of a letter, catcode@tie{}11.

@PkgIndex{macros2e}
For a comprehensive list of macros with an at-sign in their names see
@url{http://ctan.org/pkg/macros2e}.

In this example the class file has a command
@code{\thesis@@universityname} that the user wants to change.  These
three lines should go in the preamble, before the
@code{\begin@{document@}}.

@example
\makeatletter
\renewcommand@{\thesis@@universityname@}@{Saint Michael's College@}
\makeatother
@end example


@node \@@ifstar
@section @code{\@@ifstar}

@findex \@@ifstar
@cindex commands, star-variants
@cindex star-variants, commands

Synopsis:

@example
\newcommand@{\mycmd@}@{\@@ifstar@{\mycmd@@star@}@{\mycmd@@nostar@}@}
\newcommand@{\mycmd@@nostar@}[@var{nostar-num-args}]@{@var{nostar-body}@} 
\newcommand@{\mycmd@@star@}[@var{star-num-args}]@{@var{star-body}@}
@end example

Many standard @LaTeX{} environments or commands have a variant with the
same name but ending with a star character@tie{}@code{*}, an asterisk.
Examples are the @code{table} and @code{table*} environments and the
@code{\section} and @code{\section*} commands.

When defining environments, following this pattern is straightforward
because @code{\newenvironment} and @code{\renewenvironment} allow the
environment name to contain a star.  For commands the situation is more
complex.  As in the synopsis above, there will be a user-called command,
given above as @code{\mycmd}, which peeks ahead to see if it is followed
by a star.  For instance, @LaTeX{} does not really have a
@code{\section*} command; instead, the @code{\section} command peeks
ahead.  This command does not accept arguments but instead expands to
one of two commands that do accept arguments.  In the synopsis these two
are @code{\mycmd@@nostar} and @code{\mycmd@@star}.  They could take the
same number of arguments or a different number, or no arguments at all.
As always, in a @LaTeX{} document a command using at-sign@tie{}@code{@@}
must be enclosed inside a @code{\makeatletter ... \makeatother} block
(@pxref{\makeatletter & \makeatother}).

This example of @code{\@@ifstar} defines the command @code{\ciel} and a
variant @code{\ciel*}.  Both have one required argument.  A call to
@code{\ciel@{night@}} will return "starry night sky" while
@code{\ciel*@{blue@}} will return "starry not blue sky".

@example
\newcommand*@{\ciel@@unstarred@}[1]@{starry #1 sky@}
\newcommand*@{\ciel@@starred@}[1]@{starry not #1 sky@}
\newcommand*@{\ciel@}@{\@@ifstar@{\ciel@@starred@}@{\ciel@@unstarred@}@}
@end example

In the next example, the starred variant takes a different number of
arguments than the unstarred one.  With this definition, Agent 007's
@code{``My name is \agentsecret*@{Bond@},
\agentsecret@{James@}@{Bond@}.''} is equivalent to entering the commands
@code{``My name is \textsc@{Bond@}, \textit@{James@} textsc@{Bond@}.''}

@example
\newcommand*@{\agentsecret@@unstarred@}[2]@{\textit@{#1@} \textsc@{#2@}@}
\newcommand*@{\agentsecret@@starred@}[1]@{\textsc@{#1@}@}
\newcommand*@{\agentsecret@}@{%
  \@@ifstar@{\agentsecret@@starred@}@{\agentsecret@@unstarred@}@}
@end example

There are two sometimes more convenient ways to accomplish the work of
@code{\@@ifstar}.  The @file{suffix} package allows the construct
@code{\newcommand\mycommand@{@var{unstarred version}@}} followed by
@code{\WithSuffix\newcommand\mycommand*@{@var{starred version}@}}.  And
@LaTeX{}3 has the @file{xparse} package that allows this code.

@example
\NewDocumentCommand\foo@{s@}@{\IfBooleanTF#1
  @{@var{starred version}@}%
  @{@var{unstarred version}@}% 
  @}
@end example


@node \newcounter
@section @code{\newcounter}: Allocating a counter

@findex \newcounter
@cindex counters, defining new

Synopsis, one of:

@example
\newcounter@{@var{countername}@}
\newcounter@{@var{countername}@}[@var{supercounter}]
@end example

Globally defines a new counter named @var{countername} and initialize it
to zero (@pxref{Counters}).

The name @var{countername} must consist of letters only. It does not
begin with a backslash.  This name must not already be in use by another
counter.

When you use the optional argument @code{[@var{supercounter}]} then the
counter @var{countername} will be reset to zero whenever
@var{supercounter} is incremented.  For example, ordinarily
@code{subsection} is numbered within @code{section} so that any time you
increment @var{section}, either with @code{\stepcounter}
(@pxref{\stepcounter}) or @code{\refstepcounter}
(@pxref{\refstepcounter}), then @LaTeX{} will reset @var{subsection} to
zero.

This example

@example
\newcounter@{asuper@}  \setcounter@{asuper@}@{1@}
\newcounter@{asub@}[asuper] \setcounter@{asub@}@{3@}   % Note `asuper'
The value of asuper is \arabic@{asuper@} and of asub is \arabic@{asub@}.
\stepcounter@{asuper@}
Now asuper is \arabic@{asuper@} while asub is \arabic@{asub@}.
@end example

produces @samp{The value of asuper is 1 and that of asub is 3} and
@samp{Now asuper is 2 while asub is 0}.

If the counter already exists, for instance by entering @code{asuper}
twice, then you get something like @samp{LaTeX Error: Command \c@@asuper
already defined.  Or name \end... illegal, see p.192 of the manual.}.

If you use the optional argument then the super counter must already
exist. Entering @code{\newcounter@{jh@}[lh]} when @code{lh} is not a
defined counter will get you @samp{LaTeX Error: No counter 'lh'
defined.}


@node \newlength
@section @code{\newlength}

@findex \newlength
@cindex lengths, allocating new
@cindex rubber lengths, defining new
@cindex skip register, plain @TeX{}
@cindex glue register, plain @TeX{}

Synopsis:

@example
\newlength@{@var{arg}@}
@end example

Allocate a new length register (@pxref{Lengths}).  The required argument
@var{arg} must begin with a backslash, @code{\}.  The new register holds
rubber lengths such as @code{72.27pt} or @code{1in plus.2in minus.1in}
(a @LaTeX{} length register is what plain @TeX{} calls a @code{skip}
register).  The initial value is zero.  The control sequence
@code{\@var{arg}} must not be already defined.

An example:

@example
\newlength@{\graphichgt@}
@end example

If you forget the backslash then you get @samp{Missing control sequence
inserted}.  If the command sequence already exists then you get
something like @samp{LaTeX Error: Command \graphichgt already defined.
Or name \end... illegal, see p.192 of the manual}.


@node \newsavebox
@section @code{\newsavebox}

@findex \newsavebox
@cindex box, allocating new

Synopsis:

@example
\newsavebox@{\@var{cmd}@}
@end example

Define \@var{cmd}, the string consisting of a backslash followed by
@var{cmd}, to refer to a new bin for storing material.  These bins hold
material that has been typeset, to use multiple times or to measure or
manipulate (@pxref{Boxes}).  The bin name \@var{cmd} is required, must
start with a backslash, \, and must not already be a defined command.
This command is fragile (@pxref{\protect}).

This allocates a bin and then puts typeset material into it.

@example
\newsavebox@{\logobox@}
\savebox@{\logobox@}@{LoGo@}
Our logo is \usebox@{\logobox@}. 
@end example

@noindent
The output is @samp{Our logo is LoGo}.

If there is an already defined bin then you get something like
@samp{LaTeX Error: Command \logobox already defined. Or name
\end... illegal, see p.192 of the manual}.

The allocation of a box is global.


@node \newenvironment & \renewenvironment
@section @code{\newenvironment} & @code{\renewenvironment}

@findex \newenvironment
@findex \renewenvironment
@cindex environments, defining
@cindex defining new environments
@cindex redefining environments

Synopses, one of:

@example
\newenvironment@{@var{env}@}@{@var{begdef}@}@{@var{enddef}@}
\newenvironment@{@var{env}@}[@var{nargs}]@{@var{begdef}@}@{@var{enddef}@}
\newenvironment@{@var{env}@}[@var{nargs}][@var{optargdefault}]@{@var{begdef}@}@{@var{enddef}@}
\newenvironment*@{@var{env}@}@{@var{begdef}@}@{@var{enddef}@}
\newenvironment*@{@var{env}@}[@var{nargs}]@{@var{begdef}@}@{@var{enddef}@}
\newenvironment*@{@var{env}@}[@var{nargs}][@var{optargdefault}]@{@var{begdef}@}@{@var{enddef}@}
@end example

@noindent
or one of these.

@example
\renewenvironment@{@var{env}@}@{@var{begdef}@}@{@var{enddef}@}
\renewenvironment@{@var{env}@}[@var{nargs}]@{@var{begdef}@}@{@var{enddef}@}
\renewenvironment@{@var{env}@}[@var{nargs}][@var{optargdefault}]@{@var{begdef}@}@{@var{enddef}@}
\renewenvironment*@{@var{env}@}@{@var{begdef}@}@{@var{enddef}@}
\renewenvironment*@{@var{env}@}[@var{nargs}]@{@var{begdef}@}@{@var{enddef}@}
\renewenvironment*@{@var{env}@}[@var{nargs}][@var{optargdefault}]@{@var{begdef}@}@{@var{enddef}@}
@end example

Define or redefine the environment @var{env}, that is, create the
construct @code{\begin@{@var{env}@} ... @var{body} ... \end@{@var{env}@}}.

@cindex @code{*}-form of environment commands 	 
The starred form of these commands requires that the arguments not
contain multiple paragraphs of text.  However, the body of these
environments can contain multiple paragraphs.

@table @var
@item env
Required; the environment name.  It consists only of letters or the
@code{*} character, and thus does not begin with backslash, @code{\}.
It must not begin with the string @code{end}.  For
@code{\newenvironment}, the name @var{env} must not be the name of an
already existing environment, and also the command @code{\@var{env}}
must be undefined.  For @code{\renewenvironment}, @var{env} must be the
name of an existing environment.

@item nargs
Optional; an integer from 0 to 9 denoting the number of arguments of
that the environment takes.  When you use the environment these
arguments appear after the @code{\begin}, as in
@code{\begin@{@var{env}@}@{@var{arg1}@} ... @{@var{argn}@}}.  Omitting
this is equivalent to setting it to 0; the environment will have no
arguments.  When redefining an environment, the new version can have a
different number of arguments than the old version.

@item optargdefault
Optional; if this is present then the first argument of the defined
environment is optional, with default value @var{optargdefault} (which
may be the empty string).  If this is not in the definition then the
environment does not take an optional argument.

That is, when @var{optargdefault} is present in the definition of the
environment then you can start the environment with square brackets, as
in @code{\begin@{@var{env}@}[@var{optval}]@{...@} ... \end@{@var{env}@}}.
In this case, within @var{begdefn} the parameter @code{#1} is set to the
value of @var{optval}.  If you call @code{\begin@{@var{env}@}} without
square brackets, then within @var{begdefn} the parameter @code{#1} is
set to the value of the default @var{optargdefault}.  In either case,
any required arguments start with @code{#2}.

Omitting @code{[@var{myval}]} in the call is different than having the
square brackets with no contents, as in @code{[]}.  The former results
in @code{#1} expanding to @var{optargdefault}; the latter results in
@code{#1} expanding to the empty string.

@item begdef
Required; the text expanded at every occurrence of
@code{\begin@{@var{env}@}}.  Within @var{begdef}, the parameters
@code{#1}, @code{#2}, ... @code{#@var{nargs}}, are replaced by the
values that you supply when you call the environment; see the examples
below.

@item enddef
Required; the text expanded at every occurrence of
@code{\end@{@var{env}@}}.  This may not contain any parameters, that is,
you cannot use @code{#1}, @code{#2}, etc., here (but see the final
example below).

@end table

All environments, that is to say the @var{begdef} code, the environment
body, and the @var{enddef} code, are processed within a group.  Thus, in
the first example below, the effect of the @code{\small} is limited to
the quote and does not extend to material following the environment.

If you try to define an environment and the name has already been used
then you get something like @samp{LaTeX Error: Command \fred already
defined. Or name \end... illegal, see p.192 of the manual}.  If you try
to redefine an environment and the name has not yet been used then you
get something like @samp{LaTeX Error: Environment hank undefined.}.

This example gives an environment like @LaTeX{}'s @code{quotation}
except that it will be set in smaller type.

@example
\newenvironment@{smallquote@}@{%
  \small\begin@{quotation@}
@}@{%
  \end@{quotation@}
@}
@end example

This has an argument, which is set in boldface at the start of a
paragraph.

@example
\newenvironment@{point@}[1]@{%
  \noindent\textbf@{#1@}
@}@{%
@}
@end example 

This one shows the use of a optional argument; it gives a quotation
environment that cites the author.

@example
\newenvironment@{citequote@}[1][Shakespeare]@{%
  \begin@{quotation@}
  \noindent\textit@{#1@}: 
@}@{%
  \end@{quotation@}
@}
@end example

@noindent
The author's name is optional, and defaults to @samp{Shakespeare}.  In
the document, use the environment like this.

@example
\begin@{citequote@}[Lincoln]
  ...
\end@{citequote@}
@end example

The final example shows how to save the value of an argument to use in 
@var{enddef}, in this case in a box (@pxref{\sbox & \savebox}).

@example
\newsavebox@{\quoteauthor@}
\newenvironment@{citequote@}[1][Shakespeare]@{%
  \sbox\quoteauthor@{#1@}%
  \begin@{quotation@} 
@}@{%
  \hspace@{1em plus 1fill@}---\usebox@{\quoteauthor@}
  \end@{quotation@}
@}
@end example


@node \newtheorem
@section @code{\newtheorem}

@findex \newtheorem
@cindex theorems, defining
@cindex defining new theorems

@cindex theorem-like environment
@cindex environment, theorem-like
Synopses:

@example
\newtheorem@{@var{name}@}@{@var{title}@}
\newtheorem@{@var{name}@}@{@var{title}@}[@var{numbered_within}]
\newtheorem@{@var{name}@}[@var{numbered_like}]@{@var{title}@}
@end example

Define a new theorem-like environment.  You can specify one of
@var{numbered_within} and @var{numbered_like}, or neither, but not both.

The first form, @code{\newtheorem@{@var{name}@}@{@var{title}@}}, creates
an environment that will be labelled with @var{title}; see the first
example below.

The second form,
@code{\newtheorem@{@var{name}@}@{@var{title}@}[@var{numbered_within}]},
creates an environment whose counter is subordinate to the existing
counter @var{numbered_within}, so this counter will be reset when
@var{numbered_within} is reset.  See the second example below.

The third form
@code{\newtheorem@{@var{name}@}[@var{numbered_like}]@{@var{title}@}},
with optional argument between the two required arguments, creates an
environment whose counter will share the previously defined counter
@var{numbered_like}.  See the third example.

This command creates a counter named @var{name}.  In addition, unless
the optional argument @var{numbered_like} is used, inside of the
theorem-like environment the current @code{\ref} value will be that of
@code{\the@var{numbered_within}} (@pxref{\ref}).

This declaration is global.  It is fragile (@pxref{\protect}).

Arguments:

@table @var
@item name
The name of the environment.  It is a string of letters.  It must not
begin with a backslash, @code{\}.  It must not be the name of an
existing environment, and the command name @code{\@var{name}} must not
already be defined.

@item title
The text to be printed at the beginning of the environment, before the
number. For example, @samp{Theorem}.

@item numbered_within
Optional; the name of an already defined counter, usually a sectional
unit such as @code{chapter} or @code{section}.  When the
@var{numbered_within} counter is reset then the @var{name} environment's
counter will also be reset.

If this optional argument is not used then the command
@code{\the@var{name}} is set to @code{\arabic@{@var{name}@}}.

@item numbered_like
Optional; the name of an already defined theorem-like environment. The
new environment will be numbered in sequence with @var{numbered_like}.

@end table

Without any optional arguments the environments are numbered
sequentially.  The example below has a declaration in the preamble that
results in @samp{Definition@tie{}1} and @samp{Definition@tie{}2} in the
output.

@example
\newtheorem@{defn@}@{Definition@}
\begin@{document@}
\section@{...@}
\begin@{defn@}
  First def 
\end@{defn@}

\section@{...@}
\begin@{defn@}
  Second def
\end@{defn@}
@end example

This example has the same document body as the prior one.  But here
@code{\newtheorem}'s optional argument @var{numbered_within} is given as
@code{section}, so the output is like @samp{Definition@tie{}1.1} and
@samp{Definition@tie{}2.1}.

@example
\newtheorem@{defn@}@{Definition@}[section]
\begin@{document@}
\section@{...@}
\begin@{defn@}
  First def 
\end@{defn@}

\section@{...@}
\begin@{defn@}
  Second def
\end@{defn@}
@end example

In the next example there are two declarations in the preamble, the
second of which calls for the new @code{thm} environment to use the same
counter as @code{defn}.  It gives @samp{Definition@tie{}1.1}, followed
by @samp{Theorem@tie{}2.1} and @samp{Definition@tie{}2.2}.

@example
\newtheorem@{defn@}@{Definition@}[section]
\newtheorem@{thm@}[defn]@{Theorem@}
\begin@{document@}
\section@{...@}
\begin@{defn@}
  First def 
\end@{defn@}

\section@{...@}
\begin@{thm@}
  First thm
\end@{thm@}

\begin@{defn@}
  Second def
\end@{defn@}
@end example


@node \newfont
@section @code{\newfont}

@findex \newfont
@cindex fonts, new commands for
@cindex defining new fonts

@c @findex .fd @r{file}
This command is obsolete. This description is here only to help with old
documents.  New documents should define fonts in families through the
New Font Selection Scheme which allows you to, for example, associate a
boldface with a roman (@pxref{Fonts}).
@c This is done either by using
@c @file{.fd} files or through the use of an engine that can access system
@c fonts such as Xe@LaTeX{} (@pxref{@TeX{} engines}).

Synopsis:

@example
\newfont@{\@var{cmd}@}@{@var{font description}@}
@end example

Define a command @code{\@var{cmd}} that will change the current font.
The control sequence must not already be defined. It must begin with a
backslash, @code{\}.

@cindex at clause, in font definitions
@cindex design size, in font definitions
The @var{font description} consists of a @var{fontname} and an optional
@dfn{at clause}.  @LaTeX{} will look on your system for a file named
@file{@var{fontname}.tfm}.  The at clause can have the form either
@code{at @var{dimen}} or @code{scaled @var{factor}}, where a
@var{factor} of @samp{1000} means no scaling.  For @LaTeX{}'s purposes,
all this does is scale all the character and other font dimensions
relative to the font's design size, which is a value defined in the
@file{.tfm} file.

This defines two equivalent fonts and typesets a few characters in each.

@example
\newfont@{\testfontat@}@{cmb10 at 11pt@}
\newfont@{\testfontscaled@}@{cmb10 scaled 1100@}
\testfontat abc
\testfontscaled abc
@end example


@node \protect
@section @code{\protect}

@findex \protect
@cindex fragile commands
@cindex robust commands

All @LaTeX{} commands are either @dfn{fragile} or @dfn{robust}.  A
fragile command can break when it is used in the argument to certain
other commands.  Commands that contain data that @LaTeX{} writes to an
auxiliary file and re-reads later are fragile.  This includes material
that goes into a table of contents, list of figures, list of tables,
etc.  Fragile commands also include line breaks, any command that has an
optional argument, and many more. To prevent such commands from
breaking, one solution is to preceded them with the command
@code{\protect}.

For example, when @LaTeX{} runs the @code{\section@{@var{section
name}@}} command it writes the @var{section name} text to the
@file{.aux} auxiliary file, moving it there for use elsewhere in the
document such as in the table of contents.  Any argument that is
internally expanded by @LaTeX{} without typesetting it directly is
referred to as a 
@cindex moving arguments
@dfn{moving argument}.  A command is fragile if it can
expand during this process into invalid @TeX{} code.  Some examples of
moving arguments are those that appear in the @code{\caption@{...@}}
command (@pxref{figure}), in the @code{\thanks@{...@}} command
(@pxref{\maketitle}), and in @@-expressions in the @code{tabular} and
@code{array} environments (@pxref{tabular}).

If you get strange errors from commands used in moving arguments, try
preceding it with @code{\protect}.  Every fragile commands must be
protected with their own @code{\protect}.  

Although usually a @code{\protect} command doesn't hurt, length
commands are robust and should not be preceded by a @code{\protect}
command. Nor can a @code{\protect} command be used in the argument to
@code{\addtocounter} or @code{\setcounter} command.

In this example the @code{\caption} command gives a mysterious error
about an extra curly brace.  Fix the problem by preceding each
@code{\raisebox} command with @code{\protect}.

@example
\begin@{figure@}
  ...
  \caption@{Company headquarters of A\raisebox@{1pt@}@{B@}\raisebox@{-1pt@}@{C@}@}
\end@{figure@}
@end example

In the next example the @code{\tableofcontents} command gives an error
because the @code{\(..\)} in the section title expands to illegal @TeX{}
in the @file{.toc} file.  You can solve this by changing @code{\(..\)}
to @code{\protect\(..\protect\)}.

@example
\begin@{document@}
\tableofcontents
...
\section@{Einstein's \( e=mc^2 \)@}
...
@end example


@node \ignorespaces & \ignorespacesafterend
@section @code{\ignorespaces & \ignorespacesafterend}

@findex \ignorespaces
@findex \ignorespacesafterend
@cindex spaces, ignore around commands
@cindex commands, ignore spaces

Synopsis:

@example
\ignorespaces
@end example

@noindent
or

@example
\ignorespacesafterend
@end example

Both commands cause @LaTeX{} to ignore spaces after the end of the
command up until the first non-space character.  The first is a command
from Plain @TeX{}, and the second is @LaTeX{}-specific.

The @code{ignorespaces} is often used when defining commands via
@code{\newcommand}, or @code{\newenvironment}, or @code{\def}.  The
example below illustrates.  It allows a user to show the points values
for quiz questions in the margin but it is inconvenient because, as
shown in the @code{enumerate} list, users must not put any space between
the command and the question text.

@example
\newcommand@{\points@}[1]@{\makebox[0pt]@{\makebox[10em][l]@{#1~pts@}@}
\begin@{enumerate@} 
  \item\points@{10@}no extra space output here
  \item\points@{15@} extra space between the number and the `extra'
\end@{enumerate@} 
@end example

@noindent
The solution is to change to this.

@example
\newcommand@{\points@}[1]@{%
  \makebox[0pt]@{\makebox[10em][l]@{#1~pts@}@}\ignorespaces@}
@end example

A second example shows spaces being removed from the front of text.  The
commands below allow a user to uniformly attach a title to names.  But,
as given, if a title accidentally starts with a space then
@code{\fullname} will reproduce that.

@example
\makeatletter
\newcommand@{\honorific@}[1]@{\def\@@honorific@{#1@}@} % remember title
\newcommand@{\fullname@}[1]@{\@@honorific~#1@}       % put title before name
\makeatother
\begin@{tabular@}@{|l|@}
\honorific@{Mr/Ms@}  \fullname@{Jones@} \\  % no extra space here
\honorific@{ Mr/Ms@} \fullname@{Jones@}     % extra space before title
\end@{tabular@}
@end example

@noindent
To fix this, change to
@code{\newcommand@{\fullname@}[1]@{\ignorespaces\@@honorific~#1@}}.

The @code{\ignorespaces} is also often used in a @code{\newenvironment}
at the end of the @var{begin} clause, that is, as part of the second
argument, as in @code{\begin@{newenvironment@}@{@var{env
name}@}@{... \ignorespaces@}@{...@}}.

To strip spaces off the end of an environment use
@code{\ignorespacesafterend}.  An example is that this will show a much
larger vertical space between the first and second environments than
between the second and third.

@example
\newenvironment@{eq@}@{\begin@{equation@}@}@{\end@{equation@}@}
\begin@{eq@}
e=mc^2
\end@{eq@}
\begin@{equation@}
F=ma
\end@{equation@}
\begin@{equation@}
E=IR
\end@{equation@}
@end example

Putting a comment character@tie{}@code{%} immediately after the
@code{\end@{eq@}} will make the vertical space disappear, but that is
inconvenient.  The solution is to change to
@code{\newenvironment@{eq@}@{\begin@{equation@}@}@{\end@{equation@}\ignorespacesafterend@}}.


@node Counters
@chapter Counters

@cindex counters, a list of
@cindex variables, a list of

Everything @LaTeX{} numbers for you has a counter associated with
it. The name of the counter is often the same as the name of the
environment or command associated with the number, except that the
counter's name has no backslash@tie{}@code{\}.  Thus, associated with
the @code{\chapter} command is the @code{chapter} counter that keeps
track of the chapter number.  

Below is a list of the counters used in @LaTeX{}'s standard document
classes to control numbering.

@example
part            paragraph       figure          enumi
chapter         subparagraph    table           enumii
section         page            footnote        enumiii
subsection      equation        mpfootnote      enumiv
subsubsection
@end example

The @code{mpfootnote} counter is used by the @code{\footnote} command
inside of a minipage (@pxref{minipage}).  The counters @code{enumi}
through @code{enumiv} are used in the @code{enumerate} environment, for
up to four levels of nesting (@pxref{enumerate}).

Counters can have any integer value but they are typically positive.

New counters are created with @code{\newcounter}.  @xref{\newcounter}.


@menu
* \alph \Alph \arabic \roman \Roman \fnsymbol:: Print value of a counter.
* \usecounter::           Use a specified counter in a list environment.
* \value::                Use the value of a counter in an expression.  
* \setcounter::           Set the value of a counter.
* \addtocounter::         Add a quantity to a counter.
* \refstepcounter::       Add to a counter.
* \stepcounter::          Add to a counter, resetting subsidiary counters.
* \day & \month & \year:: Numeric date values.
@end menu


@node \alph \Alph \arabic \roman \Roman \fnsymbol
@section @code{\alph \Alph \arabic \roman \Roman \fnsymbol}: Printing counters

@cindex counters, printing

Print the value of a counter, in a specified style.  For instance, if
the counter @var{counter} has the value 1 then a
@code{\alph@{@var{counter}@}} in your source will result in a lowercase
letter@tie{}a appearing in the output.

All of these commands take a single counter as an argument, for
instance, @code{\alph@{enumi@}}.  Note that the counter name does not
start with a backslash.

@ftable @code
@item \alph@{@var{counter}@}
Print the value of @var{counter} in lowercase letters: `a', `b',
@enddots{} If the counter's value is less than 1 or more than 26 then
you get @samp{LaTeX Error: Counter too large.}

@item \Alph@{@var{counter}@}
Print in uppercase letters: `A', `B', @enddots{} If the counter's value
is less than 1 or more than 26 then you get @samp{LaTeX Error: Counter
too large.}

@item \arabic@{@var{counter}@}
Print in Arabic numbers such as @samp{5} or @samp{-2}.

@item \roman@{@var{counter}@}
Print in lowercase roman numerals: `i', `ii', @enddots{} If the
counter's value is less than 1 then you get no warning or error but
@LaTeX{} does not print anything in the output.

@item \Roman@{@var{counter}@}
Print in uppercase roman numerals: `I', `II', @enddots{} If the
counter's value is less than 1 then you get no warning or error but
@LaTeX{} does not print anything in the output.

@item \fnsymbol@{@var{counter}@}
Prints the value of @var{counter} using a sequence of nine symbols that
are traditionally used for labeling footnotes.  The value of
@var{counter} should be between@tie{}1 and@tie{}9, inclusive.  If the
counter's value is less than 0 or more than 9 then you get @samp{LaTeX
Error: Counter too large}, while if it is 0 then you get no error or
warning but @LaTeX{} does not output anything.

Here are the symbols:

@multitable  @columnfractions .10 .30 .30 .30
@headitem Number@tab Name@tab Command@tab Symbol
@item
1@tab asterisk@tab@code{\ast}@tab@iftexthenelse{@math{\ast},*}
@item
2@tab dagger@tab@code{\dagger}@tab@BES{2020,\dagger}
@item
3@tab ddagger@tab@code{\ddagger}@tab@BES{2021,\ddagger}
@item
4@tab section-sign@tab@code{\S}@tab@BES{00A7,\S}
@item
5@tab paragraph-sign@tab@code{\P}@tab@BES{00B6,\P}
@item
6@tab double-vert@tab@code{\parallel}@tab@BES{2016,\parallel}
@item
7@tab double-asterisk@tab@code{\ast\ast}@tab@iftexthenelse{@math{\ast\ast},**}
@item
8@tab
  double-dagger@tab@code{\dagger\dagger}@tab@BES{2020,\dagger}@BES{2020,\dagger}
@item
9@tab
  double-ddagger@tab@code{\ddagger\ddagger}@tab@BES{2021,\ddagger}@BES{2021,\ddagger}
@end multitable

@end ftable


@node \usecounter
@section @code{\usecounter}

@findex \usecounter
@cindex list items, specifying counter
@cindex numbered items, specifying counter

Synopsis:

@example
\usecounter@{@var{counter}@}
@end example

Used in the second argument of the @code{list} environment
(@pxref{list}), this declares that list items will be numbered by
@var{counter}.  It initializes @var{counter} to zero, and arranges that
when @code{\item} is called without its optional argument then
@var{counter} is incremented by @code{\refstepcounter}, making its value
be the current @code{ref} value (@pxref{\ref}).  This command is fragile
(@pxref{\protect}).

Put in the document preamble, this example makes a new list environment
enumerated with @var{testcounter}:

@example
\newcounter@{testcounter@}
\newenvironment@{test@}@{%
  \begin@{list@}@{@}@{%
    \usecounter@{testcounter@}
  @}
@}@{%
  \end@{list@}
@}
@end example


@node \value
@section @code{\value}

@findex \value
@cindex counters, getting value of

Synopsis:

@example
\value@{@var{counter}@}
@end example

Expands to the value of the counter @var{counter}. (Note that the name
of a counter does not begin with a backslash.)

This example outputs @samp{Test counter is@tie{}6. Other counter
is@tie{}5.}.

@example
\newcounter@{test@} \setcounter@{test@}@{5@}
\newcounter@{other@} \setcounter@{other@}@{\value@{test@}@}
\addtocounter@{test@}@{1@}

Test counter is \arabic@{test@}.
Other counter is \arabic@{other@}.
@end example

The @code{\value} command is not used for typesetting the value of the
counter.  For that, see @ref{\alph \Alph \arabic \roman \Roman \fnsymbol}.

It is often used in @code{\setcounter} or @code{\addtocounter} but
@code{\value} can be used anywhere that @LaTeX{} expects a number, such
as in @code{\hspace@{\value@{foo@}\parindent@}}.  It must not be
preceded by @code{\protect} (@pxref{\protect}).

This example inserts @code{\hspace@{4\parindent@}}.

@example
\setcounter@{myctr@}@{3@} \addtocounter@{myctr@}@{1@}
\hspace@{\value@{myctr@}\parindent@}
@end example


@node \setcounter
@section @code{\setcounter}

@findex \setcounter
@cindex counters, setting
@cindex setting counters

Synopsis:

@example
\setcounter@{@var{counter}@}@{@var{value}@}
@end example

Globally set the counter @var{counter} to have the value of the
@var{value} argument, which must be an integer.  Thus, you can set a
counter's value as @code{\setcounter@{section@}@{5@}}.  Note that the
counter name does not start with a backslash.

In this example if the counter @code{theorem} has value 12 then the
second line will print @samp{XII}.

@example
\setcounter@{exercise@}@{\value@{theorem@}@}
Here it is in Roman: \Roman@{exercise@}.
@end example


@node \addtocounter
@section @code{\addtocounter}

@findex \addtocounter

Synopsis:

@example
\addtocounter@{@var{counter}@}@{@var{value}@
@end example

Globally increment @var{counter} by the amount specified by the
@var{value} argument, which may be negative.

In this example the section value appears as @samp{VII}.

@example
\setcounter@{section@}@{5@}
\addtocounter@{section@}@{2@}
Here it is in Roman: \Roman@{section@}.
@end example


@node \refstepcounter
@section @code{\refstepcounter}

@findex \refstepcounter

Synopsis:

@example
\refstepcounter@{@var{counter}@}
@end example

Globally increments the value of @var{counter} by one, as does
@code{\stepcounter} (@pxref{\stepcounter}).  The difference is that this
command resets the value of any counter numbered within it.  (For the
definition of ``counters numbered within'', @pxref{\newcounter}.)

In addition, this command also defines the current @code{\ref} value
to be the result of @code{\thecounter}.

While the counter value is set globally, the @code{\ref} value is set
locally, i.e., inside the current group.


@node \stepcounter
@section @code{\stepcounter}

@findex \stepcounter

Synopsis:

@example
\stepcounter@{@var{counter}@}
@end example

Globally adds one to @var{counter} and resets all counters numbered
within it.  (For the definition of ``counters numbered within'',
@pxref{\newcounter}.)

This command differs from @code{\refstepcounter} in that this one does
not influence references@tie{}--- it does not define the current
@code{\ref} value to be the result of @code{\thecounter}
(@pxref{\refstepcounter}).


@node \day & \month & \year
@section @code{\day} & @code{\month} & @code{\year}

@findex \day
@findex \month
@findex \year

@LaTeX{} defines the counter @code{\day} for the day of the month
(nominally with value between 1 and 31), @code{\month} for the month of
the year (nominally with value between 1 and 12), and year @code{\year}.
When @TeX{} starts up, they are set from the current values on the
system.  The related command @code{\today} produces a string
representing the current day (@pxref{\today}).

They counters are not updated as the job progresses so in principle they
could be incorrect by the end.  In addition, @TeX{} does no sanity
check:

@example
\day=-2 \month=13 \year=-4 \today
@end example

@noindent
gives no error or warning and results in the output @samp{-2, -4} (the
bogus month value produces no output).


@node Lengths
@chapter Lengths

@cindex lengths, defining and using

A @dfn{length} is a measure of distance.  Many @LaTeX{} commands take a
length as an argument.

Lengths come in two types.  A @dfn{rigid length} such as @code{10pt}
does not contain a @code{plus} or @code{minus} component.  (Plain @TeX{}
calls this a @dfn{dimen}.)  A @dfn{rubber length} (what Plain @TeX{}
calls a @dfn{skip}) such as as with @code{1cm plus0.05cm minus0.01cm}
can contain either or both of those components.  In that rubber length,
the @code{1cm} is the @dfn{natural length} while the other two, the
@code{plus} and @code{minus} components, allow @TeX{} to stretch or
shrink the length to optimize placement.

The illustrations below use these two commands.

@example
% make a black bar 10pt tall and #1 wide
\newcommand@{\blackbar@}[1]@{\rule@{#1@}@{10pt@}@}

% Make a box around #2 that is #1 wide (excluding the border)
\newcommand@{\showhbox@}[2]@{%
  \fboxsep=0pt\fbox@{\hbox to #1@{#2@}@}@} 
@end example

@noindent
This example uses those commands to show a black bar 100@tie{}points
long between @samp{XXX} and @samp{YYY}.  This length is rigid.

@example
XXX\showhbox@{100pt@}@{\blackbar@{100pt@}@}YYY
@end example

As for rubber lengths, shrinking is simpler one: with @code{1cm minus
0.05cm}, the natural length is 1@dmn{cm} but @TeX{} can shrink it down
as far as 0.95@dmn{cm}.  Beyond that, @TeX{} refuses to shrink any more.
Thus, below the first one works fine, producing a space of
98@tie{}points between the two bars.

@example
XXX\showhbox@{300pt@}@{%
  \blackbar@{101pt@}\hspace@{100pt minus 2pt@}\blackbar@{101pt@}@}YYY

XXX\showhbox@{300pt@}@{%
  \blackbar@{105pt@}\hspace@{100pt minus 1pt@}\blackbar@{105pt@}@}YYY
@end example

@noindent
But the second one gets a warning like @samp{Overfull \hbox (1.0pt too
wide) detected at line 17}.  In the output the first @samp{Y} is
overwritten by the end of the black bar, because the box's material is
wider than the 300@dmn{pt} allocated, as @TeX{} has refused to shrink
the total to less than 309@tie{}points.

Stretching is like shrinking except that if @TeX{} is asked to stretch
beyond the given amount, it will do it.  Here the first line is fine,
producing a space of 110@tie{}points between the bars.

@example
XXX\showhbox@{300pt@}@{%
  \blackbar@{95pt@}\hspace@{100pt plus 10pt@}\blackbar@{95pt@}@}YYY

XXX\showhbox@{300pt@}@{%
  \blackbar@{95pt@}\hspace@{100pt plus 1pt@}\blackbar@{95pt@}@}YYY
@end example

@noindent
In the second line @TeX{} needs a stretch of 10@tie{}points and only
1@tie{}point was specified.  @TeX{} stretches the space to the required
length but it gives you a warning like @samp{Underfull \hbox (badness
10000) detected at line 22}.  (We won't discuss badness.)

You can put both stretch and shrink in the same length, as in
@code{1ex plus 0.05ex minus 0.02ex}.

If @TeX{} is setting two or more rubber lengths then it allocates the
stretch or shrink in proportion.

@example
XXX\showhbox@{300pt@}@{%
  \blackbar@{100pt@}%  left
  \hspace@{0pt plus 50pt@}\blackbar@{80pt@}\hspace@{0pt plus 10pt@}%  middle
  \blackbar@{100pt@}@}YYY  % right
@end example

@noindent
The left and right bars take up 100@tie{}points, so the middle needs
another 100.  The middle bar is 80@tie{}points so the two
@code{\hspace}'s must stretch 20@tie{}points.  Because the two are
@code{plus 50pt} and @code{plus 10pt}, @TeX{} gets 5/6 of the stretch
from the first space and 1/6 from the second.

The @code{plus} or @code{minus} component of a rubber length can contain
a @dfn{fill} component, as in @code{1in plus2fill}.  This gives the
length infinite stretchability or shrinkability so that @TeX{} could set
it to any distance.  Here the two figures will be equal-spaced across
the page.

@example
\begin@{minipage@}@{\linewidth@}
  \hspace@{0pt plus 1fill@}\includegraphics@{godel.png@}%
  \hspace@{0pt plus 1fill@}\includegraphics@{einstein.png@}%
  \hspace@{0pt plus 1fill@}
\end@{minipage@}
@end example

@TeX{} actually has three levels of infinity for glue components:
@code{fil}, @code{fill}, and @code{filll}.  The later ones are more
infinite than the earlier ones.  Ordinarily document authors only use
the middle one (@pxref{\hfill} and @pxref{\vfill}).

Multiplying a rubber length by a number turns it into a rigid length, so
that after @code{\setlength@{\ylength@}@{1in plus 0.2in@}} and
@code{\setlength@{\zlength@}@{3\ylength@}} then the value of
@code{\zlength} is @code{3in}.

@menu
* Units of length::     The units that @LaTeX{} knows.
* \setlength::          Set the value of a length.
* \addtolength::        Add a quantity to a length.
* \settodepth::         Set a length to the depth of something.
* \settoheight::        Set a length to the height of something.
* \settowidth::         Set a length to the width of something.
@c * Predefined lengths::  Lengths that are, like, predefined.
@end menu


@node Units of length
@section Units of length

@cindex units, of length

@TeX{} and @LaTeX{} know about these units both inside and outside of
math mode.

@table @code
@item pt 
@findex pt
@cindex Point
@anchor{units of length pt}
Point, 1/72.27 inch.  The conversion to metric units, to two decimal
places, is 1@dmn{point} = 2.85@dmn{mm} = 28.45@dmn{cm}. 

@item pc
@cindex pica
@findex pc
@anchor{units of length pc}
Pica, 12 pt

@item in 
@findex in
@findex inch
@anchor{units of length in}
Inch,  72.27 pt

@item  bp 
@findex bp
@cindex Big point
@anchor{units of length bp}
Big point, 1/72 inch.  This length is the definition of a point in
PostScript and many desktop publishing systems.

@item cm 
@cindex Centimeter
@findex cm
@anchor{units of length cm}
Centimeter

@item mm 
@cindex Millimeter
@findex mm
@anchor{units of length mm}
Millimeter

@item dd 
@cindex Didot point
@findex dd
@anchor{units of length dd}
Didot point, 1.07 pt

@item cc 
@cindex Cicero
@findex cc
@anchor{units of length cc}
Cicero, 12 dd

@item sp 
@cindex Scaled point
@findex sp
@anchor{units of length sp}
Scaled point, 1/65536 pt

@end table 

@cindex ex
@cindex x-height
@findex ex
@cindex m-width
@cindex em
@findex em
@anchor{Lengths/em}
@anchor{Lengths/en}
@anchor{Lengths/ex}
@anchor{units of length em}
@anchor{units of length en}
@anchor{units of length ex}
Two other lengths that are often used are values set by the designer of
the font.  The x-height of the current font @dfn{ex}, traditionally the
height of the lowercase letter x, is often used for vertical
lengths. Similarly @dfn{em}, traditionally the width of the capital
letter M, is often used for horizontal lengths (there is also
@code{\enspace}, which is @code{0.5em}).  Use of these can help make a
definition work better across font changes.  For example, a definition
of the vertical space between list items given as
@code{\setlength@{\itemsep@}@{1ex plus 0.05ex minus 0.01ex@}} is more
likely to still be reasonable if the font is changed than a definition
given in points.

@cindex mu, math unit
@findex mu
In math mode, many definitions are expressed in terms of the math unit
@dfn{mu} given by 1 em = 18 mu, where the em is taken from the current
math symbols family.  @xref{Spacing in math mode}.


@node \setlength
@section @code{\setlength}

@findex \setlength
@cindex lengths, setting

Synopsis:

@example
\setlength@{@var{len}@}@{@var{amount}@}
@end example

Set the length @var{len} to @var{amount}.  The length name @var{len}
must begin with a backslash, @code{\}.  The @code{amount} can be a
rubber length (@pxref{Lengths}).  It can be positive, negative or zero,
and can be in any units that @LaTeX{} understands (@pxref{Units of
length}).

Below, with @LaTeX{}'s defaults the first paragraph will be indented
while the second will not.

@example
I told the doctor I broke my leg in two places.

\setlength@{\parindent@}@{0em@}
He said stop going to those places.
@end example

If you did not declare @var{len} with @code{\newlength}, for example if
you mistype the above as
@code{\newlength@{\specparindent@}\setlength@{\sepcparindent@}@{...@}},
then you get an error like @samp{Undefined control sequence. <argument>
\sepcindent}.  If you omit the backslash at the start of the length name
then you get an error like @samp{Missing number, treated as zero. <to be
read again> \relax l.19 \setlength@{specparindent@}@{0.6\parindent@}}


@node \addtolength
@section @code{\addtolength}

@findex \addtolength
@cindex lengths, adding to

Synopsis:

@example
\addtolength@{@var{len}@}@{@var{amount}@}
@end example

Increment the length @var{len} by @var{amount}.  The length name
@var{len} begins with a backslash, @code{\}.  The @code{amount} is a
rubber length (@pxref{Lengths}).  It can be positive, negative or zero,
and can be in any units that @LaTeX{} understands (@pxref{Units of
length}).

Below, if @code{\parskip} starts with the value @code{0pt plus 1pt} 

@example
Doctor: how is the boy who swallowed the silver dollar?
\addtolength@{\parskip@}@{1pt@}

Nurse: no change.
@end example

@noindent
then it has the value @code{1pt plus 1pt} for the second paragraph.

If you did not declare the length @var{len} with @code{\newlength}, if
for example you mistype the above as
@code{\addtolength@{\specparindent@}@{0.6\praindent@}}, then you get
something like @samp{Undefined control sequence. <argument> \praindent}.
If you leave off the backslash at the start of @var{len}, as in
@code{\addtolength@{parindent@}@{1pt@}}, then you get something like
@samp{You can't use `the letter p' after \advance}.


@node \settodepth
@section @code{\settodepth}

@findex \settodepth

Synopsis:

@example
\settodepth@{@var{len}@}@{@var{text}@}
@end example

Set the length @var{len} to the depth of box that @LaTeX{} gets on
typesetting the @var{text} argument.  The length name @var{len} must
begin with a backslash, @code{\}.

This will show how low the character descenders go.

@example
\newlength@{\alphabetdepth@}
\settodepth@{\alphabetdepth@}@{abcdefghijklmnopqrstuvwxyz@}
\the\alphabetdepth
@end example

If you did not set aside the length @var{len}, if for example you
mistype the above as @code{\settodepth@{\aplhabetdepth@}@{abc...@}},
then you get something like @samp{Undefined control sequence. <argument>
\aplhabetdepth}.  If you leave the backslash out of @var{len}, as in
@code{\settodepth@{alphabetdepth@}@{...@}} then you get something like
@samp{Missing number, treated as zero. <to be read again> \setbox}.


@node \settoheight
@section @code{\settoheight}

@findex \settoheight

Synopsis:

@example
\settoheight@{@var{len}@}@{text@}
@end example

Sets the length @var{len} to the height of box that @LaTeX{} gets on
typesetting the @code{text} argument.  The length name @var{len} must
begin with a backslash, @code{\}.

This will show how high the characters go.

@example
\newlength@{\alphabetheight@}
\settoheight@{\alphabetheight@}@{abcdefghijklmnopqrstuvwxyz@}
\the\alphabetheight
@end example

If no such length @var{len} has been declared with @code{\newlength}, if
for example you mistype as
@code{\settoheight@{\aplhabetheight@}@{abc...@}}, then you get something
like @samp{Undefined control sequence. <argument> \alphabetheight}.  If
you leave the backslash out of @var{len}, as in
@code{\settoheight@{alphabetheight@}@{...@}} then you get something like
@samp{Missing number, treated as zero. <to be read again> \setbox}.


@node \settowidth
@section @code{\settowidth}

@findex \settowidth

Synopsis:

@example
\settowidth@{@var{len}@}@{@var{text}@}
@end example

Set the length @var{len} to the width of the box that @LaTeX{} gets on
typesetting the @var{text} argument.  The length name @var{len} must
begin with a backslash, @code{\}.

This measures the width of the lowercase ASCII alphabet.

@example
\newlength@{\alphabetwidth@}
\settowidth@{\alphabetwidth@}@{abcdefghijklmnopqrstuvwxyz@}
\the\alphabetwidth
@end example

If no such length @var{len} has been set aside, if for example you
mistype the above as @code{\settowidth@{\aplhabetwidth@}@{abc...@}},
then you get something like @samp{Undefined control sequence. <argument>
\aplhabetwidth}.  If you leave the backslash out of @var{len}, as in
@code{\settoheight@{alphabetwidth@}@{...@}} then you get something like
@samp{Missing number, treated as zero. <to be read again> \setbox}.


@node Making paragraphs
@chapter Making paragraphs

@cindex making paragraphs
@cindex paragraphs

To start a paragraph, just type some text.  To end the current
paragraph, put an empty line.  This is three paragraphs, separated by
two empty lines.

@example
It is a truth universally acknowledged, that a single man in possession
of a good fortune, must be in want of a wife.

However little known the feelings or views of such a man may be on his
first entering a neighbourhood, this truth is so well fixed in the minds
of the surrounding families, that he is considered the rightful property
of some one or other of their daughters.

``My dear Mr. Bennet,'' said his lady to him one day,
``have you heard that Netherfield Park is let at last?''
@end example

The separator lines must be empty, including not containing a comment
character, @code{%}.

Once @LaTeX{} has gathered all of a paragraph's contents it divides that
content into lines in a way that is optimized over the entire paragraph
(@pxref{Line breaking}).

There are places where a new paragraph is not permitted.  Don't put a
blank line in math mode (@pxref{Modes}); here the line before the
@code{\end@{equation@}}

@example
\begin@{equation@}
  2^@{|S|@} > |S|

\end@{equation@}
@end example

@noindent
will get you the error @samp{Missing $ inserted}.  Similarly, the blank
line in this @code{section} argument

@example
\section@{aaa

bbb@}
@end example

@noindent
gets @samp{Runaway argument? @{aaa ! Paragraph ended before \@@sect was
complete}.


@menu
* \par::                     End the current paragraph.
* \indent & \noindent::      Go into horizontal mode, possibly with an indent.
* \parindent & \parskip::    Space added before paragraphs.
* Marginal notes::           Put remarks in the margin.
@end menu


@node \par
@section @code{\par}

@findex \par
@cindex paragraph, ending

Synopsis (note that while reading the input @TeX{} converts two
consecutive newlines to a @code{\par}):

@example
\par
@end example

End the current paragraph.  The usual way to separate paragraphs is with
a blank line but the @code{\par} command is entirely equivalent.  This
command is robust (@pxref{\protect}).

This example uses @code{\par} rather than a blank line simply for
readability.

@example
\newcommand@{\syllabusLegalese@}@{%
  \whatCheatingIs\par\whatHappensWhenICatchYou@}
@end example

In LR mode or a vertical mode the @code{\par} command does nothing but
it terminates paragraph mode, switching @LaTeX{} to vertical mode
(@pxref{Modes}).

You cannot use the @code{\par} command in a math mode.  You also cannot
use it in the argument of many commands, such as the @code{\section}
command (@pxref{Making paragraphs} and @ref{\newcommand &
\renewcommand}).

The @code{\par} command is not the same as the @code{\paragraph}
command. The latter is, like @code{\section} or @code{\subsection}, a
sectioning unit used by the standard @LaTeX{} documents
(@pxref{\subsubsection & \paragraph & \subparagraph}).

The @code{\par} command is not the same as @code{\newline} or the line
break double backslash, @code{\\}.  The difference is that @code{\par}
ends the paragraph, not just the line, and also triggers the addition of
the between-paragraph vertical space @code{\parskip} (@pxref{\parindent
& \parskip}).

The output from this example

@example
xyz

\setlength@{\parindent@}@{3in@}
\setlength@{\parskip@}@{5in@}
\noindent test\indent test1\par test2 
@end example

@noindent
is: after @samp{xyz} there is a vertical skip of 5@tie{}inches and then
@samp{test} appears, aligned with the left margin.  On the same line,
there is an empty horizontal space of 3@tie{}inches and then
@samp{test1} appears.  Finally. there is a vertical space of
5@tie{}inches, followed by a fresh paragraph with a paragraph indent of
3@tie{}inches, and then @LaTeX{} puts the text @samp{test2}.


@node \indent & \noindent
@section @code{\indent} & @code{\noindent}

@findex \indent
@findex \noindent
@findex \parindent
@cindex indent, forcing

Synopsis:

@example
\indent
@end example

@noindent or

@example
\noindent
@end example

Go into horizontal mode (@pxref{Modes}).  The @code{\indent} command
first outputs an empty box whose width is @code{\parindent}.  These
commands are robust (@pxref{\protect}).

Ordinarily you create a new paragraph by putting in a blank line.
@xref{\par} for the difference between this command and @code{\par}.  To
start a paragraph without an indent, or to continue an interrupted
paragraph, use @code{\noindent}.

In the middle of a paragraph the @code{\noindent} command has no effect,
because @LaTeX{} is already in horizontal mode there.  The
@code{\indent} command's only effect is to output a space.

This example starts a fresh paragraph.

@example
... end of the prior paragraph.

\noindent This paragraph is not indented.
@end example

@noindent
and this continues an interrupted paragraph.

@example
The data 

\begin@{center@}
  \begin@{tabular@}@{rl@} ... \end@{tabular@}
\end@{center@}

\noindent shows this clearly.
@end example

To omit indentation in the entire document put
@code{\setlength@{\parindent@}@{0pt@}} in the preamble.  If you do that,
you may want to also set the length of spaces between paragraphs,
@code{\parskip} (@pxref{\parindent & \parskip}).

@PkgIndex{indentfirst}
Default @LaTeX{} styles have the first paragraph after a section that is
not indented, as is traditional typesetting in English.  To change that,
look on CTAN for the package @code{indentfirst}.


@node \parindent & \parskip
@section @code{\parindent} & @code{\parskip}

@findex \parindent
@findex \parskip
@cindex paragraph indentation
@cindex vertical space before paragraphs

Synopsis:

@example
\setlength@{\parskip@}@{@var{horizontal len}@}
\setlength@{\parinden@}@{@var{vertical len}@}
@end example

Both are a rubber lengths (@pxref{Lengths}).  They give the indentation
of ordinary paragraphs, not paragraphs inside minipages
(@pxref{minipage}), and the vertical space between paragraphs.

This, put in the preamble,

@example
\setlength@{\parindent@}@{0em@}
\setlength@{\parskip@}@{1ex@}
@end example

@noindent
arranges that the document will have paragraphs that are not indented,
but instead are vertically separated by about the height of a lowercase
@samp{x}.

In standard @LaTeX{} documents, the default value for @code{\parindent}
in one-column documents is @code{15pt} when the default text size is
@code{10pt} , @code{17pt} for @code{11pt}, and @code{1.5em} for
@code{12pt}.  In two-column documents it is @code{1em}.  The default
value for @code{\parskip} in @LaTeX{}'s standard document styles is
@code{0pt plus1pt}.


@node Marginal notes
@section Marginal notes

@cindex marginal notes
@cindex notes in the margin
@cindex remarks in the margin
@findex \marginpar

Synopsis, one of:

@example
\marginpar@{@var{right}@}
\marginpar[@var{left}]@{@var{right}@}
@end example

Create a note in the margin.  The first line of the note will have the
same baseline as the line in the text where the @code{\marginpar}
occurs.

The margin that @LaTeX{} uses for the note depends on the current layout
(@pxref{Document class options}) and also on @code{\reversemarginpar}
(see below).  If you are using one-sided layout (document option
@code{oneside}) then it goes in the right margin.  If you are using
two-sided layout (document option @code{twoside}) then it goes in the
outside margin.  If you are in two-column layout (document option
@code{twocolumn}) then it goes in the nearest margin.

@findex \reversemarginpar
@findex \normalmarginpar
If you declare @code{\reversemarginpar} then @LaTeX{} will place
subsequent marginal notes in the opposite margin to that given in the
prior paragraph.  Revert that to the default position with
@code{\normalmarginpar}.

When you specify the optional argument @var{left} then it is used for
a note in the left margin, while the mandatory argument @var{right} is
used for a note in the right margin.

Normally, a note's first word will not be hyphenated.  You can enable
hyphenation there by beginning @var{left} or @var{right} with
@code{\hspace@{0pt@}}.

These parameters affect the formatting of the note:

@ftable @code
@item \marginparpush
@anchor{marginal notes marginparpush}
Minimum vertical space between notes; default @samp{7pt} for
@samp{12pt} documents, @samp{5pt} else.

@item \marginparsep
@anchor{marginal notes marginparsep}
Horizontal space between the main text and the note; default
@samp{11pt} for @samp{10pt} documents, @samp{10pt} else.

@item \marginparwidth
@anchor{marginal notes marginparwidth}
Width of the note itself; default for a one-sided @samp{10pt} document
is @samp{90pt}, @samp{83pt} for @samp{11pt}, and @samp{68pt} for
@samp{12pt}; @samp{17pt} more in each case for a two-sided document.
In two column mode, the default is @samp{48pt}.

@end ftable

The standard @LaTeX{} routine for marginal notes does not prevent
notes from falling off the bottom of the page.
@c  @TeX{} FAQ entry on this topic (xx when there):
@c @url{http://www.tex.ac.uk/cgi-bin/texfaq2html?label=marginparside}.
@c (+marginfix)


@node Math formulas
@chapter Math formulas

@cindex math formulas
@cindex formulas, math
@cindex math mode, entering
@EnvIndex{math}
@EnvIndex{displaymath}
@EnvIndex{equation}

Produce mathematical text by putting @LaTeX{} into math mode or display
math mode (@pxref{Modes}).  This example shows both.

@example
The wave equation for \( u \) is
\begin@{displaymath@}
  \frac@{\partial^2u@}@{\partial t^2@} = c^2\nabla^2u
\end@{displaymath@}
where \( \nabla^2 \) is the spatial Laplacian and \( c \) is constant.
@end example

@noindent
Math mode is for inline mathematics.  In the above example it is invoked
by the starting @code{\(} and finished by the matching ending @code{\)}.
Display math mode is for displayed equations and here is invoked by the
@code{displaymath} environment.  Note that any mathematical text
whatever, including mathematical text consisting of just one character,
is handled in math mode.

When in math mode or display math mode, @LaTeX{} handles many aspects of
your input text differently than in other text modes.  For example,

@example
contrast x+y with \( x+y \)
@end example

@noindent
in math mode the letters are in italics and the spacing around the plus
sign is different.

There are three ways to make inline formulas, to put @LaTeX{} in math
mode.

@example
\( @var{mathematical material} \)
$ @var{mathematical material} $
\begin@{math@} @var{mathematical material} \end@{math@}
@end example

@noindent
The first form is preferred and the second is quite common, but the
third form is rarely used.  You can sometimes use one and sometimes
another, as in @code{\(x\) and $y$}.  You can use these in paragraph
mode or in LR mode (@pxref{Modes}).

To make displayed formulas, put @LaTeX{} into display math mode with
either:

@example
\begin@{displaymath@}
  @var{mathematical material}
\end@{displaymath@}
@end example

@noindent
or

@example
\begin@{equation@}
  @var{mathematical material}
\end@{equation@}
@end example

@noindent
(@pxref{displaymath}, @pxref{equation}).  The only difference is that
with the @code{equation} environment, @LaTeX{} puts a formula number
alongside the formula.  The construct @code{\[ @var{math} \]} is
equivalent to @code{\begin@{displaymath@} @var{math}
\end@{displaymath@}}.  These environments can only be used in paragraph
mode (@pxref{Modes}).

@findex \displaystyle
The two mathematics modes are similar, but there are some differences.
One involves the placement of subscripts and superscripts; in display
math mode they are further apart and in inline math mode they are closer
together.

Sometimes you want the display math typographical treatment to happen in
the inline math mode.  For this, the @code{\displaystyle} declaration
forces the size and style of the formula to be that of
@code{displaymath}.  Thus @code{\(\displaystyle \sum_@{n=0@}^\infty
x_n\)} will have the limits above and below the summation sign, not next
to it.  Another example is that

@example
\begin@{tabular@}@{r|cc@}
  \textsc@{Name@}  &\textsc@{Series@}  &\textsc@{Sum@}  \\  \hline
  Arithmetic     &\( a+(a+b)+(a+2b)+\cdots+(a+(n-1)b) \)
                   &\( na+(n-1)n\cdot\frac@{b@}@{2@}\)  \\
  Geometric      &\( a+ab+ab^2+\cdots+ab^@{n-1@} \)
                   &\(\displaystyle a\cdot\frac@{1-b^n@}@{1-b@}\)  \\
\end@{tabular@}
@end example

@noindent
because it has no @code{\displaystyle}, the @samp{Arithmetic} line's
fraction will be scrunched.  But, because of its @code{\displaystyle},
the @samp{Geometric} line's fraction will be easy to read, with
characters the same size as in the rest of the line.

@PkgIndex{amsmath}
@PkgIndex{amsfonts}
@PkgIndex{mathtools}
The American Mathematical Society has made freely available a set of
packages that greatly expand your options for writing mathematics,
@file{amsmath} and @file{amssymb} (also be aware of the @file{mathtools}
package that is an extension to, and loads, @file{amsmath}).  New
documents that will have mathematical text should use these packages.
Descriptions of these packages is outside the scope of this document;
see their documentation on CTAN.

@menu
* Subscripts & superscripts::   Also known as exponent or index.
* Math symbols::                Various mathematical squiggles.
* Math functions::              Math function names like sin and exp.
* Math accents::                Accents in math.
* Over- and Underlining::       Things over or under formulas.
* Spacing in math mode::        Thick, medium, thin, and negative spaces.
* Math miscellany::             Stuff that doesn't fit anywhere else.
@end menu


@node Subscripts & superscripts
@section Subscripts & superscripts

@cindex superscript
@cindex subscript
@cindex exponent
@findex _
@findex ^

Synopsis (in math mode or display math mode), one of:

@example
@var{base}^@var{exp}
@var{base}^@{@var{exp}@}
@end example

@noindent
or, one of:

@example
@var{base}_@var{exp}
@var{base}_@{@var{exp}@}
@end example 

Make @var{exp} appear as a superscript of @var{base} (with the caret
character,@tie{}@code{^}) or a subscript (with
underscore,@tie{}@code{_}).

In this example the @code{0}'s and @code{1}'s are subscripts while the
@code{2}'s are superscripts.

@example
\( (x_0+x_1)^2 \leq (x_0)^2+(x_1)^2 \)
@end example 

To have the subscript or superscript contain more than one character,
surround the expression with curly braces, as in @code{e^@{-2x@}}.
This example's fourth line shows curly braces used to group an expression
for the exponent.

@example
\begin@{displaymath@}
  (3^3)^3=27^3=19\,683
  \qquad
  3^@{(3^3)@}=3^@{27@}=7\,625\,597\,484\,987
\end@{displaymath@}
@end example

@LaTeX{} knows how to handle a superscript on a superscript, or a
subscript on a subscript, or supers on subs, or subs on supers.  So,
expressions such as @code{e^@{x^2@}} and @code{x_@{i_0@}} give correct
output.  Note the use in those expressions of curly braces to give the
@var{base} a determined @var{exp}.  If you enter @code{\(3^3^3\)} then
you get @samp{Double superscript}.

@LaTeX{} does the right thing when something has both a subscript and a
superscript.  In this example the integral has both.  They come out in
the correct place without any author intervention.

@example
\begin@{displaymath@}
  \int_@{x=a@}^b f'(x)\,dx = f(b)-f(a)
\end@{displaymath@}
@end example

@noindent
Note the parentheses around @code{x=a} to make the entire expression a
subscript.

To put a superscript or subscript before a symbol, use a construct like
@code{@{@}_t K^2}.  The empty curly braces @code{@{@}} give the
subscript something to attach to and keeps it from accidentally
attaching to a prior symbols.

Using the subscript or superscript command outside of math mode or
display math mode, as in @code{the expression x^2}, will get you
the error @samp{Missing $ inserted}.

@PkgIndex{mhchem}
A common reason to want subscripts outside of a mathematics mode is to
typeset chemical formulas.  There are packages for that such as
@file{mhchem}; see CTAN.


@node Math symbols
@section Math symbols

@cindex math symbols
@cindex symbols, math
@cindex greek letters

@PkgIndex{symbols}

@LaTeX{} provides almost any mathematical or technical symbol that
anyone uses.  For example, if you include @code{$\pi$} in your source,
you will get the pi symbol @BES{03C0,\pi}.  See the @file{Comprehensive
@LaTeX{} Symbol List} at
@url{https://ctan.org/tex-archive/info/symbols/comprehensive/}.

Here is a list of commonly-used symbols.  It is by no means exhaustive.
Each symbol is described with a short phrase, and its symbol class,
which determines the spacing around it, is given in parenthesis.  Unless
said otherwise, the commands for these symbols can be used only in math
mode.  To redefine a command so that it can be used whatever the current
mode, see @ref{\ensuremath}.

@c xx Add Negation: for negations of relevant symbols
@c Useful: http://www.w3.org/TR/WD-math-970515/section6.html

@ftable @code
@item \|
@BES{2225,\|} Parallel (relation). Synonym:@tie{}@code{\parallel}.

@item \aleph
@BES{2135,\aleph} Aleph, transfinite cardinal (ordinary).

@item \alpha
@BES{03B1,\alpha} Lowercase Greek letter alpha (ordinary).

@item \amalg
@BES{2A3F,\amalg} Disjoint union (binary)

@item \angle
@BES{2220,\angle} Geometric angle (ordinary). Similar: less-than
sign@tie{}@code{<} and angle bracket@tie{}@code{\langle}.

@item \approx
@BES{2248,\approx} Almost equal to (relation).

@item \ast
@BES{2217,\ast} Asterisk operator, convolution, six-pointed
(binary). Synonym:@tie{}@code{*}, which is often a superscript or
subscript, as in the Kleene star. Similar:@tie{}@code{\star}, which is
five-pointed, and is sometimes used as a general binary operation, and
sometimes reserved for cross-correlation.

@item \asymp
@BES{224D,\asymp} Asymptotically equivalent (relation).

@item \backslash
\ Backslash (ordinary).  Similar: set minus@tie{}@code{\setminus}, and
@code{\textbackslash} for backslash outside of math mode.

@item \beta
@BES{03B2,\beta} Lowercase Greek letter beta (ordinary).

@item \bigcap
@BES{22C2,\bigcap} Variable-sized, or n-ary, intersection (operator). Similar:
binary intersection@tie{}@code{\cap}.

@item \bigcirc
@BES{26AA,\bigcirc} Circle, larger (binary).  Similar: function
composition@tie{}@code{\circ}.
@c bb Best unicode symbol for this?

@item \bigcup
@BES{22C3,\bigcup} Variable-sized, or n-ary, union (operator). Similar: binary
union@tie{}@code{\cup}.

@item \bigodot
@BES{2A00,\bigodot} Variable-sized, or n-ary, circled dot operator (operator).

@item \bigoplus
@BES{2A01,\bigoplus} Variable-sized, or n-ary, circled plus operator (operator).

@item \bigotimes
@BES{2A02,\bigotimes} Variable-sized, or n-ary, circled times operator (operator).

@item \bigtriangledown
@BES{25BD,\bigtriangledown} Variable-sized, or n-ary, open triangle pointing down
(operator).

@item \bigtriangleup
@BES{25B3,\bigtriangleup} Variable-sized, or n-ary, open triangle pointing up (operator).

@item \bigsqcup
@BES{2A06,\bigsqcup} Variable-sized, or n-ary, square union (operator).

@item \biguplus
@BES{2A04,\biguplus} Variable-sized, or n-ary, union operator with a plus
(operator).  (Note that the name has only one p.)

@item \bigvee
@BES{22C1,\bigvee} Variable-sized, or n-ary, logical-and (operator).

@item \bigwedge
@BES{22C0,\bigwedge} Variable-sized, or n-ary, logical-or (operator).

@item \bot
@BES{22A5,} Up tack, bottom, least element of a partially ordered
set, or a contradiction (ordinary).  See also@tie{}@code{\top}.

@item \bowtie
@BES{22C8,\bowtie} Natural join of two relations (relation).

@item \Box
@BES{25A1,} Modal operator for necessity; square open box
(ordinary).  @value{NeedsAMSSymb}
@c bb Best Unicode equivalent?

@item \bullet
@cindex bullet symbol
@BES{2022,\bullet} Bullet (binary).  Similar: multiplication
dot@tie{}@code{\cdot}.

@item \cap
@BES{2229,\cap} Intersection of two sets (binary).  Similar: variable-sized
operator@tie{}@code{\bigcap}.

@item \cdot
@BES{22C5,\cdot} Multiplication (binary).  Similar: Bullet
dot@tie{}@code{\bullet}.

@item \chi
@BES{03C7,\chi} Lowercase Greek chi (ordinary).

@item \circ
@BES{2218,\circ} Function composition, ring operator (binary).  Similar:
variable-sized operator@tie{}@code{\bigcirc}.

@item \clubsuit
@BES{2663,\clubsuit} Club card suit (ordinary).

@item \complement
@BES{2201,} Set complement, used as a superscript as in
@code{$S^\complement$} (ordinary).  @value{NeedsAMSSymb} Also used:
@code{$S^@{\mathsf@{c@}@}$} or@tie{}@code{$\bar@{S@}$}.

@item \cong
@BES{2245,\cong} Congruent (relation).

@item \coprod
@BES{2210,\coprod} Coproduct (operator).

@item \cup
@BES{222A,\cup} Union of two sets (binary).  Similar: variable-sized
operator@tie{}@code{\bigcup}.

@item \dagger
@BES{2020,\dagger} Dagger relation (binary).

@item \dashv
@BES{22A3,\dashv} Dash with vertical, reversed turnstile (relation).  Similar:
turnstile@tie{}@code{\vdash}.

@item \ddagger
@BES{2021,\ddagger} Double dagger relation (binary).

@item \Delta
@BES{0394,\Delta} Greek uppercase delta, used for increment (ordinary).

@item \delta
@BES{03B4,\delta} Greek lowercase delta (ordinary).

@item \Diamond
@BES{25C7,} Large diamond operator (ordinary).  @value{NeedsAMSSymb}

@item \diamond
@BES{22C4,\diamond} Diamond operator (binary).  Similar: large
diamond@tie{}@code{\Diamond}, circle bullet@tie{}@code{\bullet}.

@item \diamondsuit
@BES{2662,\diamondsuit} Diamond card suit (ordinary).

@item \div
@BES{00F7,\div} Division sign (binary).

@item \doteq
@BES{2250,\doteq} Approaches the limit (relation).  Similar: geometrically equal
to@tie{}@code{\Doteq}.

@item \downarrow
@BES{2193,\downarrow} Down arrow, converges (relation).  Similar:
@code{\Downarrow} double line down arrow.

@item \Downarrow
@BES{21D3,\Downarrow} Double line down arrow (relation).  Similar:
@code{\downarrow} single line down arrow.

@item \ell
@BES{2113,\ell} Lowercase cursive letter l (ordinary).

@item \emptyset
@BES{2205,\emptyset} Empty set symbol (ordinary).  The variant form is
@code{\varnothing}.
@c bb Why Unicode has \revemptyset but no \emptyset?
	
@item \epsilon
@BES{03F5,\epsilon} Lowercase lunate epsilon (ordinary). Similar to
Greek text letter. More widely used in mathematics is the script small
letter epsilon @code{\varepsilon}@tie{}@BES{03B5,\varepsilon}. Related:
the set membership relation @code{\in}@tie{}@BES{2208,\in}.
@c src: David Carlisle http://tex.stackexchange.com/a/98018/339 and
@c Unicode referenced there asserts varepsilon is much more widely used.

@item \equiv
@BES{2261,\equiv} Equivalence (relation).

@item \eta
@BES{03B7,\eta} Lowercase Greek letter (ordinary).

@item \exists
@BES{2203,\exists} Existential quantifier (ordinary).

@item \flat
@BES{266D,\flat} Musical flat (ordinary).

@item \forall
@BES{2200,\forall} Universal quantifier (ordinary).

@item \frown
@BES{2322,\frown} Downward curving arc (ordinary).

@item \Gamma
@BES{0393,\Gamma} uppercase Greek letter (ordinary).

@item \gamma
@BES{03B3,\gamma} Lowercase Greek letter (ordinary).

@item \ge
@BES{2265,\ge} Greater than or equal to (relation).  This is a synonym
for@tie{}@code{\geq}.

@item \geq
@BES{2265,\geq} Greater than or equal to (relation).  This is a synonym
for@tie{}@code{\ge}.

@item \gets
@BES{2190,\gets} Is assigned the value (relation).
Synonym:@tie{}@code{\leftarrow}.

@item \gg
@BES{226B,\gg} Much greater than (relation).  Similar: much less
than@tie{}@code{\ll}.

@item \hbar
@BES{210F,\hbar} Planck constant over two pi (ordinary).

@item \heartsuit
@BES{2661,\heartsuit} Heart card suit (ordinary).

@item \hookleftarrow
@BES{21A9,\hookleftarrow} Hooked left arrow (relation).

@item \hookrightarrow
@BES{21AA,\hookrightarrow} Hooked right arrow (relation).

@item \iff
@BES{27F7,\iff} If and only if (relation).  It is @code{\Longleftrightarrow}
with a @code{\thickmuskip} on either side.

@item \Im
@BES{2111,\Im} Imaginary part (ordinary).  See: real part@tie{}@code{\Re}.

@item \imath
@cindex dotless i, math
Dotless i; used when you are putting an accent on an i (@pxref{Math
accents}).

@item \in
@BES{2208,\in} Set element (relation).  See also: lowercase lunate
epsilon@tie{}@code{\epsilon}@BES{03F5,\epsilon} and small letter script
epsilon@tie{}@code{\varepsilon}.

@item \infty
@BES{221E,\infty} Infinity (ordinary).

@item \int
@BES{222B,\int} Integral (operator).

@item \iota
@BES{03B9,\iota} Lowercase Greek letter (ordinary).

@item \Join
@BES{2A1D,} Condensed bowtie symbol (relation).  Not available in Plain
@TeX{}.

@item \jmath
@cindex dotless j, math
Dotless j; used when you are putting an accent on a j (@pxref{Math
accents}).

@item \kappa
@BES{03BA,\kappa} Lowercase Greek letter (ordinary).

@item \Lambda
@BES{039B,\Lambda} uppercase Greek letter (ordinary).

@item \lambda
@BES{03BB,\lambda} Lowercase Greek letter (ordinary).

@item \land
@BES{2227,\land} Logical and (binary).  This is a synonym for @code{\wedge}.
See also logical or@tie{}@code{\lor}.

@item \langle
@BES{27E8,\langle} Left angle, or sequence, bracket (opening).  Similar:
less-than@tie{}@code{<}. Matches@tie{}@code{\rangle}.

@item \lbrace
@BES{007B,\lbrace} Left curly brace
(opening). Synonym:@tie{}@code{\@{}. Matches@tie{}@code{\rbrace}.

@item \lbrack
@BES{005B,\lbrack} Left square bracket (opening).
Synonym:@tie{}@code{[}. Matches@tie{}@code{\rbrack}.

@item \lceil
@BES{2308,\lceil} Left ceiling bracket, like a square bracket but with the bottom
shaved off (opening). Matches@tie{}@code{\rceil}.

@item \le
@BES{2264,\le} Less than or equal to (relation).  This is a synonym
for@tie{}@code{\leq}.

@item \leadsto
@BES{21DD,} Squiggly right arrow (relation).  @value{NeedsAMSSymb}
To get this symbol outside of math mode you can put
@code{\newcommand*@{\Leadsto@}@{\ensuremath@{\leadsto@}@}} in the
preamble and then use @code{\Leadsto} instead.
@c bb Best Unicode equivalent?

@item \Leftarrow
@BES{21D0,\Leftarrow} Is implied by, double-line left arrow (relation).  Similar:
single-line left arrow@tie{}@code{\leftarrow}.

@item \leftarrow
@BES{2190,\leftarrow} Single-line left arrow (relation).
Synonym:@tie{}@code{\gets}. Similar: double-line left
arrow@tie{}@code{\Leftarrow}.

@item \leftharpoondown
@BES{21BD,\leftharpoondown} Single-line left harpoon, barb under bar (relation).

@item \leftharpoonup
@BES{21BC,\leftharpoonup} Single-line left harpoon, barb over bar (relation).

@item \Leftrightarrow
@BES{21D4,\Leftrightarrow} Bi-implication; double-line double-headed arrow (relation).
Similar: single-line double headed arrow@tie{}@code{\leftrightarrow}.

@item \leftrightarrow
@BES{2194,\leftrightarrow} Single-line double-headed arrow (relation).  Similar:
double-line double headed arrow@tie{}@code{\Leftrightarrow}.

@item \leq
@BES{2264,\leq} Less than or equal to (relation).  This is a synonym
for@tie{}@code{\le}.

@item \lfloor
@BES{230A,\lfloor} Left floor bracket (opening). Matches:@tie{}@code{\floor}.

@item \lhd
@BES{25C1,} Arrowhead, that is, triangle, pointing left (binary).
@value{NeedsAMSSymb} For the normal subgroup symbol you should load
@file{amssymb} and use@tie{}@code{\vartriangleleft} (which is a relation
and so gives better spacing).

@item \ll
@BES{226A,\ll} Much less than (relation).  Similar: much greater
than@tie{}@code{\gg}.

@item \lnot
@BES{00AC,\lnot} Logical negation (ordinary). Synonym:@tie{}@code{\neg}.

@item \longleftarrow
@BES{27F5,\longleftarrow} Long single-line left arrow (relation).  Similar: long
double-line left arrow@tie{}@code{\Longleftarrow}.

@item \longleftrightarrow
@BES{27F7,\longleftrightarrow} Long single-line double-headed arrow (relation).  Similar: long
double-line double-headed arrow@tie{}@code{\Longleftrightarrow}.

@item \longmapsto
@BES{27FC,\longmapsto} Long single-line left arrow starting with vertical bar
(relation).  Similar: shorter version@tie{}@code{\mapsto}.

@item \longrightarrow
@BES{27F6,\longrightarrow} Long single-line right arrow (relation).  Similar: long
double-line right arrow@tie{}@code{\Longrightarrow}.

@item \lor
@BES{2228,\lor} Logical or (binary).  Synonym: wedge@tie{}@code{\wedge}. 

@item \mapsto
@BES{21A6,\mapsto} Single-line left arrow starting with vertical bar (relation).
Similar: longer version@tie{}@code{\longmapsto}.

@item \mho
@BES{2127,} Conductance, half-circle rotated capital omega (ordinary).
@value{NeedsAMSSymb}

@item \mid
@BES{2223,\mid} Single-line vertical bar (relation).  A typical use of
@code{\mid} is for a set @code{\@{\, x \mid x\geq 5 \,\@}}.

Similar: @code{\vert} and@tie{}@code{|} produce the same single-line
vertical bar symbol but without any spacing (they fall in class
ordinary) and you should not use them as relations but instead only as
ordinals, i.e., footnote symbols.  For absolute value, see the entry
for@tie{}@code{\vert} and for norm see the entry for@tie{}@code{\Vert}.

@item \models
@BES{22A8,\models} Entails, or satisfies; double turnstile, short double dash
(relation).  Similar: long double dash@tie{}@code{\vDash}.

@item \mp
@BES{2213,\mp} Minus or plus (relation).

@item \mu
@BES{03BC,\mu} Lowercase Greek letter (ordinary).

@item \nabla
@BES{2207,\nabla} Hamilton's del, or differential, operator (ordinary).

@item \natural
@BES{266E,\natural} Musical natural notation (ordinary).

@item \ne
@BES{2260,\ne} Not equal (relation). Synonym:@tie{}@code{\neq}.

@item \nearrow
@BES{2197,\nearrow} North-east arrow (relation).

@item \neg
@BES{00AC,\neg} Logical negation (ordinary).
Synonym:@tie{}@code{\lnot}. Sometimes instead used for
negation:@tie{}@code{\sim}.

@item \neq
@BES{2260,\neq} Not equal (relation). Synonym:@tie{}@code{\ne}.

@item \ni
@BES{220B,\ni} Reflected membership epsilon; has the member
(relation). Synonym:@tie{}@code{\owns}. Similar: is a member
of@tie{}@code{\in}.

@item \not
@c the "@ "s put in spaces so the not slash doesn't hit the next char.
@BES{0020,\not}@ @ @ @ Long solidus, or slash, used to overstrike a
following operator (relation).

Many negated operators are available that don't require @code{\not},
particularly with the @file{amssymb} package. For example, @code{\notin}
is typographically preferable to @code{\not\in}.

@item \notin
@BES{2209,\notin} Not an element of (relation).  Similar: not subset
of@tie{}@code{\nsubseteq}.

@item \nu
@BES{03BD,\nu} Lowercase Greek letter (ordinary).

@item \nwarrow
@BES{2196,\nwarrow} North-west arrow (relation).

@item \odot
@BES{2299,\odot} Dot inside a circle (binary).  Similar: variable-sized
operator@tie{}@code{\bigodot}.

@item \oint
@BES{222E,\oint} Contour integral, integral with circle in the middle
(operator).

@item \Omega
@BES{03A9,\Omega} uppercase Greek letter (ordinary).

@item \omega
@BES{03C9,\omega} Lowercase Greek letter (ordinary).

@item \ominus
@BES{2296,\ominus} Minus sign, or dash, inside a circle (binary).

@item \oplus
@BES{2295,\oplus} Plus sign inside a circle (binary).  Similar: variable-sized
operator@tie{}@code{\bigoplus}.

@item \oslash
@BES{2298,\oslash} Solidus, or slash, inside a circle (binary).

@item \otimes
@BES{2297,\otimes} Times sign, or cross, inside a circle (binary).  Similar:
variable-sized operator@tie{}@code{\bigotimes}.

@item \owns
@BES{220B,\owns} Reflected membership epsilon; has the member
(relation). Synonym:@tie{}@code{\ni}. Similar: is a member
of@tie{}@code{\in}.

@item \parallel
@BES{2225,\parallel} Parallel (relation). Synonym:@tie{}@code{\|}.

@item \partial
@BES{2202,\partial} Partial differential (ordinary).

@item \perp
@BES{27C2,\perp} Perpendicular (relation).  Similar:@tie{}@code{\bot} uses the
same glyph but the spacing is different because it is in the class
ordinary.

@item \phi
@BES{03D5,\phi} Lowercase Greek letter (ordinary).  The variant form is
@code{\varphi}@tie{}@BES{03C6,\varphi}.

@item \Pi
@BES{03A0,\Pi} uppercase Greek letter (ordinary).

@item \pi
@BES{03C0,\pi} Lowercase Greek letter (ordinary).  The variant form is
@code{\varpi}@tie{}@BES{03D6,\varpi}.

@item \pm
@BES{00B1,\pm} Plus or minus (binary).

@item \prec
@BES{227A,\prec} Precedes (relation). Similar: less than@tie{}@code{<}.

@item \preceq
@BES{2AAF,\preceq} Precedes or equals (relation). Similar: less than or
equals@tie{}@code{\leq}.

@item \prime
@BES{2032,\prime} Prime, or minute in a time expression (ordinary).
Typically used as a superscript: @code{$f^\prime$}; @code{$f^\prime$}
and @code{$f'$} produce the same result.  An advantage of the second
is that @code{$f'''$} produces the desired symbol, that is, the same
result as @code{$f^@{\prime\prime\prime@}$}, but uses rather less
typing.  You can only use @code{\prime} in math mode.  Using the right
single quote@tie{}@code{'} in text mode produces a different character
(apostrophe).

@item \prod
@BES{220F,\prod} Product (operator).

@item \propto
@BES{221D,\propto} Is proportional to (relation)

@item \Psi
@BES{03A8,\Psi} uppercase Greek letter (ordinary).

@item \psi
@BES{03C8,\psi} Lowercase Greek letter (ordinary).

@item \rangle
@BES{27E9,\rangle} Right angle, or sequence, bracket (closing).
Similar: greater than@tie{}@code{>}. Matches:@code{\langle}.

@item \rbrace
@BES{007D,\rbrace} Right curly brace
(closing). Synonym:@tie{}@code{\@}}. Matches@tie{}@code{\lbrace}.

@item \rbrack
@BES{005D,\rbrack} Right square bracket
(closing). Synonym:@tie{}@code{]}. Matches@tie{}@code{\lbrack}.

@item \rceil
@BES{2309,\rceil} Right ceiling bracket (closing). Matches@tie{}@code{\lceil}.

@item \Re
@BES{211C,\Re} Real part, real numbers, cursive capital R (ordinary). Related:
double-line, or blackboard bold, R@tie{}@code{\mathbb@{R@}}; to access
this, load the @file{amsfonts} package.

@item \restriction
@BES{21BE,} Restriction of a function (relation). Synonym:
@code{\upharpoonright}.  @value{NeedsAMSSymb}

@item \revemptyset
@BES{29B0,} Reversed empty set symbol (ordinary).  Related:
@code{\varnothing}. @value{NeedsSTIX}

@item \rfloor
@BES{230B,\rfloor} Right floor bracket, a right square bracket with the top cut
off (closing). Matches@tie{}@code{\lfloor}.

@item \rhd
@BES{25C1,} Arrowhead, that is, triangle, pointing right (binary).
@value{NeedsAMSSymb} For the normal subgroup symbol you should instead
load @file{amssymb} and use@tie{}@code{\vartriangleright} (which is a
relation and so gives better spacing).

@item \rho
@BES{03C1,\rho} Lowercase Greek letter (ordinary).  The variant form is
@code{\varrho}@tie{}@BES{03F1,\varrho}.

@item \Rightarrow
@BES{21D2,\Rightarrow} Implies, right-pointing double line arrow
(relation). Similar: right single-line arrow@tie{}@code{\rightarrow}.

@item \rightarrow
@BES{2192,\rightarrow} Right-pointing single line arrow (relation).
Synonym:@tie{}@code{\to}. Similar: right double line
arrow@tie{}@code{\Rightarrow}.

@item \rightharpoondown
@BES{21C1,\rightharpoondown} Right-pointing harpoon with barb below
the line (relation). 

@item \rightharpoonup
@BES{21C0,\rightharpoonup} Right-pointing harpoon with barb above the
line (relation).

@item \rightleftharpoons
@BES{21CC,\rightleftharpoons} Right harpoon up above left harpoon down
(relation).

@item \searrow
@BES{2198,\searrow} Arrow pointing southeast (relation).

@item \setminus
@BES{29F5,\setminus} Set difference, reverse solidus or reverse slash,
like \ (binary). Similar: backslash@tie{}@code{\backslash} and also
@code{\textbackslash} outside of math mode.

@item \sharp
@BES{266F,\sharp} Musical sharp (ordinary).

@item \Sigma
@BES{03A3,\Sigma} uppercase Greek letter (ordinary).

@item \sigma
@BES{03C3,\sigma} Lowercase Greek letter (ordinary). The variant form is
@code{\varsigma}@tie{}@BES{03C2,\varsigma}.

@item \sim
@BES{223C,\sim} Similar, in a relation (relation).

@item \simeq
@BES{2243,\simeq} Similar or equal to, in a relation (relation).

@item \smallint
@BES{222B,\smallint} Integral sign that does not change to a larger size in a
display (operator).

@item \smile
@BES{2323,\smile} Upward curving arc, smile (ordinary).

@item \spadesuit
@BES{2660,\spadesuit} Spade card suit (ordinary).

@item \sqcap
@BES{2293,\sqcap} Square intersection symbol (binary). Similar:
intersection@tie{}@code{cap}.

@item \sqcup
@BES{2294,\sqcup} Square union symbol (binary). Similar:
union@tie{}@code{cup}. Related: variable-sized
operator@tie{}@code{\bigsqcup}.

@item \sqsubset
@BES{228F,} Square subset symbol (relation). Similar:
subset@tie{}@code{\subset}. @value{NeedsAMSSymb}

@item \sqsubseteq
@BES{2291,\sqsubseteq} Square subset or equal symbol (binary). Similar: subset or
equal to@tie{}@code{\subseteq}.

@item \sqsupset
@BES{2290,} Square superset symbol (relation). Similar:
superset@tie{}@code{\supset}. @value{NeedsAMSSymb}

@item \sqsupseteq
@BES{2292,\sqsupseteq} Square superset or equal symbol (binary).
Similar: superset or equal@tie{}@code{\supseteq}.

@item \star
@BES{22C6,\star} Five-pointed star, sometimes used as a general binary
operation but sometimes reserved for cross-correlation (binary).
Similar: the synonyms asterisk@tie{}@code{*} and @code{\ast}, which
are six-pointed, and more often appear as a superscript or subscript,
as with the Kleene star.

@item \subset
@BES{2282,\subset} Subset (occasionally, is implied by) (relation).

@item \subseteq
@BES{2286,\subseteq} Subset or equal to (relation).

@item \succ
@BES{227B,\succ} Comes after, succeeds (relation). Similar: is less
than@tie{}@code{>}.

@item \succeq
@BES{2AB0,\succeq} Succeeds or is equal to (relation). Similar: less
than or equal to@tie{}@code{\leq}.

@item \sum
@BES{2211,\sum} Summation (operator). Similar: Greek capital
sigma@tie{}@code{\Sigma}.

@item \supset
@BES{2283,\supset} Superset (relation).

@item \supseteq
@BES{2287,\supseteq} Superset or equal to (relation).

@item \surd
@BES{221A,\surd} Radical symbol (ordinary).  The @LaTeX{} command
@code{\sqrt@{...@}} typesets the square root of the argument, with a bar
that extends to cover the argument.

@item \swarrow
@BES{2199,\swarrow} Southwest-pointing  arrow (relation).

@item \tau
@BES{03C4,\tau} Lowercase Greek letter (ordinary).

@item \theta
@BES{03B8,\theta} Lowercase Greek letter (ordinary). The variant form is
@code{\vartheta}@tie{}@BES{03D1,\vartheta}.

@item \times
@BES{00D7,\times} Primary school multiplication sign (binary). See
also@tie{}@code{\cdot}.

@item \to
@BES{2192,\to} Right-pointing single line arrow (relation).
Synonym:@tie{}@code{\rightarrow}.

@item \top
@BES{22A4,} Top, greatest element of a partially ordered set
(ordinary). See also@tie{}@code{\bot}.

@item \triangle
@BES{25B3,\triangle} Triangle (ordinary).

@item \triangleleft
@BES{25C1,\triangleleft} Not-filled triangle pointing left
(binary). Similar:@tie{}@code{\lhd}. For the normal subgroup symbol you
should load @file{amssymb} and use@tie{}@code{\vartriangleleft} (which
is a relation and so gives better spacing).

@item \triangleright
@BES{25B7,\triangleright} Not-filled triangle pointing right
(binary). For the normal subgroup symbol you should instead load
@file{amssymb} and use@tie{}@code{\vartriangleright} (which is a
relation and so gives better spacing).

@item \unlhd
@BES{22B4,} Left-pointing not-filled underlined arrowhead, that is,
triangle, with a line under (binary). @value{NeedsAMSSymb} For the
normal subgroup symbol load @file{amssymb} and
use@tie{}@code{\vartrianglelefteq} (which is a relation and so gives
better spacing).

@item \unrhd
@BES{22B5,} Right-pointing not-filled underlined arrowhead, that is,
triangle, with a line under (binary). @value{NeedsAMSSymb} For the
normal subgroup symbol load @file{amssymb} and
use@tie{}@code{\vartrianglerighteq} (which is a relation and so gives
better spacing).

@item \Uparrow
@BES{21D1,\Uparrow} Double-line upward-pointing arrow
(relation). Similar: single-line up-pointing
arrow@tie{}@code{\uparrow}.

@item \uparrow
@BES{2191,\uparrow} Single-line upward-pointing arrow, diverges
(relation). Similar: double-line up-pointing
arrow@tie{}@code{\Uparrow}.

@item \Updownarrow
@BES{21D5,\Updownarrow} Double-line upward-and-downward-pointing arrow
(relation). Similar: single-line upward-and-downward-pointing
arrow@tie{}@code{\updownarrow}.

@item \updownarrow
@BES{2195,\updownarrow} Single-line upward-and-downward-pointing arrow
(relation). Similar: double-line upward-and-downward-pointing
arrow@tie{}@code{\Updownarrow}.

@item \upharpoonright
@BES{21BE,} Up harpoon, with barb on right side
(relation). Synonym:@tie{}@code{@backslashchar{}restriction}.
@value{NeedsAMSSymb}

@item \uplus
@BES{228E,\uplus} Multiset union, a union symbol with a plus symbol in
the middle (binary). Similar: union@tie{}@code{\cup}. Related:
variable-sized operator@tie{}@code{\biguplus}.

@item \Upsilon
@BES{03A5,\Upsilon} uppercase Greek letter (ordinary).

@item \upsilon
@BES{03C5,\upsilon} Lowercase Greek letter (ordinary).

@item \varepsilon
@BES{03B5,\varepsilon} Small letter script epsilon (ordinary).  This is
more widely used in mathematics than the non-variant lunate epsilon form
@code{\epsilon}@tie{}@BES{03F5,\epsilon}. Related: set
membership@tie{}@code{\in}.

@item \vanothing
@BES{2205,} Empty set symbol. Similar: @code{\emptyset}. Related:
@code{\revemptyset}. @value{NeedsAMSSymb}

@item \varphi
@BES{03C6,\varphi} Variant on the lowercase Greek letter (ordinary).
The non-variant form is @code{\phi}@tie{}@BES{03D5,\phi}.

@item \varpi
@BES{03D6,\varpi} Variant on the lowercase Greek letter (ordinary).
The non-variant form is @code{\pi}@tie{}@BES{03C0,\pi}.

@item \varrho
@BES{03F1,\varrho} Variant on the lowercase Greek letter (ordinary).
The non-variant form is @code{\rho}@tie{}@BES{03C1,\rho}.

@item \varsigma
@BES{03C2,\varsigma} Variant on the lowercase Greek letter
(ordinary).  The non-variant form is
@code{\sigma}@tie{}@BES{03C3,\sigma}.

@item \vartheta
@BES{03D1,\vartheta} Variant on the lowercase Greek letter
(ordinary).  The non-variant form is
@code{\theta}@tie{}@BES{03B8,\theta}.

@item \vdash
@BES{22A2,\vdash} Provable; turnstile, vertical and a dash
(relation). Similar: turnstile rotated a
half-circle@tie{}@code{\dashv}.

@item \vee
@BES{2228,\vee} Logical or; a downwards v shape (binary). Related:
logical and@tie{}@code{\wedge}. Similar: variable-sized
operator@tie{}@code{\bigvee}.

@item \Vert
@BES{2016,\Vert} Vertical double bar (ordinary). Similar: vertical single
bar@tie{}@code{\vert}.

For a norm symbol, you can use the @file{mathtools} package and put in
your preamble
@code{\DeclarePairedDelimiter\norm@{\lVert@}@{\rVert@}}. This gives you
three command variants for double-line vertical bars that are correctly
horizontally spaced: if in the document body you write the starred
version @code{$\norm*@{M^\perp@}$} then the height of the vertical bars
will match the height of the argument, whereas with
@code{\norm@{M^\perp@}} the bars do not grow with the height of the
argument but instead are the default height, and @code{\norm[@var{size
command}]@{M^\perp@}} also gives bars that do not grow but are set to
the size given in the @var{size command}, e.g., @code{\Bigg}.

@item \vert
@BES{007C,\vert} Single line vertical bar (ordinary). Similar: double-line
vertical bar@tie{}@code{\Vert}. For such that, as in the definition of a 
set, use@tie{}@code{\mid} because it is a relation.  

For absolute value you can use the @file{mathtools} package and in your
preamble put
@code{\DeclarePairedDelimiter\abs@{\lvert@}@{\rvert@}}. This gives you
three command variants for single-line vertical bars that are correctly
horizontally spaced: if in the document body you write the starred
version @code{$\abs*@{\frac@{22@}@{7@}@}$} then the height of the
vertical bars will match the height of the argument, whereas with
@code{\abs@{\frac@{22@}@{7@}@}} the bars do not grow with the height of
the argument but instead are the default height, and
@code{\abs[@var{size command}]@{\frac@{22@}@{7@}@}} also gives bars that
do not grow but are set to the size given in the @var{size command},
e.g., @code{\Bigg}.

@item \wedge
@BES{2227,\wedge} Logical and (binary).  Synonym:@tie{}@code{\land}.  See also
logical or @code{\vee}. Similar: variable-sized
operator@tie{}@code{\bigwedge}.

@item \wp
@BES{2118,\wp} Weierstrass p (ordinary).

@item \wr
@BES{2240,\wr} Wreath product (binary).

@item \Xi
@BES{039E,\Xi} uppercase Greek letter (ordinary).

@item \xi
@BES{03BE,\xi} Lowercase Greek letter (ordinary).

@item \zeta
@BES{03B6,\zeta} Lowercase Greek letter (ordinary).

@end ftable

The following symbols are most often used in plain text but @LaTeX{}
provides versions to use in mathematical text.

@ftable @code
@item \mathdollar
Dollar sign in math mode: $.

@item \mathparagraph
Paragraph sign (pilcrow) in math mode, @BES{00B6,\P}.

@item \mathsection
Section sign in math mode @BES{00A7,\S}.

@item \mathsterling
Sterling sign in math mode: @pounds{}.

@item \mathunderscore
Underscore in math mode: _.

@end ftable

@menu
* Blackboard bold::            Doublestruck characters.
* Calligraphic::               Cursive characters.
* \boldmath & \unboldmath::    Symbols in boldface.
* Dots::                       Ellipses, etc.
@end menu


@node Blackboard bold
@subsection Blackboard bold

@cindex blackboard bold
@cindex doublestruck

Synopsis:

@example
\usepackage@{amssymb@}   % in preamble
  ... 
\mathbb@{@var{uppercase-letter}@}
@end example

Provide blackboard bold symbols, sometimes also known as doublestruck
letters, used to denote number sets such as the natural numbers, the
integers, etc.

Here 

@example
\( \forall n \in \mathbb@{N@}, n^2 \geq 0 \)
@end example

@noindent
the @code{\mathbb@{N@}} gives blackboard bold symbol @BES{2115,}
representing the natural numbers.

If you use other than an uppercase letter then you do not get an error
but you get strange results, including unexpected characters.

There are packages that give access to symbols other than just the
capital letters; look on CTAN.


@node Calligraphic
@subsection Calligraphic

@cindex calligraphic fonts
@cindex script fonts
@cindex fonts, script

Synopsis:

@example
\mathcal@{@var{uppercase-letters}@}
@end example

Use a script-like font.

In this example the graph identifier is output in a cursive font.

@example
Let the graph be \( \mathcal@{G@} \).
@end example

If you use something other than an uppercase letter then you do not get
an error.  Instead you get unexpected output.  For instance,
@code{\mathcal@{g@}} outputs a close curly brace symbol, while
@code{\mathcal@{+@}} outputs a plus sign.  


@node \boldmath & \unboldmath
@subsection @code{\boldmath} & @code{\unboldmath}

@cindex boldface mathematics
@cindex symbols, boldface
@findex \boldmath
@findex \unboldmath

Synopsis (used in paragraph mode or LR mode):

@example
\boldmath \( @var{math} \)
@end example

@noindent
or

@example
\unboldmath \( @var{math} \)
@end example

@findex \boldmath
@findex \unboldmath
Declarations to change the letters and symbols in @var{math} to be in
a bold font, or to countermand that and bring back the regular
(non-bold) default. They must be used when not in math mode or display
math mode (@pxref{Modes}). Both commands are fragile
(@pxref{\protect}).

In this example each @code{\boldmath} command takes place inside an
@code{\mbox},

@example
we have $\mbox@{\boldmath \( v \)@} = 5\cdot\mbox@{\boldmath \( u \)$@}$
@end example

@noindent
which means @code{\boldmath} is only called in a text mode, here LR
mode, and explains why @LaTeX{} must switch to math mode to set @code{v}
and @code{u}.

If you use either command inside math mode, as with @code{Trouble: \(
\boldmath x \)}, then you get something like @samp{LaTeX Font Warning:
Command \boldmath invalid in math mode on input line 11} and @samp{LaTeX
Font Warning: Command \mathversion invalid in math mode on input line
11}.

@PkgIndex{bm}
There are many issues with @code{\boldmath}.  New documents should use
the @file{bm} package provided by the @LaTeX{} Project team.  A complete
description is outside the scope of this document (see the full
documentation on CTAN) but even this small example

@example
\usepackage@{bm@}   % in preamble
...
we have $\bm@{v@} = 5\cdot\bm@{u@}$
@end example

@noindent
shows that it is an improvement over @code{\boldmath}.


@node Dots
@subsection Dots, horizontal or vertical

@cindex ellipses
@cindex dots

Ellipses are the three dots (usually three) indicating that a pattern
continues.

@example
\begin@{array@}@{cccc@}
  a_@{0,0@}    &a_@{0,1@}   &a_@{0,2@} &\ldots \\
  a_@{1,0@}    &\ddots                     \\
  \vdots
\end@{array@}
@end example

@LaTeX{} provides these.

@ftable @code
@anchor{ellipses cdots}
@item \cdots
Horizontal ellipsis with the dots raised to the center of the line, as
in @BES{22EF,\cdots}.  Used as: @code{\( a_0\cdot a_1\cdots a_@{n-1@}
\)}.

@anchor{ellipses ddots}
@item \ddots
Diagonal ellipsis, @BES{22F1,\ddots}.  See the above array example for a
usage.

@anchor{ellipses ldots}
@item \ldots
Ellipsis on the baseline, @BES{2026,\ldots}.  Used as: @code{\(
x_0,\ldots x_@{n-1@} \)}.  Another example is the above array example. A
synonym is @code{\mathellipsis}.  A synonym from the @file{amsmath}
package is @code{\hdots}.

You can also use this command outside of mathematical text, as in
@code{The gears, brakes, \ldots@{@} are all broken}.  (In a paragraph
mode or LR mode a synonym for @code{\ldots} is @code{\dots}.)

@anchor{ellipses vdots}
@item \vdots
Vertical ellipsis, @BES{22EE,\vdots}.  See the above array example for a
usage.

@end ftable

@PkgIndex{amsmath}
The @file{amsmath} package has the command @code{\dots} to semantically
mark up ellipses.  This example produces two different-looking outputs
for the first two uses of the @code{\dots} command.

@example
\usepackage@{amsmath@}  % in preamble
  ...
Suppose that \( p_0, p_1, \dots, p_@{n-1@} \) lists all of the primes.
Observe that \( p_0\cdot p_1 \dots \cdot p_@{n-1@} +1 \) is not a
  multiple of any \( p_i \).
Conclusion: there are infinitely many primes \( p_0, p_1, \dotsc \).
@end example

@noindent
In the first line @LaTeX{} looks to the comma following @code{\dots} to
determine that it should output an ellipsis on the baseline.  The second
line has a @code{\cdot} following @code{\dots} so @LaTeX{} outputs an
ellipsis that is on the math axis, vertically centered.  However, the
third usage has no follow-on character so you have to tell @LaTeX{} what
to do.  You can use one of the commands: @code{\dotsc} if you need the
ellipsis appropriate for a comma following, @code{\dotsb} if you need
the ellipses that fits when the dots are followed by a binary operator
or relation symbol, @code{\dotsi} for dots with integrals, or
@code{\dotso} for others.


@node Math functions
@section Math functions

@cindex math functions
@cindex functions, math

These commands produce roman function names in math mode with proper
spacing.

@ftable @code
@item \arccos
Inverse cosine
@iftex
@math{\arccos}
@end iftex

@item \arcsin
Inverse sine
@iftex
@math{\arcsin}
@end iftex

@item \arctan
Inverse tangent
@iftex
@math{\arctan}
@end iftex

@item \arg
Angle between the real axis and a point in the complex plane
@iftex
@math{\arg}
@end iftex

@item \bmod
Binary modulo operator, used as in @code{\( 5\bmod 3=2 \)}
@iftex
@math{5 \bmod 3}
@end iftex

@item \cos
Cosine
@iftex
@math{\cos}
@end iftex

@item \cosh
Hyperbolic cosine
@iftex
@math{\cosh}
@end iftex

@item \cot
Cotangent
@iftex
@math{\cot}
@end iftex

@item \coth
Hyperbolic cotangent
@iftex
@math{\coth}
@end iftex

@item \csc
Cosecant
@iftex
@math{\csc}
@end iftex

@item \deg
Degrees
@iftex
@math{\deg}
@end iftex

@item \det
Determinant
@iftex
@math{\det}
@end iftex

@item \dim
Dimension
@iftex
@math{\dim}
@end iftex

@item \exp
Exponential
@iftex
@math{\exp}
@end iftex

@item \gcd
Greatest common divisor
@iftex
@math{\gcd}
@end iftex

@item \hom
Homomorphism
@iftex
@math{\hom}
@end iftex

@item \inf
Infinum
@iftex
@math{\inf}
@end iftex

@item \ker
Kernel
@iftex
@math{\ker}
@end iftex

@item \lg
Base 2 logarithm
@iftex
@math{\lg}
@end iftex

@item \lim
Limit
@iftex
@math{\lim}
@end iftex

@item \liminf
Limit inferior
@iftex
@math{\liminf}
@end iftex

@item \limsup
Limit superior
@iftex
@math{\limsup}
@end iftex

@item \ln
Natural logarithm
@iftex
@math{\ln}
@end iftex

@item \log
Logarithm
@iftex
@math{\log}
@end iftex

@item \max
Maximum
@iftex
@math{\max}
@end iftex

@item \min
Minimum
@iftex
@math{\min}
@end iftex

@item \pmod
Parenthesized modulus, as used in @code{\( 5\equiv 2\pmod 3 \)}
@iftex
@math{5\equiv 2\pmod 3}
@end iftex

@item \Pr
Probability
@iftex
@math{\Pr}
@end iftex

@item \sec
Secant
@iftex
@math{\sec}
@end iftex

@item \sin
Sine
@iftex
@math{\sin}
@end iftex

@item \sinh
Hyperbolic sine
@iftex
@math{\sinh}
@end iftex

@item \sup
@iftex
Supremum
@iftex
@math{\mathop {\rm sup}}
@end iftex
@ifnottex
sup
@end ifnottex
@c don't try to use \sup with dvi/pdf output since that turned into a
@c Texinfo command and it's not worth hassling with different versions
@c when it's just three roman letters anyway.

@item \tan
Tangent
@iftex
@math{\tan}
@end iftex

@item \tanh
Hyperbolic tangent
@iftex
@math{\tanh}
@end iftex

@end ftable

@PkgIndex{amsmath}
The @file{amsmath} package adds improvements on some of these, and also
allows you to define your own.  The full documentation is on CTAN, but
briefly, you can define an identity operator with
@code{\DeclareMathOperator@{\identity@}@{id@}} that is like the ones
above but prints as @samp{id}.  The starred form
@code{\DeclareMathOperator*@{\op@}@{op@}} sets any limits above and
below, as is traditional with @code{\lim}, @code{\sup}, or @code{\max}.


@node Math accents
@section Math accents

@cindex math accents
@cindex accents, mathematical

@LaTeX{} provides a variety of commands for producing accented letters
in math.  These are different from accents in normal text
(@pxref{Accents}).

@ftable @code
@item \acute
@cindex acute accent, math
Math acute accent
@iftex
@math{\acute{x}}.
@end iftex

@item \bar
@cindex bar-over accent, math
@cindex macron accent, math
Math bar-over accent
@iftex
@math{\bar{x}}
@end iftex

@item \breve
@cindex breve accent, math
Math breve accent
@iftex
@math{\breve{x}}
@end iftex

@item \check
@cindex check accent, math
@cindex h@'a@v{c}ek accent, math
Math h@'a@v{c}ek (check) accent
@iftex
@math{\check{x}}
@end iftex

@item \ddot
@cindex double dot accent, math
Math dieresis accent
@iftex
@math{\ddot{x}}
@end iftex

@item \dot
@cindex overdot accent, math
@cindex dot over accent, math
Math dot accent
@iftex
@math{\dot{x}}
@end iftex

@item \grave
@cindex grave accent, math
Math grave accent
@iftex
@math{\grave{x}}
@end iftex

@item \hat
@cindex hat accent, math
@cindex circumflex accent, math
Math hat (circumflex) accent
@iftex
@math{\hat{x}}
@end iftex

@item \mathring
@cindex ring accent, math
Math ring accent  @c don't bother implementing in texinfo
@iftex
@ringaccent{x}
@end iftex

@item \tilde
@cindex tilde accent, math
Math tilde accent
@iftex
@math{\tilde{x}}
@end iftex

@item \vec
@cindex vector symbol, math
Math vector symbol
@iftex
@math{\vec{x}}
@end iftex

@item \widehat
@cindex wide hat accent, math
Math wide hat accent
@iftex
@math{\widehat{x+y}}
@end iftex

@item \widetilde
@cindex wide tilde accent, math
Math wide tilde accent
@iftex
@math{\widetilde{x+y}}
@end iftex

@end ftable

When you are putting an accent on an i or a j, the tradition is to use
one without a dot, @code{\imath} or @code{jmath} (@pxref{Math symbols}).


@node Over- and Underlining
@section Over- and Underlining

@cindex overlining
@cindex underlining

@LaTeX{} provides commands for making overlines or underlines, or
putting braces over or under some material.

@ftable @code

@item \underline@{@var{text}@}
Underline @var{text}.  Works inside math mode, and outside.
@ifset HAS-MATH
The result of @code{\underline@{xyz@}} is @math{\underline{xyz}}.
@end ifset
The line is always completely below the text, taking account of
descenders, so in @code{\(\underline@{y@}\)} the line is lower than in
@code{\(\underline@{x@}\)}.  This command is fragile (@pxref{\protect}).

@PkgIndex{ulem}
Note that the package @file{ulem} does text mode underlining and allows
line breaking as well as a number of other features.  See the
documentation on CTAN.  See also@tie{}@ref{\hrulefill & \dotfill} for
producing a line, for such things as a signature.
        
@item \overline@{@var{text}@}
Put a horizontal line over @var{text}.  Works inside math mode, and
outside.  For example, @code{\overline@{x+y@}}.
@ifset HAS-MATH
The result looks like: @math{\overline{x+y}}.
@end ifset
Note that this differs from the command @code{\bar} (@pxref{Math
accents}).

@item \underbrace@{@var{math}@}
Put a brace under @var{math}. For example, this
@code{(1-\underbrace@{1/2)+(1/2@}-1/3)} emphasizes the telescoping part.
@ifset HAS-MATH
The result looks like this: @math{(1-\underbrace{1/2)+(1/2}-1/3)}.
@end ifset
Attach text to the brace by using subscript, @code{_}, or superscript,
@code{^}, as here.

@example
\begin@{displaymath@}
  1+1/2+\underbrace@{1/3+1/4@}_@{>1/2@}+
       \underbrace@{1/5+1/6+1/7+1/8@}_@{>1/2@}+\cdots
\end@{displaymath@}
@end example

The superscript appears on top of the expression, and so can look
unconnected to the underbrace.

@item \overbrace@{@var{math}@}
Put a brace over @var{math}, as with
@code{\overbrace@{x+x+\cdots+x@}^@{\mbox@{\(k\) times@}@}}.  See also
@code{\underbrace}.

@end ftable

@PkgIndex{mathtools}
The package @file{mathtools} adds an over- and underbrace, as well as
some improvements on the braces.  See the documentation on CTAN.


@node Spacing in math mode
@section Spacing in math mode

@cindex spacing within math mode
@cindex math mode, spacing

When typesetting mathematics, @LaTeX{} puts in spacing according to the
normal rules for mathematics texts.  If you enter @code{y=m x} then
@LaTeX{} ignores the space and in the output the m is next to the x,
as @math{y=mx}.

But @LaTeX{}'s rules sometimes need tweaking.  For example, in an
integral the tradition is to put a small extra space between the
@code{f(x)} and the @code{dx}, here done with the @code{\,} command.

@example
\int_0^1 f(x)\,dx
@end example

@LaTeX{} provides the commands that follow for use in math mode.  Many
of these spacing definitions are expressed in terms of the math unit
@dfn{mu}.  It is defined as 1/18@dmn{em}, where the em is taken from the
current math symbols family (@pxref{Units of length}).  Thus, a
@code{\thickspace} is something like 5/18 times the width of
a@tie{}@samp{M}.

@table @code
@item \;
@findex \;
@findex \thickspace
@anchor{spacing in math mode thickspace}
Synonym: @code{\thickspace}.  Normally @code{5.0mu plus 5.0mu}.  Math
mode only.

@item \:
@itemx \>
@findex \:
@findex \>
@findex \medspace
@anchor{spacing in math mode medspace}
Synonym: @code{\medspace}.  Normally @code{4.0mu plus 2.0mu minus 4.0mu}.
Math mode only.

@item \,
@findex \,
@findex \thinspace
@cindex thin space
@anchor{Spacing in math mode/\thinspace}
@anchor{spacing in math mode thinspace}
Synonym: @code{\thinspace}.  Normally @code{3mu}, which is 1/6@dmn{em}.
Can be used in both math mode and text mode (@pxref{\thinspace &
\negthinspace}).

This space is widely used, for instance between the function and the
infinitesimal in an integral @code{\int f(x)\,dx} and, if an author does
this, before punctuation in a displayed equation.

@example
The antiderivative is
\begin@{equation@}
  3x^@{-1/2@}+3^@{1/2@}\,.
\end@{equation@}
@end example

@item \!
@findex \!
@findex \negthinspace
@cindex thin space, negative
@anchor{spacing in math mode negthinspace}
A negative thin space. Normally @code{-3mu}.  The @code{\!} command is
math mode only but the @code{\negthinspace} command is available for
text mode (@pxref{\thinspace & \negthinspace}).

@item \quad
@cindex quad
@findex \quad
@anchor{spacing in math mode quad}
This is 18@dmn{mu}, that is, 1@dmn{em}. This is often used for space
surrounding equations or expressions, for instance for the space between
two equations inside a @code{displaymath} environment.  It is available
in both text and math mode.

@item \qquad
@findex \qquad
@anchor{spacing in math mode qquad}
A length of 2 quads, that is, 36@dmn{mu} = 2@dmn{em}.  It is available in
both text and math mode.
@end table

@menu
* \smash::                            Eliminate height or depth of a subformula.
* \phantom & \vphantom & \hphantom::  Make empty box with the same size as the argument.
@end menu


@node \smash
@subsection @code{\smash}

@cindex vertical spacing, math mode
@cindex math mode, vertical space

Synopsis:

@example
\smash@{@var{subformula}@}
@end example

Typeset @var{subformula} as if its height and depth were zero.

In this example the exponential is so tall that without the
@code{\smash} command @LaTeX{} would separate its line from the line
above it, and the uneven line spacing might be unsightly.

@example
To compute the tetration $\smash@{2^@{2^@{2^2@}@}@}$,
evaluate from the top down, as $2^@{2^4@}=2^@{16@}=65536$.
@end example

(Because of the @code{\smash} the printed expression could run into the
line above so you may want to wait until the final version of the
document to make such adjustments.)

This pictures the effect of @code{\smash} by using @code{\fbox} to
surround the box that @LaTeX{} will put on the line.  The
@code{\blackbar} command makes a bar extending from 10@tie{}points below
the baseline to 20@tie{}points above.

@example
\newcommand@{\blackbar@}@{\rule[-10pt]@{5pt@}@{30pt@}@}
\fbox@{\blackbar@}
\fbox@{\smash@{\blackbar@}@}
@end example

The first box that @LaTeX{} places is 20@tie{}points high and
10@tie{}points deep.  But the second box is treated by @LaTeX{} as
having zero height and zero depth, despite that the ink printed on the
page still extends well above and below the line.

The @code{\smash} command appears often in mathematics to adjust the
size of an element that surrounds a subformula.  Here the first radical
extends below the baseline while the second lies just on the baseline.

@example
\begin@{equation@}
\sqrt@{\sum_@{0\leq k< n@} f(k)@}
\sqrt@{\vphantom@{\sum@}\smash@{\sum_@{0\leq k< n@}@} f(k)@}
\end@{equation@}
@end example

Note the use of @code{\vphantom} to give the @code{\sqrt} command an
argument with the height of the @code{\sum} (@pxref{\phantom & \vphantom
& \hphantom}).

While most often used in mathematics, the @code{\smash} command can
appear in other contexts.  However, it doesn't change into horizontal
mode.  So if it starts a paragraph then you should first put a
@code{\leavevmode}, as in the bottom line below.

@example
xxx xxx xxx

\smash@{yyy@}  % no paragraph indent

\leavevmode\smash@{zzz@}  % usual paragraph indent
@end example

@PkgIndex{mathtools}
The package @code{mathtools} has operators that provide even finer
control over smashing a subformula box.


@node \phantom & \vphantom & \hphantom
@subsection @code{\phantom} & @code{\vphantom} & @code{\hphantom}

@cindex spacing, math mode
@cindex horizontal spacing
@cindex vertical spacing
@cindex math mode, spacing
@cindex invisible character
@cindex character, invisible

Synopsis:

@example
\phantom@{@var{subformula}@}
@end example

or

@example
\vphantom@{@var{subformula}@}
@end example

or

@example
\hphantom@{@var{subformula}@}
@end example

The @code{\phantom} command creates a box with the same height, depth,
and width as @var{subformula}, but empty.  That is, this command causes
@LaTeX{} to typeset the box but not its ink.  The @code{\vphantom}
variant also produces an invisible box with the same height and depth as
@var{subformula}, but it has width zero.  And @code{\hphantom} makes a
box with the same width as @var{subformula} but with height and depth
zero.

Without the @code{\vphantom} in this example, the top bars of the two
square roots would be at different heights.

@example
\( \sqrt@{\vphantom@{a^3@}a@}\cdot\sqrt@{a^3@} \)
@end example

The @code{\vphantom@{a^3@}} causes the first @code{\sqrt} to have inside
it a box of the same height as the second @code{\sqrt}, so @LaTeX{}
makes the bars align.

These commands often are combined with @code{\smash}.  @xref{\smash}
for another example of the use of @code{\vphantom}.

@PkgIndex{mathtools}
The three phantom commands appear often but note that @LaTeX{} provides
a suite of other commands to work with box sizes that may be more
convenient, including @code{\makebox} (@pxref{\mbox & \makebox}) as well
as @code{\settodepth} (@pxref{\settodepth}), @code{\settoheight}
(@pxref{\settoheight}), and @code{\settowidth} (@pxref{\settowidth}).
In addition, the @file{mathtools} package has many commands that offer
fine-grained control over spacing.

@PkgIndex{amsmath}
All three commands produce an ordinary box, without any special
mathematics status.  So to do something like attaching a superscript you
should give it such a status, for example with the @code{\operatorname}
command from the package @file{amsmath}.

While most often used in mathematics, these three can appear in other
contexts.  However, they don't cause @LaTeX{} to change into horizontal
mode.  So if one of these starts a paragraph then you should prefix it
with @code{\leavevmode}.


@node Math miscellany
@section Math miscellany

@cindex math miscellany

@LaTeX{} contains a wide variety of mathematics facilities.  Here are
some that don't fit into other categories.

@menu
* Colon character & \colon::    Colon.
* \*::                            Discretionary multiplication.
* \frac::                         Fraction.
* \left & \right::                Paired delimiters.
* \sqrt::                         Radicals.
* \stackrel::                     Text over a relation.
@end menu


@node Colon character & \colon  
@subsection Colon character @code{:} & @code{\colon}

@cindex :
@cindex colon character
@findex :
@findex \colon

Synopsis, one of:

@example
:
\colon
@end example

In mathematics, the colon character, @code{:}, is a relation.

@example
With side ratios \( 3:4 \) and \( 4:5 \), the triangle is right.
@end example

@PkgIndex{amsmath}
@noindent
Ordinary @LaTeX{} defines @code{\colon} to produce the colon character
with the spacing appropriate for punctuation, as in set-builder notation
@code{\@{x\colon 0\leq x<1\@}}.

@PkgIndex{amsmath}
But the widely-used @file{amsmath} package defines @code{\colon} for use
in the definition of functions @code{f\colon D\to C}.  So if you want
the colon character as a punctuation then use @code{\mathpunct@{:@}}.


@node \* 
@subsection @code{\*}

@cindex multiplication, discretionary
@cindex breaks, multiplication discretionary
@cindex line breaks, multiplication discretionary
@cindex discretionary breaks, multiplication
@findex \*

Synopsis:

@example
\*
@end example

A multiplication symbol that allows a line break.  If there is a break
then @LaTeX{} puts a @code{\times} symbol, @BES{00D7,\times}, before
that break.

In @code{\( A_1\* A_2\* A_3\* A_4 \)}, if there is no line break then
@LaTeX{} outputs it as though it were @code{\( A_1 A_2 A_3 A_4 \)}.  If
a line break does happen, for example between the two middle ones, then
@LaTeX{} sets it like @code{\( A_1 A_2 \times \)}, followed by the
break, followed by @code{\( A_3 A_4 \)}.


@node \frac
@subsection @code{\frac} 

@cindex fraction
@findex \frac

Synopsis:

@example
\frac@{@var{numerator}@}@{@var{denominator}@}
@end example

Produces the fraction.  Used as: @code{\begin@{displaymath@}
\frac@{1@}@{\sqrt@{2\pi\sigma@}@} \end@{displaymath@}}.  In inline math
mode it comes out small; see the discussion of @code{\displaystyle}
(@pxref{Math formulas}).


@node \left & \right
@subsection @code{\left} & @code{\right}

@cindex delimiters, paired
@cindex paired delimiters
@cindex matching parentheses
@cindex matching brackets
@cindex null delimiter
@findex \left
@findex \right

Synopsis:

@example
\left @var{delimiter1} ... \right @var{delimiter2}
@end example

Make matching parentheses, braces, or other delimiters.  The delimiters
are sized according to the math they enclose.  This makes a unit vector
surrounded by appropriate-height parentheses.

@example
\begin@{equation@}
  \left(\begin@{array@}@{c@}
    1   \\
    0   \\
  \end@{array@}\right)
@end example

Every @code{\left} must have a matching @code{\right}.  Leaving out the
@code{\left(} in the above gets @samp{Extra \right}.  Leaving off the
@code{\right)} gets @samp{You can't use `\eqno' in math mode}.

However, the two delimiters @var{delimiter1} and @var{delimiter2} need
not match.  A common case is that you want an unmatched brace, as
below. Use a period, @samp{.}, as a null delimiter.

@example
\begin@{equation@}
  f(n)=\left\@{\begin@{array@}@{ll@}
                1             &\mbox@{--if \(n=0\)@} \\
                f(n-1)+3n^2   &\mbox@{--else@}       
       \end@{array@}\right.
\end@{equation@}
@end example

@noindent
Note that to get a curly brace as a delimiter you must prefix it with a
backslash, @code{\@{}.


@node \sqrt
@subsection @code{\sqrt}

@cindex square root
@cindex roots
@cindex radical
@findex \sqrt

Synopsis, one of:

@example
\sqrt@{@var{arg}@}
\sqrt[@var{root-number}]@{@var{arg}@}
@end example

The square root, or optionally other roots, of @var{arg}.  The optional
argument @var{root-number} gives the root, i.e., enter the cube root of
@code{x+y} as @code{\sqrt[3]@{x+y@}}.
@ifset HAS-MATH
It comes out like this: @math{\root 3 \of {x+y}}.
@end ifset
The radical grows with the size of @var{arg} (as the height of the
radical grows, the angle on the leftmost part gets steeper, until for
a large enough @code{arg}, it is vertical).

@LaTeX{} has a separate @code{\surd} character (@pxref{Math symbols}).


@node \stackrel
@subsection @code{\stackrel}

@cindex stack math
@cindex relation, text above
@findex \stackrel

Synopsis, one of:

@example
\stackrel@{@var{text}@}@{@var{relation}@}
@end example

Put @var{text} above @var{relation}.  To put a function name above an
arrow enter @code{\stackrel@{f@}@{\longrightarrow@}}.
@ifset HAS-MATH
 The result looks like this: @math{\buildrel f \over \longrightarrow}.
@end ifset


@node Modes
@chapter Modes

@cindex modes

As @LaTeX{} processes your document, at any point it is in one of six
modes.  They fall into three categories of two each, the horizontal
modes, the math modes, and the vertical modes. Some commands only work
in one mode or another (in particular, many commands only work in one of
the math modes), and error messages will refer to these.

@itemize
@item
@anchor{modes paragraph mode}
@cindex paragraph mode
@dfn{Paragraph mode} is what @LaTeX{} is in when processing ordinary
text.  It breaks the input text into lines and breaks the lines into
pages.  This is the mode @LaTeX{} is in most of the time.

@cindex left-to-right mode
@cindex LR mode
@anchor{modes lr mode}
@dfn{LR mode} (for left-to-right mode; in plain @TeX{} this is called
@dfn{restricted horizontal mode}) is in effect when @LaTeX{} starts
making a box with an @code{\mbox} command.  As in paragraph mode,
@LaTeX{}'s output is a string of words with spaces between them.  Unlike
in paragraph mode, in LR mode @LaTeX{} never starts a new line, it just
keeps going from left to right.  (Although @LaTeX{} will not complain
that the LR box is too long, when it is finished and next tries to put
that box into a line, it could very well complain that the finished LR
box won't fit there.)

@item
@cindex math mode
@anchor{modes math mode} @dfn{Math mode} is when @LaTeX{} is generating
an inline mathematical formula.

@cindex display math mode
@dfn{Display math mode} is when @LaTeX{} is generating a displayed
mathematical formula.  (Displayed formulas differ somewhat from inline
ones.  One example is that the placement of the subscript on @code{\int}
differs in the two situations.)

@item
@cindex vertical mode
@anchor{modes vertical mode}
@dfn{Vertical mode} is when @LaTeX{} is building the list of lines and
other material making the output page.  This is the mode @LaTeX{} is in
when it starts a document.

@cindex internal vertical mode
@anchor{modes internal vertical mode}
@dfn{Internal vertical mode} is in effect when @LaTeX{} starts making a
@code{\vbox}.  This is the vertical analogue of LR mode.

@end itemize

@noindent
For instance, if you begin a @LaTeX{} article with @samp{Let \( x \) be
...} then these are the modes: first @LaTeX{} starts every document in
vertical mode, then it reads the @samp{L} and switches to paragraph
mode, then the next switch happens at the @samp{\(} where @LaTeX{}
changes to math mode, and then when it leaves the formula it pops
back to paragraph mode.

@cindex inner paragraph mode
@cindex outer paragraph mode
@anchor{modes inner paragraph mode}
@anchor{modes outer paragraph mode}
Paragraph mode has two subcases.  If you use a @code{\parbox} command
or a @code{minipage} then @LaTeX{} is put into paragraph mode.  But it
will not put a page break here.  Inside one of these boxes, called a
@dfn{parbox}, @LaTeX{} is in @dfn{inner paragraph mode}.  Its more usual
situation, where it can put page breaks, is @dfn{outer paragraph mode}
(@pxref{Page breaking}).

@menu
* \ensuremath:: Ensure that math mode is active.
@end menu

@node \ensuremath
@section @code{\ensuremath}

Synopsis:

@example
\ensuremath@{@var{formula}@}
@end example

Ensure that @var{formula} is typeset in math mode.

For instance, you can redefine commands that ordinarily can be used only
in math mode, so that they can be used both in math and in plain text.

@example
\newcommand@{\dx@}@{\ensuremath@{dx@}@}
In $\int f(x)\, \dx$, the \dx@{@} is an infinitesimal.
@end example

Caution: the @code{\ensuremath} command is useful but not a panacea.

@example
\newcommand@{\alf@}@{\ensuremath@{\alpha@}@}
You get an alpha in text mode: \alf.
But compare the correct spacing in $\alf+\alf$ with that in \alf+\alf.
@end example

@noindent
Best is to typeset math things in a math mode.


@node Page styles
@chapter Page styles

@cindex styles, page
@cindex page styles

The style of a page determines where @LaTeX{} places the components of
that page, such as headers and footers, and the text body.  This
includes pages in the main part of the document but also includes
special pages such as the title page of a book, a page from an index, or
the first page of an article.

@PkgIndex{fancyhdr}
The package @file{fancyhdr} is very helpful for constructing page
styles.  See its documentation on CTAN.

@menu
* \maketitle::          Generate a title page.
* \pagenumbering::      Set the style used for page numbers.
* \pagestyle::		Change the headings/footings style.
* \thispagestyle::      Change the headings/footings style for this page.
@end menu


@node \maketitle
@section @code{\maketitle}

@cindex titles, making
@findex \maketitle

Synopsis:

@example
\maketitle
@end example

Generate a title.  In the standard classes the title appears on a
separate page, except in the @code{article} class where it is at the top
of the first page.  (@xref{Document class options} for information about
the @code{titlepage} document class option.)

This example shows @code{\maketitle} appearing in its usual place,
immediately after @code{\begin@{document@}}.

@example
\documentclass@{article@}
\title@{Constructing a Nuclear Reactor Using Only Coconuts@}
\author@{Jonas Grumby\thanks@{%
    With the support of a Ginger Grant from the Roy Hinkley Society.@} \\
  Skipper, \textit@{Minnow@}
  \and
  Willy Gilligan\thanks@{%
    Thanks to the Mary Ann Summers foundation
    and to Thurston and Lovey Howell.@}           \\
  Mate, \textit@{Minnow@}
  @}
\date@{1964-Sep-26@}
\begin@{document@}
\maketitle
Just sit right back and you'll hear a tale, a tale of a fateful trip.
That started from this tropic port, aboard this tiny ship. The mate was
a mighty sailin' man, the Skipper brave and sure. Five passengers set
sail that day for a three hour tour. A three hour tour.
  ...
@end example

You tell @LaTeX{} the information used to produce the title by making
the following declarations.  These must come before the
@code{\maketitle}, either in the preamble or in the document body.

@ftable @code
@item \author@{@var{name1} \and @var{name2} \and ...@}
@cindex author, for titlepage
@findex \\ @r{for @code{\author}}
@findex \and @r{for @code{\author}}
Required.  Declare the document author or authors.  The argument is a
list of authors separated by @code{\and} commands.  To separate lines
within a single author's entry, for instance to give the author's
institution or address, use a double backslash, @code{\\}.  If you omit
the @code{\author} declaration then you get @samp{LaTeX Warning: No
\author given}.

@item \date@{@var{text}@}
@cindex date, for titlepage
Optional.  Declare @var{text} to be the document's date.  The @var{text}
doesn't need to be in a date format; it can be any text at all.  If you
omit @code{\date} then @LaTeX{} uses the current date (@pxref{\today}).
To have no date, instead use @code{\date@{@}}.

@item \thanks@{@var{text}@}
@cindex thanks, for titlepage
@cindex credit footnote
Optional.  Produce a footnote.  You can use it in the author information
for acknowledgements as illustrated above, but you can also use it in
the title, or any place a footnote makes sense.  It can be any text at
all so you can use it for any purpose, such as to print an email
address.

@item \title@{@var{text}@}
@cindex title, for titlepage
@findex \\ @r{for @code{\title}}
Required.  Declare @var{text} to be the title of the document.  Get line
breaks inside @var{text} with a double backslash, @code{\\}.  If you
omit the @code{\title} declaration then you get @samp{LaTeX Error: No
\title given}.

@end ftable

To make your own title page, see@tie{}@ref{titlepage}. You can either
create this as a one-off or you can include it as part of a renewed
@code{\maketitle} command.  (Many publishers will provide a class to use
in place of @code{article} that formats the title according to their
house requirements.)


@node \pagenumbering
@section @code{\pagenumbering}

@findex \pagenumbering
@cindex page numbering style

Synopsis:

@example
\pagenumbering@{@var{number-style}@}
@end example

Specifies the style of page numbers, and resets the page number.  The
numbering style is reflected on the page, and also in the table of
contents and other page references.  This declaration has global scope
so its effect is not delimited by braces or environments.

In this example, before the Main section the pages are numbered
@samp{a}, etc.  Starting on the page containing that section, the pages
are numbered @samp{1}, etc.

@example
\begin@{document@}\pagenumbering@{alph@}
  ...
\section@{Main@}\pagenumbering@{arabic@}
  ...
@end example

The argument @var{number-style} is one of the following (see
also@tie{}@ref{\alph \Alph \arabic \roman \Roman \fnsymbol}).

@table @code
@item arabic
Arabic numerals: 1, 2, @dots{} 

@item roman
lowercase Roman numerals: i, ii, @dots{}

@item Roman
uppercase Roman numerals: I, II, @dots{}

@item alph
lowercase letters: a, b, @dots{} If you have more than 26 pages then you
get @samp{LaTeX Error: Counter too large}.

@item Alph
uppercase letters: A, B, @dots{} If you have more than 26 pages then you
get @samp{LaTeX Error: Counter too large}.

@item gobble
@PkgIndex{hyperref} @LaTeX{} does not output a page number, although it
does get reset.  References to that page also are blank.  (This does not
work with the popular package @file{hyperref} so to have the page number
not appear you may want to instead use @code{\pagestyle@{empty@}} or
@code{\thispagestyle@{empty@}}.)

@end table

Traditionally, if a document has front matter---preface, table of
contents, etc.---then it is numbered with lowercase Roman numerals. The
main matter of a document uses arabic.  @xref{\frontmatter & \mainmatter
& \backmatter}.

If you want to address where the page number appears on the page,
see@tie{}@ref{\pagestyle}.  If you want to change the value of page
number then you will manipulate the @code{page} counter
(@pxref{Counters}).


@node \pagestyle
@section @code{\pagestyle}

@findex \pagestyle
@cindex header style
@cindex footer style
@cindex running header and footer style

Synopsis:

@example
\pagestyle@{@var{style}@}
@end example

Declaration that specifies how the page headers and footers are typeset,
from the current page onwards.

@PkgIndex{fancyhdr}
A discussion with an example is below.  Note first that the package
@file{fancyhdr} is now the standard way to manipulate headers and
footers.  New documents that need to do anything other than one of the
standard options below should use this package.  See its documentation
on CTAN.

Values for @var{style}:

@table @code
@item plain
The header is empty.  The footer contains only a page number, centered.

@item empty
The header and footer is empty.

@item headings
Put running headers and footers on each page.  The document style
specifies what goes in there; see the discussion below.

@item myheadings
Custom headers, specified via the @code{\markboth} or the
@code{\markright} commands.

@end table

Some discussion of the motivation for @LaTeX{}'s mechanism will help you
work with the options @code{headings} or @code{myheadings}.  The
document source below produces an article, two-sided, with the pagestyle
@code{headings}.  On this document's left hand pages, @LaTeX{} wants (in
addition to the page number) the title of the current section.  On its
right hand pages @LaTeX{} wants the title of the current subsection.
When it makes up a page, @LaTeX{} gets this information from the
commands @code{\leftmark} and @code{\rightmark}.  So it is up to
@code{\section} and @code{\subsection} to store that information there.

@example
\documentclass[twoside]@{article@}
\pagestyle@{headings@}
\begin@{document@}
  ... \section@{Section 1@} ... \subsection@{Subsection 1.1@} ...
\section@{Section 2@}
  ...
\subsection@{Subsection 2.1@}
  ...
\subsection@{Subsection 2.2@}
  ...
@end example

@noindent
Suppose that the second section falls on a left page.  Although when the
page starts it is in the first section, @LaTeX{} will put
@samp{Section@tie{}2} in the left page header.  As to the right header,
if no subsection starts before the end of the right page then @LaTeX{}
blanks the right hand header.  If a subsection does appear before the
right page finishes then there are two cases.  If at least one
subsection starts on the right hand page then @LaTeX{} will put in the
right header the title of the first subsection starting on that right
page.  If at least one of 2.1, 2.2, @dots{}, starts on the left page but
none starts on the right then @LaTeX{} puts in the right hand header the
title of the last subsection to start, that is, the one in effect during
the right hand page.

To accomplish this, in a two-sided article, @LaTeX{} has @code{\section}
issue a command @code{\markboth}, setting @code{\leftmark}
to @samp{Section@tie{}2} and setting @code{\rightmark} to blank.
And, @LaTeX{} has @code{\subsection} issue a command @code{\markright},
setting @code{\rightmark} to @samp{Subsection@tie{}2.1}, etc.

Here are the descriptions of @code{\markboth} and @code{\markright}:

@ftable @code
@item \markboth@{@var{left-head}@}@{@var{right-head}@}
Sets both the right hand and left hand heading information for either a
page style of @code{headings} or @code{myheadings}.  A left hand page
heading @var{left-head} is generated by the last @code{\markboth}
command before the end of the page.  A right hand page heading
@var{right-head} is generated by the first @code{\markboth} or
@code{\markright} that comes on the page if there is one, otherwise by
the last one that came before that page.

@item \markright@{@var{right}@}
Sets the right hand page heading, leaving the left unchanged.

@end ftable


@node \thispagestyle
@section @code{\thispagestyle}

@findex \thispagestyle
@cindex page style, this page

Synopsis:

@example
\thispagestyle@{@var{style}@}
@end example

Works in the same way as the @code{\pagestyle} (@pxref{\pagestyle}),
except that it changes to @var{style} for the current page only.  This
declaration has global scope, so its effect is not delimited by braces
or environments.

Often the first page of a chapter or section has a different style.  For
example, this @LaTeX{} book document has the first page of the first
chapter in @code{plain} style, as is the default (@pxref{Page
styles}).

@example
\documentclass@{book@}
\pagestyle@{headings@}
\begin@{document@}
\chapter@{First chapter@}
  ...
\chapter@{Second chapter@}\thispagestyle@{empty@}
  ...
@end example

@noindent
The @code{plain} style has a page number on it, centered in the footer.
To make the page entirely empty, the command
@code{\thispagestyle@{empty@}} immediately follows the second
@code{\chapter}.


@node Spaces
@chapter Spaces

@cindex spaces
@cindex white space

@LaTeX{} has many ways to produce white (or filled) space.  Some of
these are best suited to mathematical text; see@tie{}@ref{Spacing in
math mode}.  Some spacing commands are suitable for both regular text
and mathematical text; versions of some of these commands are in this
chapter.

@menu
Horizontal space 
* \enspace & \quad & \qquad::  Traditional horizontal spaces.  
* \hspace::               Any horizontal space.  
* \hfill::                Stretchable horizontal space.  
* \hss::                  Infinitely stretchable/shrinkable horizontal space.
* \spacefactor::          Stretchability of following space
* \(SPACE)::              Backslash-space; and explicit space.
* ~::                     Tie, an unbreakable space.
* \thinspace & \negthinspace::  One-sixth of an em, and negative one-sixth.  
* \/::                    Italic correction.
* \hrulefill & \dotfill:: Stretchable horizontal rule or dots.

Vertical space
* \bigskip & \medskip & \smallskip::  Inter-paragraph vertical spaces.
* \bigbreak & \medbreak & \smallbreak::  Inter-paragraph space and page breaks.
* \strut::                            Ensure height of a line.
* \vspace::                           Vertical space.
* \vfill::                            Stretchable vertical space.
* \addvspace::                        Add arbitrary vertical space if needed.
@end menu


@node \enspace & \quad & \qquad
@section @code{\enspace} & @code{\quad} & @code{\qquad}

@findex \enspace
@findex \quad
@findex \qquad

Synopsis, one of:

@example
\enspace
\quad
\qquad
@end example

Insert a horizontal space of 1/2@dmn{em}, 1@dmn{em}, or 2@dmn{em}. The
em is a length defined by a font designer, often thought of as being the
width of a capital@tie{}M.  One advantage of describing space in ems is
that it can be more portable across documents than an absolute
measurement such as points (@pxref{Lengths/em}).

This puts a suitable gap between two graphics.

@example
\begin@{center@}
  \includegraphics@{womensmile.png@}%
  \qquad\includegraphics@{mensmile.png@}
\end@{center@}
@end example

@noindent
@xref{Spacing in math mode} for @code{\quad} and @code{\qquad}.  These
are lengths from centuries of typesetting and so may be a better choice
in many circumstances than arbitrary lengths, such as you get with
@code{\hspace}.


@node \hspace
@section @code{\hspace}

@findex \hspace

Synopsis, one of:

@example
\hspace@{@var{length}@}
\hspace*@{@var{length}@}
@end example

Insert the horizontal space @var{length}.  The @var{length} can be
positive, negative, or zero; adding negative space is like backspacing.
It is a rubber length, that is, it may contain a @code{plus} or
@code{minus} component, or both (@pxref{Lengths}).  Because the space is
stretchable and shrinkable, it is sometimes called @dfn{glue}.

This makes a line with @samp{Name:} an inch from the right margin.

@example
\noindent\makebox[\linewidth][r]@{Name:\hspace@{1in@}@}
@end example

The @code{*}-version inserts horizontal space that non-discardable.
More precisely, when @TeX{} breaks a paragraph into lines any white
space---glues and kerns---that come at a line break are discarded.  The
@code{*}-version avoids that (technically, it adds a non-discardable
invisible item in front of the space).

In this example

@example
\parbox@{0.8\linewidth@}@{%
  Fill in each blank: Four \hspace*@{1in@} and seven years ago our
  fathers brought forth on this continent, a new \hspace*@{1in@},
  conceived in \hspace*@{1in@}, and dedicated to the proposition
  that all men are created \hspace*@{1in@}.@}
@end example

@noindent
the 1@tie{}inch blank following @samp{conceived in} falls at the start
of a line.  If you erase the @code{*} then @LaTeX{} discards the blank.

Here, the @code{\hspace} separates the three graphics.

@example
\begin@{center@}
  \includegraphics@{lion.png@}%   comment keeps out extra space
  \hspace@{1cm minus 0.25cm@}\includegraphics@{tiger.png@}%
  \hspace@{1cm minus 0.25cm@}\includegraphics@{bear.png@}
\end@{center@}
@end example

@noindent
Because the argument to each @code{\hspace} has @code{minus 0.25cm},
each can shrink a little if the three figures are too wide.  But each
space won't shrink more than 0.25@dmn{cm} (@pxref{Lengths}).


@node \hfill
@section @code{\hfill}

@findex \hfill

@cindex stretch, infinite horizontal
@cindex infinite horizontal stretch

Synopsis:

@example
\hfill
@end example

Produce a rubber length which has no natural space but that can stretch
horizontally as far as needed (@pxref{Lengths}).

This creates a one-line paragraph with @samp{Name:} on the left side
of the page and @samp{Quiz One} on the right.

@example
\noindent Name:\hfill Quiz One
@end example

@findex \fill
The @code{\hfill} command is equivalent to @code{\hspace@{\fill@}} and
so the space can be discarded at line breaks.  To avoid that instead use
@code{\hspace*@{\fill@}} (@pxref{\hspace}).

Here the graphs are evenly spaced in the middle of the figure.

@example
\newcommand*@{\vcenteredhbox@}[1]@{\begin@{tabular@}@{@@@{@}c@@@{@}@}#1\end@{tabular@}@}
  ...
\begin@{figure@}
  \hspace*@{\fill@}%
  \vcenteredhbox@{\includegraphics@{graph0.png@}@}%
    \hfill\vcenteredhbox@{\includegraphics@{graph1.png@}@}%
  \hspace*@{\fill@}%
  \caption@{Comparison of two graphs@} \label@{fig:twographs@}
\end@{figure@}
@end example

@noindent
Note the @code{\hspace*}'s where the space could otherwise be dropped.


@node \hss
@section @code{\hss}

@findex \hss
@cindex horizontal space
@cindex horizontal space, stretchable
@cindex space, inserting horizontal

Synopsis:

@example
\hss
@end example

Produce a horizontal space that is infinitely shrinkable as well as
infinitely stretchable (this command is a @TeX{} primitive).  @LaTeX{}
authors should reach first for the @code{\makebox} command to get the
effects of @code{\hss} (@pxref{\mbox & \makebox}).

Here, the first line's @code{\hss} makes the Z stick out to the right,
overwriting the Y.  In the second line the Z sticks out to the left,
overwriting the X.

@example
X\hbox to 0pt@{Z\hss@}Y
X\hbox to 0pt@{\hss Z@}Y
@end example

@noindent
Without the @code{\hss} you get something like @samp{Overfull \hbox
(6.11111pt too wide) detected at line 20}.


@node \spacefactor
@section @code{\spacefactor}

Synopsis:

@example
\spacefactor=@var{integer}
@end example

@findex \spacefactor
Influence @LaTeX{}'s glue stretch and shrink behavior.  Most user-level
documents do not use this command.

While @LaTeX{} is laying out the material, it may stretch or shrink the
gaps between words.  (This space is not a character; it is called the
@dfn{interword glue}; @pxref{\hspace}).  The @code{\spacefactor} command
(from Plain@tie{}@TeX{}) allows you to, for instance, have the space
after a period stretch more than the space after a word-ending letter.

After @LaTeX{} places each character, or rule or other box, it sets a
parameter called the @dfn{space factor}.  If the next thing in the input
is a space then this parameter affects how much stretching or shrinking
can happen.  A space factor that is larger than the normal value means
that the glue can stretch more and shrink less.  Normally, the space
factor is 1000. This value is in effect following most characters, and
any non-character box or math formula.  But it is 3000 after a period,
exclamation mark, or question mark, it is 2000 after a colon, 1500 after
a semicolon, 1250 after a comma, and 0 after a right parenthesis or
bracket, or closing double quote or single quote.  Finally, it is 999
after a capital letter.

If the space factor@tie{}@var{f} is 1000 then the glue gap will be the
font's normal space value (for Computer Modern Roman 10 point this is
3.3333@tie{}points).  Otherwise, if the space factor @var{f} is greater
than 2000 then @TeX{} adds the font's extra space value (for Computer
Modern Roman 10 point this is 1.11111@tie{}points), and then the font's
normal stretch value is multiplied by @math{f /1000} and the normal
shrink value is multiplied by @math{1000/f} (for Computer Modern Roman
10 point these are 1.66666 and 1.11111@tie{}points).

For example, consider the period ending @code{A man's best friend is his
dog.}  After it, @TeX{} puts in a fixed extra space, and also allows the
glue to stretch 3 times as much and shrink 1/3 as much, as the glue
after @code{friend}, which does not end in a period.

The rules for space factors are even more complex because they play
additional roles.  In practice, there are two consequences.  First, if a
period or other punctuation is followed by a right parenthesis or
bracket, or right single or double quote then the spacing effect of that
period carries through those characters (that is, the following glue
will have increased stretch and shrink).  Second, if
punctuation comes after a capital letter then its effect is not in place
so you get an ordinary space.  This second case also affects abbreviations
that do not end in a capital letter (@pxref{\@@}).

You can only use @code{\spacefactor} in paragraph mode or LR mode
(@pxref{Modes}).  You can see the current value with
@code{\the\spacefactor} or @code{\showthe\spacefactor}.

(Comment, not really related to @code{\spacefactor}: if you get errors
like @samp{You can't use `\spacefactor' in vertical mode}, or @samp{You
can't use `\spacefactor' in math mode.}, or @samp{Improper \spacefactor}
then you have probably tried to redefine an internal command.
@xref{\makeatletter & \makeatother}.)


@menu
* \@@::              Distinguish sentence-ending periods from abbreviations.  
* \frenchspacing::   Equal interword and inter-sentence space.
* \normalsfcodes::   Restore space factor settings to the default.
@end menu


@node \@@ 
@subsection @code{\@@}  

@findex \@@
@findex at-sign
@cindex period, sentence-ending
@cindex period, abbreviation-ending
@cindex period, spacing after
@anchor{\AT}@c old name

Synopsis:

@example
@var{capital-letter}\@@.    
@end example

Treat a period as sentence-ending, where @LaTeX{} would otherwise think
it is part of an abbreviation.  @LaTeX{} thinks that a period ends an
abbreviation if the period comes after a capital letter, and otherwise
thinks the period ends the sentence.  By default, in justifying a line
@LaTeX{} adjusts the space after a sentence-ending period (or a question
mark, exclamation point, comma, or colon) more than it adjusts the space
between words (@pxref{\spacefactor}).

This example shows the two cases to remember.

@example
The songs \textit@{Red Guitar@}, etc.\ are by Loudon Wainwright~III\@@.
@end example

@noindent
The second period ends the sentence, despite that it is preceded by a
capital.  We tell @LaTeX{} that it ends the sentence by putting
@code{\@@} before it.  The first period ends the abbreviation
@samp{etc.} but not the sentence.  The backslash-space, @code{\ },
produces a mid-sentence space.

So: if you have a capital letter followed by a period that ends the
sentence, then put @code{\@@} before the period.  This holds even if
there is an intervening right parenthesis or bracket, or right single or
double quote, because the spacing effect of that period carries through
those characters.  For example, this

@example
Use the \textit@{Instructional Practices Guide@},
(a book by the MAA)\@@.
@end example

@noindent
will have correct inter-sentence spacing after the period.

The @code{\@@} command is only for a text mode. If you use it outside of
a text mode then you get @samp{You can't use `\spacefactor' in vertical
mode} (@pxref{Modes}).

Comment: the converse case is a period ending an abbreviation whose last
letter is not a capital letter, and that abbreviation is not the last
word in the sentence.  For that case follow the period with a
backslash-space, (@code{\ }), or a tie, (@code{~}), or @code{\@@}.
Examples are @code{Nat.\ Acad.\ Science}, and @code{Mr.~Bean}, and
@code{(manure, etc.\@@) for sale} (note in the last one that the
@code{\@@} comes before the closing parenthesis).


@node \frenchspacing
@subsection @code{\frenchspacing}

@findex \frenchspacing
@findex \nonfrenchspacing
@cindex spacing, inter-sentence

Synopsis, one of:

@example
\frenchspacing
\nonfrenchspacing
@end example

The first declaration causes @LaTeX{} to treat spacing between sentences
in the same way as spacing between words in the middle of a sentence.
The second causes spacing between sentences to stretch or shrink more
(@pxref{\spacefactor}); this is the default.

Some typographic traditions, including English, prefer to adjust the
space between sentences (or spaces following a question mark,
exclamation point, comma, or colon) more than the space between words
that are in the middle of a sentence.  Declaring @code{\frenchspacing}
(the command is from Plain @TeX{}) switches to the tradition that all
spaces are treated equally.


@node \normalsfcodes
@subsection @code{\normalsfcodes}

@findex \normalsfcodes
@cindex spacing, inter-sentence

Synopsis:

@example
\normalsfcodes
@end example

Reset the @LaTeX{} space factor values to the default
(@pxref{\spacefactor}).


@node \(SPACE) 
@section Backslash-space, @code{\ }

@cindex \NEWLINE
@cindex \SPACE
@cindex \TAB

This section refers to the command consisting of two characters, a
backslash followed by a space. Synopsis:

@example
\    
@end example

Produce a space. By default it produces white space of length
3.33333@dmn{pt} plus 1.66666@dmn{pt} minus 1.11111@dmn{pt}.

When you type one or more blanks between words, @LaTeX{} produces white
space.  But that is different than an explicit space.  This illustrates.

@example
\begin@{tabular@}@{l@}
One blank: makes some space \\
Three blanks:   in a row \\
Three spaces:\ \ \ in a row \\
\end@{tabular@}
@end example

@noindent
On the first line @LaTeX{} puts some space after the colon.  On the
second line @LaTeX{} collapses the three blanks to output one
whitespace, so you end with the same space after the colon as in the
first line.  @LaTeX{} would similarly collapse a blank followed by a
tab, or a blank and a newline and a blank.  However, the bottom line
asks for three spaces so the white area is wider.  That is, the
backslash-space command creates a fixed amount of horizontal space.
(Note that you can define a horizontal space of any width at all with
@code{\hspace}; see@tie{}@ref{\hspace}.)

The backslash-space command has two main uses.  It is often used after
control sequences to keep them from gobbling the space that follows, as
in @code{\TeX\ is nice}.  (But using curly parentheses, as in
@code{\TeX@{@} is best}, has the advantage of still working if the next
character is a period.)  The other common use is that it marks a period
as ending an abbreviation instead of ending a sentence, as in @code{So
says Prof.\ Smith} (@pxref{\@@}).

Under normal circumstances, @code{\}@key{tab} and @code{\}@key{newline}
are equivalent to backslash-space, @code{\ }.

@c @PkgIndex{xspace}
@c Some individual commands, notably those defined with the @code{xspace},
@c package do not follow the standard behavior.


@node ~
@section @code{~}

@findex ~
@cindex tie
@cindex space, hard
@cindex space, unbreakable
@cindex NBSP

Synopsis:

@example
@var{before}~@var{after}
@end example

The tie character, @code{~}, produces a space between @var{before} and
@var{after} at which the line will not be broken. By default the white
space has length 3.33333@dmn{pt} plus 1.66666@dmn{pt} minus
1.11111@dmn{pt} (@pxref{Lengths}).

Here @LaTeX{} will not break the line between the final two words.

@example
Thanks to Prof.~Lerman.
@end example

@noindent
In addition, despite the period, @LaTeX{} does not use the
end-of-sentence spacing (@pxref{\@@}).

Ties prevent the end of line separation of things where that could cause
confusion. But they also reduce @LaTeX{}'s options when it breaks lines
into paragraphs, so you can use too many. They are also matters of
taste, sometimes alarmingly dogmatic taste, among readers. Nevertheless,
here are some usage models, many of them from the @TeX{}book.

@itemize @bullet
@item
Between an enumerator and its item, such as in references:
@code{Chapter~12}, or @code{Theorem~\ref@{th:Wilsons@}}, or
@code{Figure~\ref@{fig:KGraph@}}. When cases are enumerated inline:
@code{(b)~Show that $f(x)$ is (1)~continuous, and (2)~bounded}.

@PkgIndex{siunitx}
@item
Between a number and its unit: @code{$745.7.8$~watts} (the
@file{siunitx} package has a special facility for this) or
@code{144~eggs}. This includes between a month and a date:
@code{October~12} or @code{12~Oct}. In general, in any expressions where
numbers and abbreviations or symbols are separated by a space:
@code{AD~565}, or @code{2:50~pm}, or @code{Boeing~747}, or
@code{268~Plains Road}, or @code{\$$1.4$~billion}.

@item
When mathematical phrases are rendered in words: @code{equals~$n$}, or
@code{less than~$\epsilon$}, or @code{given~$X$}, or @code{modulo~$p^e$
for all large~$n$} (but compare @code{is~$15$} with @code{is $15$~times
the height}). Between mathematical symbols in apposition with nouns:
@code{dimension~$d$} or @code{function~$f(x)$} (but compare @code{with
length $l$~or more}). When a symbol is a tightly bound object of a
preposition: @code{of~$x$}, or @code{from $0$ to~$1$}, or @code{in
common with~$m$}.

@item
Between symbols in series: @code{$1$,~$2$, or~$3$} or @code{$1$,~$2$,
\ldots,~$n$}.

@item
Between a person's forenames and between multiple surnames:
@code{Donald~E. Knuth}, or @code{Luis~I. Trabb~Pardo}, or
@code{Charles~XII} (but you must give TeX places to break the line so
you may do @code{Charles Louis Xavier~Joseph de~la Vall\'ee~Poussin}).

@item
Before a dash: @code{pages 12~--14} or @code{it is~--- it must be
said~--- plausible}.

@end itemize


@node \thinspace & \negthinspace
@section @code{\thinspace} & @code{\negthinspace}

@findex \thinspace
@findex \negthinspace
@cindex thin space
@cindex space, thin
@cindex thin space, negative
@cindex space, negative thin

Synopsis, one of:

@example
\thinspace
\negthinspace
@end example

Produce an unbreakable and unstretchable space of 1/6@dmn{em} and
-1/6@dmn{em}.  These are the text mode equivalents of @code{\,} and
@code{\!} (@pxref{Spacing in math mode/\thinspace}).  You can use
@code{\,} as a synonym for @code{\thinspace} in text mode.

The @code{\negthinspace} command is used in text mode mostly for
fiddling with spaces.  One common use of @code{\thinspace} is as the
space between nested quotes.

@example
Killick replied, ``I heard the Captain say, `Ahoy there.'\thinspace''
@end example

@noindent
Another use is that some style guides call for a @code{\thinspace}
between an ellipsis and a sentence ending period (other style guides,
though, think the three dots are quite enough already).  Still another
use is between initials, as in @code{D.\thinspace E.\ Knuth}.


@node \/
@section @code{\/}

@findex \/
@cindex italic correction

Synopsis:

@example
@var{before-character}\/@var{after-character}
@end example

Insert an @dfn{italic correction}, a small space defined by the font
designer for each character, to avoid the character colliding with
whatever follows. When you use @code{\/}, @LaTeX{} takes the correction
from the font metric file, scales it by any scaling that has been
applied to the font, and then inserts that much horizontal space.

Here, were it not for the @code{\/}, the @var{before-character}
italic@tie{}f would hit the @var{after-character} roman@tie{}H

@example
\newcommand@{\companylogo@}@{@{\it f@}\/H@}
@end example

@noindent 
because the italic letter leans far to the right.

If @var{after-character} is a period or comma then don't insert an
italic correction since those punctuation symbols have a very small
height.  However, with semicolons or colons as well as with normal
letters, the italic correction can help.

When you use commands such as @code{\textit} or @code{\itshape} to
change fonts, @LaTeX{} will automatically insert any needed italic
correction (@pxref{Font styles}).

Roman characters can also have an italic correction.  An example is in
the name @code{pdf\/\TeX}.

There is no concept of italic correction in math mode; spacing is done
in a different way.


@node \hrulefill & \dotfill
@section @code{\hrulefill} & @code{\dotfill}

@findex \hrulefill
@findex \dotfill

Synopsis, one of:

@example
\hrulefill
\dotfill
@end example

Produce an infinite horizontal rubber length (@pxref{Lengths}) that
@LaTeX{} fills with a rule (that is, a line) or with dots, instead of
white space.

This outputs a line 2 inches long.

@example
Name:~\makebox[2in]@{\hrulefill@}
@end example

@noindent
This example, when placed between blank lines, creates a paragraph that
is left and right justified and where the middle is filled with evenly
spaced dots.

@example
\noindent John Aubrey, RN \dotfill@{@} Melbury Lodge
@end example

To make the rule or dots go to the line's end use @code{\null} at the
start or end.  

To change the rule's thickness, copy the definition and adjust it, as
here

@example
\renewcommand@{\hrulefill@}@{%
  \leavevmode\leaders\hrule height 1pt\hfill\kern\z@@@}
@end example

@noindent
which changes the default thickness of 0.4@dmn{pt} to 1@dmn{pt}.
Similarly, adjust the dot spacing as with

@example
\renewcommand@{\dotfill@}@{%
  \leavevmode\cleaders\hb@@xt@@1.00em@{\hss .\hss @}\hfill\kern\z@@@}
@end example

@noindent
which changes the default length of 0.33@dmn{em} to 1.00@dmn{em}.

This example produces a line for a signature.

@example
\begin@{minipage@}@{4cm@}
  \centering
  \hrulefill\\
  Signed
\end@{minipage@}
@end example

@noindent
The line is 4@dmn{cm} long.


@node \bigskip & \medskip & \smallskip
@section @code{\bigskip} & @code{\medskip} & @code{\smallskip}

Synopsis, one of:

@example
\bigskip
\medskip
\smallskip
@end example

Produce an amount of vertical space, large or medium-sized or
small. These commands are fragile (@pxref{\protect}).

Here the skip suggests the passage of time (from @i{The Golden Ocean} by
O'Brian).

@example
Mr Saumarez would have something rude to say to him, no doubt: he
was at home again, and it was delightful.

\bigskip
``A hundred and fifty-seven miles and one third, in twenty-four hours,''
said Peter.
@end example

Each command is associated with a length defined in the document class
file.

@ftable @code
@anchor{bigskip}
@item \bigskip
@findex \bigskipamount
The same as @code{\vspace@{\bigskipamount@}}, ordinarily about one line
space, with stretch and shrink.  The default for the @code{book} and
@code{article} classes is @code{12pt plus 4pt minus 4pt}.

@anchor{medskip}
@item \medskip
@findex \medskipamount
The same as @code{\vspace@{\medskipamount@}}, ordinarily about half of a
line space, with stretch and shrink.  The default for the @code{book}
and @code{article} classes is @code{6pt plus 2pt minus 2pt}.

@anchor{smallskip}
@item \smallskip
@findex \smallskipamount
The same as @code{\vspace@{\smallskipamount@}}, ordinarily about a
quarter of a line space, with stretch and shrink.  The default for the
@code{book} and @code{article} classes is @code{3pt plus 1pt minus 1pt}.

@end ftable

Because each command is a @code{\vspace}, if you use on in mid-paragraph
then it will insert its vertical space between the line in which you use
it and the next line, not necessarily at the place that you use it.  So
these are best between paragraphs.

The commands @code{\bigbreak}, @code{\medbreak}, and @code{\smallbreak}
are similar but also suggest to @LaTeX{} that this is a good place to
put a page break (@pxref{\bigbreak & \medbreak & \smallbreak}.


@node \bigbreak & \medbreak & \smallbreak
@section @code{\bigbreak} & @code{\medbreak} & @code{\smallbreak}

Synopsis, one of:

@example
\bigbreak
\medbreak
\smallbreak
@end example

Produce a vertical space that is big or medium-sized or small, and
suggest to @LaTeX{} that this is a good place to break the page.  (The
associated penalties are -200, -100, and -50.)

@xref{\bigskip & \medskip & \smallskip}, for more.  These commands
produce the same vertical space but differ in that they also remove a
preceding vertical space if it is less than what they would insert (as
with @code{\addvspace}).  In addition, they terminate a paragraph where
they are used: this example

@example
abc\bigbreak def ghi

jkl mno pqr
@end example

@noindent
will output three paragraphs, the first ending in @samp{abc} and the
second starting, after an extra vertical space and a paragraph indent,
with @samp{def}.


@node \strut
@section @code{\strut}

@findex \strut
@cindex strut

Synopsis:

@example
\strut
@end example

Ensure that the current line has height at least @code{0.7\baselineskip}
and depth at least @code{0.3\baselineskip}.  Essentially, @LaTeX{}
inserts into the line a rectangle having zero width,
@code{\rule[-0.3\baselineskip]@{0pt@}@{\baselineskip@}} (@pxref{\rule}).
The @code{\baselineskip} changes with the current font and fontsize.

In this example the @code{\strut} keeps the box inside the frame from
having zero height.

@example
\setlength@{\fboxsep@}@{0pt@}\framebox[2in]@{\strut@}
@end example

This example has four lists.  In the first there is a much bigger gap
between items 2 and@tie{}3 than there is between items 1 and@tie{}2.
The second list fixes that with a @code{\strut} at the end of its first
item's second line.

@example
\setlength@{\fboxsep@}@{0pt@}
\noindent\begin@{minipage@}[t]@{0.2\linewidth@}
\begin@{enumerate@}
  \item \parbox[t]@{15pt@}@{test \\ test@}
  \item test
  \item test
\end@{enumerate@}
\end@{minipage@}%
\begin@{minipage@}[t]@{0.2\linewidth@}
\begin@{enumerate@}
  \item \parbox[t]@{15pt@}@{test \\ test\strut@}
  \item test
  \item test
\end@{enumerate@}
\end@{minipage@}%
\begin@{minipage@}[t]@{0.2\linewidth@}
\begin@{enumerate@}
  \item \fbox@{\parbox[t]@{15pt@}@{test \\ test@}@}
  \item \fbox@{test@}
  \item \fbox@{test@}
\end@{enumerate@}
\end@{minipage@}%
\begin@{minipage@}[t]@{0.2\linewidth@}
\begin@{enumerate@}
  \item \fbox@{\parbox[t]@{15pt@}@{test \\ test\strut@}@}
  \item \fbox@{test@}
  \item \fbox@{test@}
\end@{enumerate@}
\end@{minipage@}%
@end example

@noindent
The final two lists use @code{\fbox} to show what's happening.  The
third list's @code{\parbox} goes only to the bottom of its second
@samp{test}, which happens not have any characters that descend below
the baseline.  The fourth list adds the strut that gives the needed
extra below-baseline space.

@PkgIndex{TikZ} @PkgIndex{Asymptote}
The @code{\strut} command is often useful in graphics, such as in
@file{TikZ} or @file{Asymptote}.  For instance, you may have a command
such as @code{\graphnode@{@var{node-name}@}} that fits a circle around
@var{node-name}.  However, unless you are careful the @var{node-name}'s
@samp{x} and @samp{y} will produce different-diameter circles because
the characters are different sizes.  A careful @code{\graphnode} might
insert a @code{\strut}, then @var{node-name}, and then draw the circle.

The general approach of using a zero width @code{\rule} is useful in
many circumstances.  In this table, the zero-width rule keeps the top of
the first integral from hitting the @code{\hline}.  Similarly, the
second rule keeps the second integral from hitting the first.

@example
\begin@{tabular@}@{rl@}
  \textsc@{Integral@}   &\textsc@{Value@}           \\
  \hline
  $\int_0^x t\, dt$   &$x^2/2$  \rule@{0em@}@{2.5ex@} \\  
  $\int_0^x t^2\, dt$ &$x^3/3$  \rule@{0em@}@{2.5ex@}
\end@{tabular@}
@end example

@noindent
(Although the line-ending double backslash command has an available
optional argument to put in more vertical room, that won't work here.
Changing the first double backslash to something like @code{\\[2.5ex]}
will put the room between the header line and the @code{\hline}, and the
integral would still hit the line.)


@node \vspace
@section @code{\vspace}

@findex \vspace
@cindex vertical space
@cindex space, vertical

Synopsis, one of:

@example
\vspace@{@var{length}@}
\vspace*@{@var{length}@}
@end example

Add the vertical space @var{length}.  The @var{length} can be positive,
negative, or zero.  It is a rubber length---it may contain a @code{plus}
or @code{minus} component (@pxref{Lengths}).

This puts space between the two paragraphs.

@example
And I slept.

\vspace@{1ex plus 0.5ex@}
The new day dawned cold.
@end example

@noindent
(@xref{\bigskip & \medskip & \smallskip} for common inter-paragraph
spaces.)

The @code{*}-version inserts vertical space that non-discardable.  More
precisely, @LaTeX{} discards vertical space at a page break and the
@code{*}-version causes the space to stay.  This example leaves space
between the two questions.

@example
Question: Find the integral of \( 5x^4+5 \).

\vspace*@{2cm plus 0.5cm@}
Question: Find the derivative of \( x^5+5x+9 \).
@end example

@noindent
That space will be present even if the page break happens to fall
between the questions.

If you use @code{\vspace} in the middle of a paragraph (i.e., in
horizontal mode) then the space is inserted after the line containing
the @code{\vspace} command; it does not start a new paragraph at the
@code{\vspace} command.

In this example the two questions will be evenly spaced vertically on
the page, with at least one inch of space below each.

@example
\begin@{document@}
1) Who put the bomp in the bomp bah bomp bah bomp?
\vspace@{1in plus 1fill@}

2) Who put the ram in the rama lama ding dong?
\vspace@{1in plus 1fill@}
\end@{document@}
@end example


@node \vfill
@section @code{\vfill}

@findex \vfill

@cindex stretch, infinite vertical
@cindex infinite vertical stretch

Synopsis:

@example
\vfill
@end example 

End the current paragraph and insert a vertical rubber length that is
infinite, so it can stretch or shrink as far as needed
(@pxref{Lengths}).

It is often used in the same way as @code{\vspace@{\fill@}}, except that
@code{\vfill} ends the current paragraph whereas @code{\vspace@{\fill@}}
adds the infinite vertical space below its line, irrespective of the
paragraph structure.  In both cases that space will disappear at a page
boundary; to circumvent this see the starred option
in@tie{}@ref{\vspace}.

In this example the page is filled, so the top and bottom lines contain
the text @samp{Lost Dog!} and the second @samp{Lost Dog!} is exactly
halfway between them.
 
@example
\begin@{document@}
Lost Dog!
\vfill
Lost Dog!  % perfectly in the middle
\vfill
Lost Dog!
\end@{document@}
@end example


@node \addvspace
@section @code{\addvspace}

@findex \addvspace
@cindex vertical space
@cindex space, inserting vertical

Synopsis:

@example
\addvspace@{@var{vert-length}@}
@end example

Add a vertical space of @var{vert-length}.  However, if there are two or
more @code{\addvspace}'s in a sequence then together they only add the
space needed to make the natural length equal to the maximum of the
@var{vert-length}'s in that sequence. This command is fragile
(@pxref{\protect}).  The @var{vert-length} is a rubber length
(@pxref{Lengths}).

This example illustrates.  The @code{picture} draws a scale.  In a
standard @LaTeX{} article the length @code{\baselineskip} is 12@dmn{pt}.
The two rules here are 22@dmn{pt} apart: the sum of the
@code{\baselineskip} and the 10@dmn{pt} from the first @code{addvspace}.

@example
\documentclass@{article@}
\usepackage@{color@}
\begin@{document@}
\setlength@{\unitlength@}@{2pt@}%
\noindent\begin@{picture@}(0,0)%
  \multiput(0,0)(0,-1)@{25@}@{@{\color@{blue@}\line(1,0)@{1@}@}@}
  \multiput(0,0)(0,-5)@{6@}@{@{\color@{red@}\line(1,0)@{2@}@}@}
\end@{picture@}%
\rule@{0.25\linewidth@}@{0.1pt@}% 
\par\addvspace@{10pt@}% \addvspace@{20pt@}%
\par\noindent\rule@{0.25\linewidth@}@{0.1pt@}%
\end@{document@}
@end example

@noindent
Now uncomment the second @code{\addvspace}.  It does not make the gap
20@dmn{pt} longer; instead the gap is the sum of @code{\baselineskip}
and 20@dmn{pt}.  So @code{\addvspace} in a sense does the opposite of
its name --- it makes sure that multiple vertical spaces do not
accumulate, but instead that only the largest one is used.

@LaTeX{} uses this command to adjust the vertical space above or below
an environment that starts a new paragraph.  For instance, a
@code{theorem} environment begins and ends with @code{\addvspace} so
that two consecutive @code{theorem}'s are separated by one vertical
space, not two.

A error @samp{Something's wrong--perhaps a missing \item} pointing to an
@code{\addvspace} means that you were not in vertical mode when you hit
this command. One way to change that is to precede @code{\addvspace}
with a @code{\par} command (@pxref{\par}), as in the above example.


@node Boxes
@chapter Boxes

@cindex boxes

@c xx Expand on boxes and glue, for xref from elsewhere.
At its core, @LaTeX{} puts things in boxes and then puts the boxes on a
page.  So these commands are central.

There are many packages on CTAN that are useful for manipulating boxes.
One useful adjunct to the commands here is @file{adjustbox}.

@menu
* \mbox & \makebox::    Horizontal boxes.
* \fbox & \framebox::   Put a frame around a box.
* \parbox::             Box with text in paragraph mode.
* \raisebox::           Raise or lower text.
* \sbox & \savebox::    Like @code{\makebox} but save the text for later.
* lrbox::               Environment version of @code{\sbox}.
* \usebox::             Print saved text.
@end menu


@node \mbox & \makebox
@section @code{\mbox} & @code{\makebox}

@findex \mbox
@findex \makebox
@cindex box
@cindex make a box
@cindex hyphenation, preventing

Synopsis, one of:

@example
\mbox@{@var{text}@}
\makebox@{@var{text}@}
\makebox[@var{width}]@{@var{text}@}
\makebox[@var{width}][@var{position}]@{@var{text}@}
@end example

Create a box, a container for material.  The @var{text} is typeset in
LR mode (@pxref{Modes}) so it is not broken into lines.  The
@code{\mbox} command is robust, while @code{\makebox} is fragile
(@pxref{\protect}).

Because @code{text} is not broken into lines, you can use @code{\mbox}
to prevent hyphenation.  In this example, @LaTeX{} will not hyphenate
the table name, @samp{T-4}.

@example
See Table~\mbox@{T-4@}
@end example

The first two command versions, @code{\mbox} and @code{\makebox}, are
roughly equivalent.  They create a box just wide enough to contain the
@var{text}.  (They are like plain @TeX{}'s @code{\hbox}.)

In the third version the optional argument @var{width} specifies the
width of the box.  Note that the space occupied by the text need not
equal the width of the box.  For one thing, @var{text} can be too small;
this creates a full-line box

@example
\makebox[\linewidth]@{Chapter Exam@}
@end example

@noindent
with @samp{Chapter Exam} centered.  But @var{text} can also be too wide
for @var{width}.  See the example below of zero-width boxes.

@anchor{mbox makebox depth}
@anchor{mbox makebox height}
@anchor{mbox makebox width}
@anchor{mbox makebox totalheight}
In the @var{width} argument you can use the following lengths that refer
to the dimension of the box that @LaTeX{} gets on typesetting
@var{text}: @code{\depth}, @code{\height}, @code{\width},
@code{\totalheight} (this is the box's height plus its depth).  For
example, to make a box with the text stretched to double the natural
size you can say this.

@example
\makebox[2\width]@{Get a stretcher@}
@end example

For the fourth command version the optional argument @var{position}
gives position of the text within the box. It may take the following
values:

@table @code
@item c
The @var{text} is centered (default).

@item l
The @var{text} is flush left.

@item r
Flush right.

@item s
Stretch the interword space in @var{text} across the entire @var{width}.
The @var{text} must contain stretchable space for this to work.  For
instance, this could head a press release:
@code{\noindent\makebox[\textwidth][s]@{\large\hfil IMMEDIATE\hfil
RELEASE\hfil@}}
@end table

A common use of @code{\makebox} is to make zero-width text boxes.  This
puts the value of the quiz questions to the left of those questions.

@example
\newcommand@{\pts@}[1]@{\makebox[0em][r]@{#1 points\hspace*@{1em@}@}@}
\pts@{10@}What is the air-speed velocity of an unladen swallow?

\pts@{90@}An African or European swallow?
@end example

@noindent
@PkgIndex{TikZ}
@PkgIndex{Asymptote}
The right edge of the output @samp{10 points } (note the ending space)
will be just before the @samp{What} (note the space after
@samp{points}).  You can use @code{\makebox} similarly when making
graphics, such as in @file{TikZ} or @file{Asymptote}, where you put the
edge of the text at a known location, regardless of the length of that
text.

For boxes with frames see@tie{}@ref{\fbox & \framebox}. For colors
see@tie{}@ref{Colored boxes}.

There is a related version of @code{\makebox} that is used within the
@code{picture} environment, where the length is given in terms of
@code{\unitlength} (@pxref{\makebox (picture)}).

If you put a double-backslash into @var{text} then @LaTeX{} will not
give you a new line; for instance @code{\makebox@{abc def \\ ghi@}}
outputs @samp{abc defghi} while @code{\makebox@{abc def \par ghi@}}
outputs @samp{abc def ghi}, but neither go to a second line.  To get
multiple lines see@tie{}@ref{\parbox} and@tie{}@ref{minipage}.


@node \fbox & \framebox
@section @code{\fbox} & @code{\framebox}

@findex \fbox
@findex \framebox

Synopses, one of:

@example
\fbox@{@var{text}@}
\framebox@{@var{text}@}
\framebox[@var{width}]@{@var{text}@}
\framebox[@var{width}][@var{position}]@{@var{text}@}
@end example

Create a box with an enclosing frame, four lines surrounding the space.
These commands are the same as @code{\mbox} and @code{\makebox} except
for the frame (@pxref{\mbox & \makebox}). The @code{\fbox} command is
robust, the @code{\framebox} command is fragile (@pxref{\protect}).

@example
\fbox@{Warning! No work shown, no credit given.@}
@end example

@noindent
@LaTeX{} puts the text into a box that cannot be split or hyphenated.
Around that box, separated from it by a small gap, are four lines making
a frame.

The first two command invocations, @code{\fbox@{...@}} and
@code{\framebox@{...@}}, are roughly the same.  As to the third and
fourth invocations, the optional arguments allow you to specify the box
width as @var{width} and the position of the text inside that box as
@var{position}.  @xref{\mbox & \makebox} for the full description but
here is an example creating an empty box that is 1/4@dmn{in} wide.

@example
\setlength@{\fboxsep@}@{0pt@}\framebox[0.25in]@{\strut@}@}
@end example

@noindent
The @code{\strut} inserts a vertical height of @code{\baselineskip}
(@pxref{\strut}).

These parameters determine the frame layout.

@ftable @code
@anchor{fbox framebox fboxrule}
@item \fboxrule
@findex frame, line width
@findex frame rule width
@cindex \fboxrule
The thickness of the lines around the enclosed box.  The default is
0.2@dmn{pt}.  Change it with a command such as
@code{\setlength@{\fboxrule@}@{0.8pt@}} (@pxref{\setlength}).

@anchor{fbox framebox fboxsep}
@item \fboxsep
@findex frame, separation from contents
@cindex \fboxsep
The distance from the frame to the enclosed box. The default is 3@dmn{pt}.
Change it with a command such as @code{\setlength@{\fboxsep@}@{0pt@}}
(@pxref{\setlength}).  Setting it to 0@dmn{pt} is useful sometimes:
this will put a frame around the picture with no white border.

@example
@{\setlength@{\fboxsep@}@{0pt@}
 \framebox@{%
   \includegraphics[width=0.5\textwidth]@{prudence.jpg@}@}@}
@end example

@noindent
The extra curly braces keep the effect of the @code{\setlength} local.

@end ftable

As with @code{\mbox} and @code{\makebox}, @LaTeX{} will not break lines
in @var{text}.  But this example has @LaTeX{} break lines to make a
paragraph, and then frame the result.

@example
\framebox@{%
  \begin@{minipage@}@{0.6\linewidth@}
    My dear, here we must run as fast as we can, just to stay in place.
    And if you wish to go anywhere you must run twice as fast as that.
  \end@{minipage@}@}
@end example

@xref{Colored boxes} for colors other than black and white.

The @code{picture} environment has a version of this command where the
units depend on @code{picture}'s @code{\unitlength} (@pxref{\framebox
(picture)}).


@node \parbox
@section @code{\parbox}

@findex \parbox
@cindex paragraph mode
@cindex paragraph, in a box

Synopses, one of:

@example
\parbox@{@var{width}@}@{@var{contents}@}
\parbox[@var{position}]@{@var{width}@}@{@var{contents}@}
\parbox[@var{position}][@var{height}]@{@var{width}@}@{@var{contents}@}
\parbox[@var{position}][@var{height}][@var{inner-pos}]@{@var{width}@}@{@var{contents}@}
@end example

Produce a box of text that is @var{width} wide. Use this command to make
a box of small pieces of text, of a single paragraph.  This command is
fragile (@pxref{\protect}).

@example
\begin@{picture@}(0,0)
  ...
  \put(1,2)@{\parbox@{1.75in@}@{\raggedright Because the graph is a line on
                         this semilog paper, the relationship is
                         exponential.@}@}
\end@{picture@}
@end example

The @var{contents} are processed in a text mode (@pxref{Modes}) so
@LaTeX{} will break lines to make a paragraph.  But it won't make
multiple paragraphs; for that, use a @code{minipage} environment
(@pxref{minipage}).

The options for @code{\parbox} (except for @var{contents}) are the same
as those for @code{minipage}.  For convenience a summary of the options
is here but see@tie{}@ref{minipage} for a complete description.

There are two required arguments.  The @var{width} is a rigid length
(@pxref{Lengths}).  It sets the width of the box into which @LaTeX{}
typesets @var{contents}.  The @var{contents} is the text that is placed
in that box.  It should not have any paragraph-making components.

There are three optional arguments, @var{position}, @var{height}, and
@var{inner-pos}.  The @var{position} gives the vertical alignment of the
@code{parbox} with respect to the surrounding material.  The possible
values are @code{c} or @code{m} to make the vertical center of the
@code{parbox} lines up with the center of the adjacent line (this is the
default), or @code{t} to match the top line of the @code{parbox} with
the baseline of the surrounding material, or @code{b} to match the
bottom line.

The optional argument @var{height} overrides the natural height of the
box.

The optional argument @var{inner-pos} controls the placement of
@var{content} inside the @code{parbox}. Its default is the value of
@var{position}.  Its possible values are: @code{t} to put the
@var{content} at the top of the box, @code{c} to put it in the vertical
center, @code{b} to put it at the bottom of the box, and @code{s} to
stretch it out vertically (for this, the text must contain vertically
stretchable space).

@node \raisebox
@section @code{\raisebox}

@findex \raisebox

Synopsis, one of:

@example
\raisebox@{@var{distance}@}@{@var{text}@}
\raisebox@{@var{distance}@}[@var{height}]@{@var{text}@}
\raisebox@{@var{distance}@}[@var{height}][@var{depth}]@{@var{text}@}
@end example

Raise or lower @var{text}. This command is fragile (@pxref{\protect}).

This example makes a command for the restriction of a function by
lowering the vertical bar symbol.

@c credit: egreg https://tex.stackexchange.com/a/278631/121234
@example
\newcommand\restricted[1]@{\raisebox@{-.5ex@}@{$|$@}_@{#1@}@}
$f\restricted@{A@}$
@end example

The first mandatory argument @var{distance} specifies how far to raise
the second mandatory argument @var{text}. This is a rigid length
(@pxref{Lengths}).  If it is negative then it lowers @var{text}.  The
@var{text} is processed in LR mode so it cannot contain line breaks
(@pxref{Modes}).

The optional arguments @var{height} and @var{depth} are dimensions.  If
they are specified, they override the natural height and depth of the
box @LaTeX{} gets by typesetting @var{text}.

@anchor{raisebox depth}
@anchor{raisebox height}
@anchor{raisebox width}
@anchor{raisebox totalheight}
In the arguments @var{distance}, @var{height}, and @var{depth} you can
use the following lengths that refer to the dimension of the box that
@LaTeX{} gets on typesetting @var{text}: @code{\depth}, @code{\height},
@code{\width}, @code{\totalheight} (this is the box's height plus its
depth).

This will align two graphics on their top (@pxref{Graphics}).

@c credit: FAQ https://texfaq.org/FAQ-topgraph
@example
\usepackage@{graphicx@} \usepackage@{calc@}  % in preamble
   ...
\begin@{center@}
  \raisebox@{1ex-\height@}@{%
    \includegraphics[width=0.4\linewidth]@{lion.png@}@}
  \qquad
  \raisebox@{1ex-\height@}@{%
    \includegraphics[width=0.4\linewidth]@{meta.png@}@}
\end@{center@}
@end example

@noindent
The first @code{\height} is the height of @file{lion.png} while the
second is the height of @file{meta.png}.


@node \sbox & \savebox
@section @code{\sbox} & @code{\savebox}

@findex \sbox
@findex \savebox
@cindex box, save

Synopsis, one of:

@example
\sbox@{@var{box-cmd}@}@{@var{text}@}
\savebox@{@var{box-cmd}@}@{@var{text}@}
\savebox@{@var{box-cmd}@}[@var{width}]@{@var{text}@}
\savebox@{@var{box-cmd}@}[@var{width}][@var{pos}]@{@var{text}@}
@end example

Typeset @var{text} just as with @code{\makebox} (@pxref{\mbox &
\makebox}) except that @LaTeX{} does not output it but instead saves it
in a storage bin named @var{box-cmd}.  The bin name @var{box-cmd} begins
with a backslash, @code{\}.  You must have previously allocated the bin
@var{box-cmd} with @code{\newsavebox} (@pxref{\newsavebox}).The
@code{\sbox} command is robust while @code{\savebox} is fragile
(@pxref{\protect}).

This creates and uses a bin.

@example
\newsavebox@{\fullname@}
\sbox@{\fullname@}@{John Jacob Jingleheimer Schmidt@}
  ...
\usebox@{\fullname@}! His name is my name, too!
Whenever we go out, the people always shout!
There goes \\usebox@{\fullname@}!  Ya da da da da da da.
@end example

@noindent
One advantage of using and reusing a bin over a @code{\newcommand} is
efficiency, that @LaTeX{} need not repeatedly retypeset the contents.
See the example below.

The first two command invocations,
@code{\sbox@{@var{box-cmd}@}@{@var{text}@}} and
@code{\savebox@{@var{box-cmd}@}@{@var{text}@}}, are roughly equivalent.
As to the third and fourth, the optional arguments allow you to specify
the box width as @var{width}, and the position of the text inside that
box as @var{position}.  @xref{\mbox & \makebox} for the full
description.

In the @code{\sbox} and @code{\savebox} commands the @var{text} is
typeset in LR mode so it does not have line breaks (@pxref{Modes}).  If
you use these then @LaTeX{} doesn't give you an error but it ignores
what you want: if you enter @code{\sbox@{\newbin@}@{test \\ test@}} and
@code{\usebox@{\newbin@}} then you get @samp{testtest}, while if you
enter @code{\sbox@{\newbin@}@{test \par test@}} and
@code{\usebox@{\newbin@}} then you get @samp{test test}, but no error or
warning.  To fix this use a @code{\parbox} or @code{minipage} as here.

@c credit: egreg https://tex.stackexchange.com/a/41668/121234
@example
\savebox@{\abin@}@{%
  \begin@{minipage@}@{\linewidth@}
    \begin@{enumerate@}
      \item First item
      \item Second item
    \end@{enumerate@}
  \end@{minipage@}@}
  ...
\usebox@{\abin@}
@end example

As an example of the efficiency of reusing a bin's contents, this puts
the same picture on each page of the document by putting it in the
header.  @LaTeX{} only typesets it once.

@example
\usepackage@{graphicx@}  % all this in the preamble
\newsavebox@{\sealbin@}
\savebox@{\sealbin@}@{%
  \setlength@{\unitlength@}@{1in@}%
  \begin@{picture@}(0,0)%
     \put(1.5,-2.5)@{%
       \begin@{tabular@}@{c@}
          \includegraphics[height=2in]@{companylogo.png@} \\
          Office of the President
       \end@{tabular@}@}
  \end@{picture@}%
@}
\markright@{\usebox@{\sealbin@}@}
\pagestyle@{headings@}
@end example

@noindent
The @code{picture} environment is good for fine-tuning the placement.

If the bin has not already been defined then you get something like
@samp{Undefined control sequence. <argument> \nobin}.


@node lrbox
@section @code{lrbox}

@findex lrbox

Synopsis:

@example
\begin@{lrbox@}@{@var{box-cmd}@} 
  @var{text}
\end@{lrbox@}
@end example

The @var{text} inside the environment is saved in the bin
@code{@var{box-cmd}}.  The @var{box-cmd} must begin with a
backslash. You must create this bin in advance with @code{\newsavebox}
(@pxref{\newsavebox}).  This is the environment form of the @code{\sbox}
and @code{\savebox} commands, and is equivalent to them. @xref{\sbox &
\savebox} for the full information.

In this example the environment is convenient for entering the
@code{tabular}.

@example
\newsavebox@{\jhbin@}
\begin@{lrbox@}@{\jhbin@}
  \begin@{tabular@}@{c@}
    \includegraphics[height=1in]@{jh.png@} \\
    Jim Hef@{@}feron
  \end@{tabular@}
\end@{lrbox@}    
  ...
\usebox@{\jhbin@}
@end example


@node \usebox
@section @code{\usebox}

@findex \usebox
@cindex box, use saved box

Synopsis:

@example
\usebox@{@var{box-cmd}@}
@end example

Produce the box most recently saved in the bin @var{box-cmd} by the
commands @code{\sbox} or @code{\savebox}, or the @code{lrbox}
environment. @xref{\sbox & \savebox} for more information and examples.
(Note that @var{box-cmd} starts with a backslash.)  This command is
robust (@pxref{\protect}).


@node Color
@chapter Color

@cindex color

You can add color to text, rules, etc.  You can also have color in a box
or on an entire page and write text on top of it.

Color support comes as an additional package.  So put
@code{\usepackage@{color@}} in your document preamble to use the
commands described here.

Many other packages also supplement @LaTeX{}'s color abilities.
Particularly worth mentioning is @file{xcolor}, which is widely used and
significantly extends the capabilities described here, including adding
@samp{HTML} and @samp{Hsb} color models.

@menu
* Color package options::       Options when you load the standard package.
* Color models::                How colors are represented.
* Commands for color::          The available commands.
@end menu


@node Color package options
@section @code{color} package options

@cindex color package options
@cindex options, color package

Synopsis (must be in the document preamble):

@example
\usepackage[@var{comma-separated option list}]@{color@}
@end example

When you load the @file{color} package there are two kinds of available
options.

The first specifies the @dfn{printer driver}.  @LaTeX{} doesn't contain
information about different output systems but instead depends on
information stored in a file.  Normally you should not specify the
driver option in the document, and instead rely on your system's
default. One advantage of this is that it makes the document portable
across systems.  For completeness we include a list of the drivers.  The
currently relevant ones are: @file{dvipdfmx}, @file{dvips},
@file{dvisvgm}, @file{luatex}, @file{pdftex}, @file{xetex}.  The two
@file{xdvi} and @file{oztex} are essentially aliases for @file{dvips}
(and @file{xdvi} is monochrome).  Ones that should not be used for new
systems are: @file{dvipdf}, @file{dvipdfm}, @file{dviwin},
@file{dvipsone}, @file{emtex}, @file{pctexps}, @file{pctexwin},
@file{pctexhp}, @file{pctex32}, @file{truetex}, @file{tcidvi},
@file{vtex} (and @file{dviwindo} is an alias for @file{dvipsone}).

The second kind of options, beyond the drivers, are below.

@table @code

@item monochrome
Disable the color commands, so that they do not generate errors but do
not generate color either.

@item dvipsnames
Make available a list of 68 color names that are often used,
particularly in legacy documents.  These color names were originally
provided by the @file{dvips} driver, giving the option name.

@item nodvipsnames
Do not load that list of color names, saving @LaTeX{} a tiny amount of
memory space.

@end table


@node Color models
@section Color models

@cindex color models

A @dfn{color model} is a way of representing colors.  @LaTeX{}'s
capabilities depend on the printer driver.  However, the @file{pdftex},
@file{xetex}, and @file{luatex} printer drivers are today by far the
most commonly used.  The models below work for those drivers.  All but
one of these is also supported by essentially all other printer drivers
used today.

Note that color combination can be additive or subtractive.  Additive
mixes colors of light, so that for instance combining full intensities
of red, green, and blue produces white.  Subtractive mixes pigments,
such as with inks, so that combining full intensity of cyan, magenta,
and yellow makes black.

@table @code
@anchor{color models cmyk}
@item cmyk
A comma-separated list with four real numbers between 0 and 1,
inclusive.  The first number is the intensity of cyan, the second is
magenta, and the others are yellow and black.  A number value of 0 means
minimal intensity, while a 1 is for full intensity.  This model is often
used in color printing.  It is a subtractive model.

@anchor{color models gray}
@item gray
A single real number between 0 and 1, inclusive.  The colors are shades
of grey.  The number 0 produces black while 1 gives white.

@anchor{color models rgb}
@item rgb
A comma-separated list with three real numbers between 0 and 1,
inclusive.  The first number is the intensity of the red component, the
second is green, and the third the blue.  A number value of 0 means that
none of that component is added in, while a 1 means full intensity.
This is an additive model.

@anchor{color models RGB}
@item RGB
(@file{pdftex}, @file{xetex}, @file{luatex} drivers) A comma-separated
list with three integers between 0 and 255, inclusive.  This model is a
convenience for using @code{rgb} since outside of @LaTeX{} colors are
often described in a red-green-blue model using numbers in this range.
The values entered here are converted to the @code{rgb} model by
dividing by 255.

@anchor{color models named}
@item named
Colors are accessed by name, such as @samp{PrussianBlue}.  The list of
names depends on the driver, but all support the names @samp{black},
@samp{blue}, @samp{cyan}, @samp{green}, @samp{magenta}, @samp{red},
@samp{white}, and @samp{yellow} (See the @code{dvipsnames} option in
@ref{Color package options}).

@end table


@node Commands for color
@section Commands for color

@cindex color package commands

These are the commands available with the @file{color} package.

@menu
* Define colors::            Give a color a name.
* Colored text::             Text or rules in color.
* Colored boxes::            A box of color, to write over.
* Colored pages::            A whole page colored.
@end menu


@node Define colors
@subsection Define colors

@cindex color
@cindex define color
@cindex color, define 

Synopsis:

@example
\definecolor@{@var{name}@}@{@var{model}@}@{@var{specification}@}
@end example

Give the name @var{name} to the color.  For example, after this

@example
\definecolor@{silver@}@{rgb@}@{0.75,0.75,0.74@}
@end example

@noindent
you can use that color name with @code{Hi ho,
\textcolor@{silver@}@{Silver@}!}.

This example gives the color a more abstract name, so it could change and
not be misleading.

@example
\definecolor@{logocolor@}@{RGB@}@{145,92,131@}    % RGB needs pdflatex
\newcommand@{\logo@}@{\textcolor@{logocolor@}@{Bob's Big Bagels@}@}
@end example

Often a document's colors are defined in the preamble, or in the class
or style, rather than in the document body.


@node Colored text
@subsection Colored text

@cindex color
@cindex colored text

Synopses:

@example
\textcolor@{@var{name}@}@{...@}
\textcolor[@var{color model}]@{@var{color specification}@}@{...@}
@end example

@noindent
or

@example
\color@{@var{name}@}
\color[@var{color model}]@{@var{specification}@}
@end example

The affected text gets the color.  This line

@example
\textcolor@{magenta@}@{My name is Ozymandias, king of kings:@}
Look on my works, ye Mighty, and despair!
@end example

@noindent
causes the first half to be in magenta while the rest is in black.  You
can use a color declared with @code{\definecolor} in exactly the same
way that we just used the builtin color @samp{magenta}.

@example
\definecolor@{MidlifeCrisisRed@}@{rgb@}@{1.0,0.11,0.0@}
I'm thinking about getting a \textcolor@{MidlifeCrisisRed@}@{sports car@}.
@end example

The two @code{\textcolor} and @code{\color} differ in that the first is
a command form, enclosing the text to be colored as an argument.  Often
this form is more convenient, or at least more explicit.  The second
form is a declaration, as in @code{The moon is made of @{\color@{green@}
green@} cheese}, so it is in effect until the end of the current group
or environment.  This is sometimes useful when writing macros or as
below where it colors everything inside the @code{center} environment,
including the vertical and horizontal lines.

@example
\begin@{center@} \color@{blue@}
  \begin@{tabular@}@{l|r@}
    UL &UR \\ \hline
    LL &LR 
  \end@{tabular@}
\end@{center@}
@end example

You can use color in equations.  A document might have this definition
in the preamble

@example
\definecolor@{highlightcolor@}@{RGB@}@{225,15,0@}
@end example

@noindent
and then contain this equation.

@example
\begin@{equation@}
  \int_a^b \textcolor@{highlightcolor@}@{f'(x)@}\,dx=f(b)-f(a)
\end@{equation@}
@end example

Typically the colors used in a document are declared in a class or style
but sometimes you want a one-off.  Those are the second forms in the
synopses.

@example
Colors of \textcolor[rgb]@{0.33,0.14,0.47@}@{Purple@} and
@{\color[rgb]@{0.72,0.60,0.37@} Gold@} for the team.
@end example

The format of @var{color specification } depends on the color model
(@pxref{Color models}).  For instance, while @code{rgb} takes three
numbers, @code{gray} takes only one.

@example
The selection was \textcolor[gray]@{0.5@}@{grayed out@}.
@end example

Colors inside colors do not combine.  Thus

@example
\textcolor@{green@}@{kind of \textcolor@{blue@}@{blue@}@}
@end example

@noindent
has a final word that is blue, not a combination of blue and green.

@c xx address coloring a line of a table?


@node Colored boxes
@subsection Colored boxes

@cindex color
@cindex colored boxes
@cindex box, colored

Synopses:

@example
\colorbox@{@var{name}@}@{...@}
\colorbox[@var{model name}]@{@var{box background color}@}@{...@}
@end example

@noindent
or

@example
\fcolorbox@{@var{frame color}@}@{@var{box background color}@}@{...@}
\fcolorbox[@var{model name}]@{@var{frame color}@}@{@var{box background color}@}@{...@}
@end example

Make a box with the stated background color.  The @code{\fcolorbox}
command puts a frame around the box.  For instance this

@example
Name:~\colorbox@{cyan@}@{\makebox[5cm][l]@{\strut@}@}
@end example

@noindent
makes a cyan-colored box that is five centimeters long and gets its
depth and height from the @code{\strut} (so the depth is
@code{-.3\baselineskip} and the height is @code{\baselineskip}).  This
puts white text on a blue background.

@example
\colorbox@{blue@}@{\textcolor@{white@}@{Welcome to the machine.@}@}
@end example

The @code{\fcolorbox} commands use the same parameters as @code{\fbox}
(@pxref{\fbox & \framebox}), @code{\fboxrule} and @code{\fboxsep}, to
set the thickness of the rule and the boundary between the box interior
and the surrounding rule.  @LaTeX{}'s defaults are @code{0.4pt} and
@code{3pt}, respectively.

This example changes the thickness of the border to 0.8 points.  Note
that it is surrounded by curly braces so that the change ends at the end
of the second line.

@example
@{\setlength@{\fboxrule@}@{0.8pt@}
\fcolorbox@{black@}@{red@}@{Under no circumstances turn this knob.@}@}
@end example


@node Colored pages
@subsection Colored pages

@cindex color
@cindex colored page
@cindex page, colored 
@cindex background, colored

Synopses:

@example
\pagecolor@{@var{name}@}
\pagecolor[@var{color model}]@{@var{color specification}@}
\nopagecolor
@end example

The first two set the background of the page, and all subsequent pages,
to the color.  For an explanation of the specification in the second
form @pxref{Colored text}.  The third returns the background to normal,
which is a transparent background.  (If that is not supported use
@code{\pagecolor@{white@}}, although that will make a white background
rather than the default transparent background.)

@example
 ...
\pagecolor@{cyan@}
 ...
\nopagecolor
@end example


@node Graphics
@chapter Graphics

@cindex graphics
@cindex graphics package

You can use graphics such as PNG or PDF files in your @LaTeX{} document.
You need an additional package, which comes standard with @LaTeX{}.
This example is the short how-to.

@example
\include@{graphicx@}  % goes in the preamble
  ...
\includegraphics[width=0.5\linewidth]@{plot.pdf@}
@end example

To use the commands described here your document preamble must contain
either @code{\usepackage@{graphicx@}} or
@code{\usepackage@{graphics@}}. Most of the time, @file{graphicx} is the
better choice.

Graphics come in two main types, raster and vector.  @LaTeX{} can use
both.  In raster graphics the file contains an entry for each location
in an array, describing what color it is.  An example is a photograph,
in JPG format.  In vector graphics, the file contains a list of
instructions such as @samp{draw a circle with this radius and that
center}.  An example is a line drawing produced by the Asymptote
program, in PDF format.  Generally vector graphics are more useful
because you can rescale their size without pixelation or other problems,
and because they often have a smaller size.

There are systems particularly well-suited to make graphics for a
@LaTeX{} document.  For example, these allow you to use the same fonts
as in your document.  @LaTeX{} comes with a @code{picture} environment
(@pxref{picture}) that has simple capabilities.  Besides that, there are
other ways to include the graphic-making commands in the document.  Two
such systems are the PSTricks and TikZ packages.  There are also systems
external to @LaTeX{}, that generate a graphic that you include using the
commands of this chapter.  Two that use a programming language are
Asymptote and MetaPost.  One that uses a graphical interface is Xfig.
Full description of these systems is outside the scope of this document;
see their documentation on CTAN.

@menu
* Graphics package options::         Options when you load the package.
* Graphics package configuration::   Where to look for files, which file types.
* Commands for graphics::            The available commands.
@end menu


@node Graphics package options
@section @code{graphics} package options

@cindex graphics package options
@cindex options, graphics package

Synopsis (must be in the document preamble):

@example
\usepackage[@var{comma-separated option list}]@{graphics@}
@end example

@noindent
or

@example
\usepackage[@var{comma-separated option list}]@{graphicx@}
@end example

The @code{graphicx} package has a format for optional arguments to the
@code{\includegraphics} command that is convenient (it is the key-value
format), so it is the better choice for new documents.  When you load
the @file{graphics} or @file{graphicx} package with @code{\usepackage}
there are two kinds of available options.

The first is that @LaTeX{} does not contain information about different
output systems but instead depends on information stored in a
@dfn{printer driver} file.  Normally you should not specify the driver
option in the document, and instead rely on your system's default. One
advantage of this is that it makes the document portable across systems.

For completeness here is a list of the drivers.  The currently relevant
ones are: @file{dvipdfmx}, @file{dvips}, @file{dvisvgm}, @file{luatex},
@file{pdftex}, @file{xetex}.  The two @file{xdvi} and @file{oztex} are
essentially aliases for @file{dvips} (and @file{xdvi} is monochrome).
Ones that should not be used for new systems are: @file{dvipdf},
@file{dvipdfm}, @file{dviwin}, @file{dvipsone}, @file{emtex},
@file{pctexps}, @file{pctexwin}, @file{pctexhp}, @file{pctex32},
@file{truetex}, @file{tcidvi}, @file{vtex} (and @file{dviwindo} is an
alias for @file{dvipsone}).  These are stored in files with a
@file{.def} extension, such as @file{pdftex.def}.

The second kind of options are below.

@table @code
@item demo
Instead of an image file, @LaTeX{} puts in a 150@tie{}pt by 100@tie{}pt
rectangle (unless another size is specified in the
@code{\includegraphics} command).

@item draft
For each graphic file, it is not shown but instead the file name is
printed in a box of the correct size.  In order to determine the size,
the file must be present.

@item final
(Default) Override any previous @code{draft} option, so that the
document shows the contents of the graphic files.

@item hiderotate
Do not show rotated text.  (This allows for the possibility that a
previewer does not have the capability to rotate text.)
@c what does it show?

@item hidescale
Do not show scaled text.  (This allows for the possibility that a
previewer does not have the capability to scale.)
@c what does it show?

@item hiresbb
In a PS or EPS file the graphic size may be specified in two ways.  The
@code{%%BoundingBox} lines describe the graphic size using integer
multiples of a PostScript point, that is, integer multiples of 1/72
inch.  A later addition to the PostScript language allows decimal
multiples, such as 1.23, in @code{%%HiResBoundingBox} lines.  This
option has @LaTeX{} to read the size from the latter.

@end table


@node Graphics package configuration
@section  @code{graphics} package configuration

@cindex graphics
@cindex graphics package
@cindex configuration, graphics package
@cindex EPS files
@cindex JPEG files
@cindex JPG files
@cindex PDF graphic files
@cindex PNG files

These commands configure the way @LaTeX{} searches the file system for
the graphic.

The behavior of file system search code is necessarily platform
dependent.  In this document we cover GNU/Linux, Macintosh, and Windows, as
those systems are typically configured.  For other situations consult
the documentation in @file{grfguide.pdf}, or the @LaTeX{} source, or your
@TeX{} distribution's documentation.

@menu
* \graphicspath::                Directories to search.
* \DeclareGraphicsExtensions::   File types, such as JPG or EPS.
* \DeclareGraphicsRule::         How to handle file types.
@end menu


@node \graphicspath
@subsection @code{\graphicspath}

@findex \graphicspath

Synopsis:

@example
\graphicspath@{@var{list of dir names inside curly brackets}@}
@end example

Declare a list of directories to search for graphics files.  This allows
you to later say something like @code{\includegraphics@{lion.png@}}
instead of having to give its path.

@LaTeX{} always looks for graphic files first in the current directory.
The declaration below tells the system to then look in the subdirectory
@file{pix}, and then @file{../pix}.

@example
\usepackage@{graphicx@}   % or graphics; put in preamble
  ...
\graphicspath@{ @{pix/@} @{../pix/@} @}
@end example

The @code{\graphicspath} declaration is optional.  If you don't include
it then @LaTeX{}'s default is to search all of the places that it
usually looks for a file (it uses @LaTeX{}'s @code{\input@@path}).  In
particular, in this case one of the places it looks is the current
directory.

Enclose each directory name in curly braces; for example, above it says
@samp{@code{@{pix@}}}.  Do this even if there is only one directory.
Each directory name must end in a forward slash, @file{/}.  This is true
even on Windows, where good practice is to use forward slashes for all
the directory separators since it makes the document portable to other
platforms.  If you have spaces in your directory name then use double
quotes, as with @code{@{"my docs/"@}}. Getting one of these rules wrong
will cause @LaTeX{} to report @code{Error: File `@var{filename}' not
found}.

Basically, the algorithm is that with this example, after looking in the
current directory,

@example
\graphicspath@{ @{pix/@} @{../pix/@} @}
...
\usepackage@{lion.png@}
@end example

@noindent
for each of the listed directories, @LaTeX{} concatenates it with the
file name and searches for the result, checking for @file{pix/lion.png}
and then @file{../pix/lion.png}.  This algorithm means that the
@code{\graphicspath} command does not recursively search subdirectories:
if you issue @code{\graphicspath@{@{a/@}@}} and the graphic is in
@file{a/b/lion.png} then @LaTeX{} will not find it.  It also means that
you can use absolute paths such as
@code{\graphicspath@{@{/home/jim/logos/@}@}} or
@code{\graphicspath@{@{C:/Users/Albert/Pictures/@}@}}.  However, using
these means that the document is not portable.  (You could preserve
portability by adjusting your @TeX{} system settings configuration file
parameter @code{TEXINPUTS}; see the documentation of your system.)

You can use @code{\graphicspath} anywhere in the document.  You can use
it more than once.  Show its value with
@code{\makeatletter\typeout@{\Ginput@@path@}\makeatother}.

The directories are taken with respect to the base file.  That is,
suppose that you are working on a document based on @file{book/book.tex}
and it contains @code{\include@{chapters/chap1@}}.  If in
@file{chap1.tex} you put @code{\graphicspath@{@{plots/@}@}} then
@LaTeX{} will not search for graphics in @file{book/chapters/plots}, but
instead in @file{book/plots}.


@node \DeclareGraphicsExtensions
@subsection @code{\DeclareGraphicsExtensions}

@findex \DeclareGraphicsExtensions

Synopses:

@example
\DeclareGraphicsExtensions@{@var{comma-separated list of file extensions}@}
@end example

Declare the filename extensions to try.  This allows you to specify the
order in which to choose graphic formats when you include graphic files
by giving the filename without the extension, as in
@code{\includegraphics@{functionplot@}}.

In this example, @LaTeX{} will find files in the PNG format before PDF
files.

@example
\DeclareGraphicsExtensions@{.png,PNG,.pdf,.PDF@}
  ...
\includegraphics@{lion@}   % will find @file{lion.png} before @file{lion.pdf} 
@end example

@noindent
Because the file name @file{lion} does not have a period, @LaTeX{} uses
the extension list.  For each directory in the graphics path
(@pxref{\graphicspath}), @LaTeX{} will try the extensions in the order
given.  If it does not find such a file after trying all the directories
and extensions then it reports @samp{! LaTeX Error: File `@file{lion}'
not found}.  Note that you must include the periods at the start of the
extensions.

Because GNU/Linux and Macintosh filenames are case sensitive, the list of
file extensions is case sensitive on those platforms.  The Windows
platform is not case sensitive.

You are not required to include @code{\DeclareGraphicsExtensions} in
your document; the printer driver has a sensible default.  For example,
the most recent @file{pdftex.def} has this extension list.

@example
.png,.pdf,.jpg,.mps,.jpeg,.jbig2,.jb2,.PNG,.PDF,.JPG,.JPEG,.JBIG2,.JB2
@end example

You can use this command anywhere in the document.  You can use it more
than once.  Show its value with
@code{\makeatletter\typeout@{\Gin@@extensions@}\makeatother}.


@node \DeclareGraphicsRule
@subsection @code{\DeclareGraphicsRule}

@findex \DeclareGraphicsRule

Synopsis:

@example
\DeclareGraphicsRule@{@var{extension}@}@{@var{type}@}@{@var{size-file extension}@}@{@var{command}@}
@end example

Declare how to handle graphic files whose names end in @var{extension}.

This example declares that all files with names have the form
@file{filename-without-dot.mps} will be treated as output from MetaPost,
meaning that the printer driver will use its MetaPost-handling code to
input the file.

@example
\DeclareGraphicsRule@{.mps@}@{mps@}@{.mps@}@{@}
@end example

This

@example
\DeclareGraphicsRule@{*@}@{mps@}@{*@}@{@}
@end example

@noindent
tells @LaTeX{} that it should handle as MetaPost output any file with an
extension not covered by another rule, so it covers @file{filename.1},
@file{filename.2}, etc.

This describes the four arguments.

@table @var
@item extension
The file extension to which this rule applies. The extension is anything
after and including the first dot in the filename.  Use the Kleene star,
@code{*}, to denote the default behaviour for all undeclared extensions.

@item type
The type of file involved.  This type is a string that must be defined
in the printer driver. For instance, files with extensions @file{.ps},
@file{.eps}, or @file{.ps.gz} may all be classed as type @code{eps}.
All files of the same type will be input with the same internal command
by the printer driver. For example, the file types that @file{pdftex}
recognizes are: @code{jpg}, @code{jbig2}, @code{mps}, @code{pdf},
@code{png}, @code{tif}.

@item size-file extension
The extension of the file to be read to determine the size of the
graphic, if there is such a file. It may be the same as @var{extension}
but it may be different.

As an example, consider a PostScript graphic.  To make it smaller, it
might be compressed into a @file{.ps.gz} file.  Compressed files are not
easily read by @LaTeX{} so you can put the bounding box information in a
separate file. If @var{size-file extension} is empty then you must
specify size information in the arguments of @code{\includegraphics}.

If the driver file has a procedure for reading size files for
@code{type} then that will be used, otherwise it will use the procedure
for reading @file{.eps} files.  (Thus you may specify the size of bitmap
files in a file with a PostScript style @code{%%BoundingBox} line if no
other format is available.)

@item command
A command that will be applied to the
file. This is very often left blank. This command must start with a
single backward quote.  Thus,
@code{\DeclareGraphicsRule@{.eps.gz@}@{eps@}@{.eps.bb@}@{`gunzip -c
#1@}} specifies that any file with the extension @file{.eps.gz} should
be treated as an @code{eps} file, with the BoundingBox information
stored in the file with extension @file{.eps.bb}, and that the command
@code{gunzip -c} will run on your platform to decompresses the file.

Such a command is specific to your platform.  In addition, your @TeX{}
system must allow you to run external commands; as a security measure
modern systems restrict running commands unless you explicitly allow it.
See the documentation for your @TeX{} distribution.

@end table

@node Commands for graphics
@section Commands for graphics

@cindex graphics package commands
@cindex commands, graphics package

These are the commands available with the @file{graphics} and
@file{graphicx} packages.

@menu
* \includegraphics::     Using a graphic in your document.
* \rotatebox::           Rotating boxes, including graphics.
* \scalebox::            Scaling boxes, including graphics.
* \resizebox::           Scaling boxes, including graphics, to a set size.
@end menu


@node \includegraphics
@subsection @code{\includegraphics}

@cindex graphics
@cindex graphics package
@cindex including graphics
@cindex importing graphics
@cindex EPS files
@cindex JPEG files
@cindex JPG files
@cindex PDF graphic files
@cindex PNG files
@findex \includegraphics

Synopses for @file{graphics} package:

@example
\includegraphics@{@var{filename}@}
\includegraphics[@var{urx},@var{ury}]@{@var{filename}@}
\includegraphics[@var{llx},@var{lly}][@var{urx},@var{ury}]@{@var{filename}@}
\includegraphics*@{@var{filename}@}
\includegraphics*[@var{urx},@var{ury}]@{@var{filename}@}
\includegraphics*[@var{llx},@var{lly}][@var{urx},@var{ury}]@{@var{filename}@}
@end example

Synopses for @file{graphicx} package:

@example
\includegraphics@{@var{filename}@}
\includegraphics[@var{key-value list}]@{@var{filename}@}
\includegraphics*@{@var{filename}@}
\includegraphics*[@var{key-value list}]@{@var{filename}@}
@end example

Include a graphics file.  The starred form @code{\includegraphics*} will
clip the graphic to the size specified, while for the unstarred form any
part of the graphic that is outside the box of the specified size will
over-print the surrounding area.

This 

@example
\usepackage@{graphicx@}  % in preamble
  ...
\begin@{center@}
  \includegraphics@{plot.pdf@}
\end@{center@}
@end example

@noindent
will incorporate into the document the graphic in @file{plot.pdf},
centered and at its nominal size.  You can also give a path to the file,
as with @code{\includegraphics@{graphics/plot.pdf@}}.  To specify a list
of locations to search for the file, @pxref{\graphicspath}.

If your filename includes spaces then put it in double quotes. An example
is @code{\includegraphics@{"sister picture.jpg"@}}.

The @code{\includegraphics@{@var{filename}@}} command decides on the
type of graphic by splitting @var{filename} on the first dot.  You can
use @var{filename} with no dot, as in @code{\includegraphics@{turing@}}
and then @LaTeX{} tries a sequence of extensions such as @code{.png} and
@code{.pdf} until it finds a file with that extension
(@pxref{\DeclareGraphicsExtensions}).

If your file name contains dots before the extension then you can hide
them with curly braces, as in
@code{\includegraphics@{@{plot.2018.03.12.a@}.pdf@}}.  Or, if you use
the @file{graphicx} package then you can use the options @code{type} and
@code{ext}; see below.  This and other filename issues are also handled
with the package @file{grffile}.

This example puts a graphic in a figure environment so @LaTeX{} can
move it to the next page if fitting it on the current page is awkward
(@pxref{figure}).

@example
\begin@{figure@}
  \centering
  \includegraphics[width=3cm]@{lungxray.jpg@}
  \caption@{The evidence is overwhelming: don't smoke.@}  \label@{fig:xray@}
\end@{figure@}
@end example

This places a graphic that will not float, so it is sure to appear at
this point in the document even if makes @LaTeX{} stretch the text or
resort to blank areas on the page.  It will be centered and will have a
caption.

@example
\usepackage@{caption@}  % in preamble
  ...
\begin@{center@}
  \includegraphics@{pix/nix.png@}
  \captionof@{figure@}@{The spirit of the night@} \label@{pix:nix@} % optional
\end@{center@}
@end example

This example puts a box with a graphic side by side with one having
text, with the two vertically centered.

@example
\newcommand*@{\vcenteredhbox@}[1]@{\begin@{tabular@}@{@@@{@}c@@@{@}@}#1\end@{tabular@}@}
  ...
\begin@{center@}
  \vcenteredhbox@{\includegraphics[width=0.4\textwidth]@{plot@}@}
  \hspace@{1em@}
  \vcenteredhbox@{\begin@{minipage@}@{0.4\textwidth@}
                   \begin@{displaymath@}
                     f(x)=x\cdot \sin (1/x)
                   \end@{displaymath@}
                 \end@{minipage@}@}
\end@{center@}
@end example

If you use the @file{graphics} package then the only options involve the
size of the graphic (but see @ref{\rotatebox} and @ref{\scalebox}).
When one optional argument is present then it is
@code{[@var{urx},@var{ury}]} and it gives the coordinates of the top
right corner of the image, as a pair of @TeX{} dimensions (@pxref{Units
of length}).  If the units are omitted they default to @code{bp}.  In
this case, the lower left corner of the image is assumed to be at (0,0).
If two optional arguments are present then the leading one is
@code{[@var{llx},@var{lly}]}, specifying the coordinates of the image's
lower left.  Thus, @code{\includegraphics[1in,0.618in]@{...@}} calls for
the graphic to be placed so it is 1@tie{}inch wide and 0.618@tie{}inches
tall and so its origin is at (0,0).

The @file{graphicx} package gives you many more options.  Specify them
in a key-value form, as here.

@example
\begin@{center@}
  \includegraphics[width=1in,angle=90]@{lion@}
  \hspace@{2em@}
  \includegraphics[angle=90,width=1in]@{lion@}
\end@{center@}
@end example

@noindent
The options are read left-to-right. So the first graphic above is made
one inch wide and then rotated, while the second is rotated and then
made one inch wide.  Thus, unless the graphic is perfectly square, the
two will end with different widths and heights.

There are many options.  The primary ones are listed first.

Note that a graphic is placed by @LaTeX{} into a box, which is
traditionally referred to as its bounding box (distinct from the
PostScript BoundingBox described below).  The graphic's printed area may
go beyond this box, or sit inside this box, but when @LaTeX{} makes up a
page it puts together boxes and this is the box allocated for the
graphic.

@table @code
@anchor{includegraphics width}
@item width
The graphic will be shown so its bounding box is this width.  An example
is @code{\includegraphics[width=1in]@{plot@}}.  You can use the standard
@TeX{} dimensions (@pxref{Units of length}) and also convenient is
@code{\linewidth}, or in a two-column document, @code{\columnwidth}
(@pxref{Page layout parameters}).  An example is that by using the
@file{calc} package you can make the graphic be 1@tie{}cm narrow than
the width of the text with
@code{\includegraphics[width=\linewidth-1.0cm]@{hefferon.jpg@}}.

@item height
@anchor{includegraphics height}
The graphic will be shown so its bounding box is this height.  You can
use the standard @TeX{} dimensions (@pxref{Units of length}), and also
convenient are @code{\pageheight} and @code{\textheight} (@pxref{Page
layout parameters}).  For instance, the command
@code{\includegraphics[height=0.25\textheight]@{godel@}} will make the
graphic a quarter of the height of the text area.

@item totalheight
@anchor{includegraphics totalheght}
The graphic will be shown so its bounding box has this height plus
depth.  This differs from the height if the graphic was rotated. For
instance, if it has been rotated by -90 then it will have zero height
but a large depth.

@item keepaspectratio
@anchor{includegraphics keepaspectratio}
If set to @code{true}, or just specified as here

@example
@code{\includegraphics[...,keepaspectratio,...]@{...@}}
@end example

@noindent
and you give as options both @code{width} and @code{height} (or
@code{totalheight}), then @LaTeX{} will make the graphic is as large as
possible without distortion. That is, @LaTeX{} will ensure that neither
is the graphic wider than @code{width} nor taller than @code{height} (or
@code{totalheight}).

@item scale
Factor by which to scale the graphic.  To make a graphic twice its
nominal size, enter @code{\includegraphics[scale=2.0]@{...@}}.  This
number may be any value; a number between 1 and@tie{}0 will shrink the
graphic and a negative number will reflect it.

@item angle
Rotate the graphic.  The angle is taken in degrees and counterclockwise.
The graphic is rotated about its @code{origin}; see that option.  For a
complete description of how rotated material is typeset,
@pxref{\rotatebox}.

@item origin
The point of the graphic about which the rotation happens.  Possible
values are any string containing one or two of: @code{l} for left,
@code{r} for right, @code{b} for bottom, @code{c} for center, @code{t}
for top, and @code{B} for baseline.  Thus, entering the command
@code{\includegraphics[angle=180,origin=c]@{moon@}} will turn the
picture upside down about that picture's center, while the command
@code{\includegraphics[angle=180,origin=lB]@{LeBateau@}} will turn its
picture upside down about its left baseline.  (The character @code{c}
gives the horizontal center in @code{bc} or @code{tc}, but gives the
vertical center in @code{lc} or @code{rc}.)  The default is @code{lB}.

To rotate about an arbitrary point, @pxref{\rotatebox}.

@end table

These are lesser-used options.

@table @code
@anchor{includegraphics viewport}
@item viewport
Pick out a subregion of the graphic to show.  Takes four arguments,
separated by spaces and given in @TeX{} dimensions, as with
@code{\includegraphics[.., viewport=0in 0in 1in 0.618in]@{...@}}.  The
dimensions default to big points,@tie{}@code{bp}.  They are taken
relative to the origin specified by the bounding box.  See also the
@code{trim} option.

@anchor{includegraphics trim}
@item trim
Gives parts of the graphic to not show.  Takes four arguments, separated
by spaces, that are given in @TeX{} dimensions, as with
@code{\includegraphics[.., trim= 0in 0.1in 0.2in 0.3in, ...]@{...@}}.
These give the amounts of the graphic not to show, that is, @LaTeX{}
will crop the picture by 0@tie{}inches on the left, 0.1@tie{}inches on
the bottom, 0.2@tie{}inches on the right, and 0.3@tie{}inches on the
top.  See also the @code{viewport} option.

@anchor{includegraphics clip}
@item clip
If set to @code{true}, or just specified as here

@example
\includegraphics[...,clip,...]@{...@}
@end example

@noindent
then the graphic is cropped to the bounding box.  This is the same as
using the starred form of the command,
@code{\includegraphics*[...]@{...@}}.

@anchor{includegraphics page}
@item page
Give the page number of a multi-page PDF file.  The default is
@code{page=1}.

@anchor{includegraphics pagebox}
@item pagebox
Specifies which bounding box to use for PDF files from among
@code{mediabox}, @code{cropbox}, @code{bleedbox}, @code{trimbox}, or
@code{artbox}.  PDF files do not have the BoundingBox that PostScript
files have, but may specify up to four predefined rectangles. The
MediaBox gives the boundaries of the physical medium. The CropBox is the
region to which the contents of the page are to be clipped when
displayed.  The BleedBox is the region to which the contents of the page
should be clipped in production. The TrimBox is the intended dimensions
of the finished page.  The ArtBox is the extent of the page's meaningful
content.  The driver will set the image size based on CropBox if
present, otherwise it will not use one of the others, with a
driver-defined order of preference.  MediaBox is always present.

@anchor{includegraphics interpolate}
@item interpolate
Enable or disable interpolation of raster images by the viewer.  Can be
set with @code{interpolate=true} or just specified as here.

@example
\includegraphics[...,interpolate,...]@{...@}
@end example

@anchor{includegraphics quiet}
@item quiet
Do not write information to the log.  You can set it with
@code{quiet=true} or just specified it with
@code{\includegraphics[...,quite,...]@{...@}},

@anchor{includegraphics draft}
@item draft
If you set it with @code{draft=true} or just specify it with

@example
\includegraphics[...,draft,...]@{...@}
@end example

@noindent
then the graphic will not appear in the document, possibly saving color
printer ink.  Instead, @LaTeX{} will put an empty box of the correct
size with the filename printed in it.

@end table

These options address the bounding box for Encapsulated PostScript
graphic files, which have a size specified with a line
@code{%%BoundingBox} that appears in the file.  It has four values,
giving the lower @math{x} coordinate, lower @math{y} coordinate, upper
@math{x} coordinate, and upper @math{y} coordinate.  The units are
PostScript points, equivalent to @TeX{}'s big points, 1/72@tie{}inch.
For example, if an @file{.eps} file has the line @code{%%BoundingBox 10
20 40 80} then its natural size is 30/72@tie{}inch wide by
60/72@tie{}inch tall.

@table @code
@anchor{includegraphics bb}
@item bb
Specify the bounding box of the displayed region.  The argument is four
dimensions separated by spaces, as with @code{\includegraphics[.., bb=
0in 0in 1in 0.618in]@{...@}}.  Usually @code{\includegraphics} reads the
BoundingBox numbers from the EPS file automatically, so this option is
only useful if the bounding box is missing from that file or if you want
to change it.

@anchor{includegraphics bbllx}
@anchor{includegraphics bblly}
@anchor{includegraphics bburx}
@anchor{includegraphics bbury}
@item bbllx, bblly, bburx, bbury
Set the bounding box.  These four are obsolete, but are retained for
compatibility with old packages.

@anchor{includegraphics natwidth}
@anchor{includegraphics natheight}
@item natwidth, natheight
An alternative for @code{bb}.  Setting

@example
\includegraphics[...,natwidth=1in,natheight=0.618in,...]@{...@}
@end example

@noindent
is the same as setting @code{bb=0 0 1in 0.618in}.
 
@anchor{includegraphics hiresbb}
@item hiresbb
If set to @code{true}, or just specified as with

@example
\includegraphics[...,hiresbb,...]@{...@}
@end example

@noindent
then @LaTeX{} will look for @code{%%HiResBoundingBox} lines instead of
@code{%%BoundingBox} lines.  (The @code{BoundingBox} lines use only
natural numbers while the @code{HiResBoundingBox} lines use decimals;
both use units equivalent to @TeX{}'s big points, 1/72@tie{}inch.) To
override a prior setting of @code{true}, you can set it to @code{false}.

@end table

These following options allow a user to override @LaTeX{}'s method of
choosing the graphic type based on the filename extension.  An example
is that @code{\includegraphics[type=png,ext=.xxx,read=.xxx]@{lion@}}
will read the file @file{lion.xxx} as though it were
@file{lion.png}. For more on these, @pxref{\DeclareGraphicsRule}.

@table @code
@anchor{includegraphics type}
@item type
Specify the graphics type.

@anchor{includegraphics ext}
@item ext
Specify the graphics extension.
Only use this in conjunction with the option @code{type}.

@anchor{includegraphics read}
@item read
Specify the file extension of the read file.
Only use this in conjunction with the option @code{type}.

@anchor{includegraphics command}
@item command
Specify a command to be applied to this file.  Only use this in
conjunction with the option @code{type}.  @xref{Command line options}
for a discussion of enabling the @code{\write18} functionality to run
external commands.

@end table


@node \rotatebox
@subsection @code{\rotatebox}

@cindex rotation
@cindex rotating graphics
@cindex rotating text
@findex \rotatebox

Synopsis if you use the @file{graphics} package:

@example
\rotatebox@{@var{angle}@}@{@var{material}@}
@end example

Synopses if you use the @file{graphicx} package:

@example
\rotatebox@{@var{angle}@}@{@var{material}@}
\rotatebox[@var{key-value list}]@{@var{angle}@}@{@var{material}@}
@end example

Put @var{material} in a box and rotate it @var{angle} degrees
counterclockwise.

This example rotates the table column heads forty five degrees.

@example
\begin@{tabular@}@{ll@}
  \rotatebox@{45@}@{Character@} &\rotatebox@{45@}@{NATO phonetic@}   \\
  A                         &AL-FAH  \\
  B                         &BRAH-VOH
\end@{tabular@}
@end example

The @var{material} can be anything that goes in a box, including a graphic.

@example
  \rotatebox[origin=c]@{45@}@{\includegraphics[width=1in]@{lion@}@}
@end example

To place the rotated material, the first step is that @LaTeX{} sets
@var{material} in a box, with a reference point on the left baseline.
The second step is the rotation, by default about the reference point.
The third step is that @LaTeX{} computes a box to bound the rotated
material.  Fourth, @LaTeX{} moves this box horizontally so that the left
edge of this new bounding box coincides with the left edge of the box
from the first step (they need not coincide vertically).  This new
bounding box, in its new position, is what @LaTeX{} uses as the box when
typesetting this material.

If you use the @file{graphics} package then the rotation is about the
reference point of the box. If you use the @file{graphicx} package
then these are the options that can go in the @var{key-value list},
but note that you can get the same effect without needing this
package, except for the @code{x} and @code{y} options
(@pxref{\includegraphics}).

@table @code
@item origin
The point of the @var{material}'s box about which the rotation happens.
Possible value is any string containing one or two of: @code{l} for
left, @code{r} for right, @code{b} for bottom, @code{c} for center,
@code{t} for top, and @code{B} for baseline.  Thus, the first line here

@example
\rotatebox[origin=c]@{180@}@{moon@}
\rotatebox[origin=lB]@{180@}@{LeBateau@}
@end example

@noindent
will turn the picture upside down from the center while the second will
turn its picture upside down about its left baseline.  (The character
@code{c} gives the horizontal center in @code{bc} or @code{tc} but gives
the vertical center in @code{lc} or @code{rc}, and gives both in
@code{c}.)  The default is @code{lB}.

@item x, y
Specify an arbitrary point of rotation with
@code{\rotatebox[x=@var{@TeX{} dimension},y=@var{@TeX{}
dimension}]@{...@}} (@pxref{Units of length}).  These give the offset
from the box's reference point.

@item units
This key allows you to change the default of degrees counterclockwise.
Setting @code{units=-360} changes the direction to degrees clockwise and
setting @code{units=6.283185} changes to radians counterclockwise.

@end table


@node \scalebox
@subsection @code{\scalebox}

@cindex graphics, scaling
@cindex graphics, resizing
@cindex scaling
@cindex resizing
@cindex text, scaling
@cindex text, resizing
@findex \scalebox
@findex \reflectbox

Synopses:

@example
\scalebox@{@var{horizontal factor}@}@{@var{material}@}
\scalebox@{@var{horizontal factor}@}[@var{vertical factor}]@{@var{material}@}
\reflectbox@{@var{material}@}
@end example

Scale the @var{material}.

This example halves the size, both horizontally and vertically, of the
first text and doubles the size of the second.

@example
\scalebox@{0.5@}@{DRINK ME@} and \scalebox@{2.0@}@{Eat Me@}
@end example

If you do not specify the optional @var{vertical factor} then it
defaults to the same value as the @var{horizontal factor}.

You can use this command to resize a graphic, as here.

@example
\scalebox@{0.5@}@{\includegraphics@{lion@}@}
@end example

@noindent
If you use the @file{graphicx} package then you can accomplish the same
thing with optional arguments to @code{\includegraphics}
(@pxref{\includegraphics}).

The @code{\reflectbox} command abbreviates
@code{\scalebox@{-1@}[1]@{@var{material}@}}.  Thus, @code{Able was
I\reflectbox@{Able was I@}} will show the phrase @samp{Able was I}
immediately followed by its mirror reflection.


@node \resizebox
@subsection @code{\resizebox}

@cindex graphics, scaling
@cindex graphics, resizing
@cindex scaling
@cindex resizing
@cindex text, scaling
@cindex text, resizing
@findex \resizebox

Synopses:

@example
\resizebox@{@var{horizontal length}@}@{@var{vertical length}@}@{@var{material}@}
\resizebox*@{@var{horizontal length}@}@{@var{vertical length}@}@{@var{material}@}
@end example

Given a size, such as @code{3cm}, transform @var{material} to make it
that size.  If either @var{horizontal length} or @var{vertical length}
is an exclamation point@tie{}@code{!}  then the other argument is used
to determine a scale factor for both directions.

This example makes the graphic be a half inch wide and scales it
vertically by the same factor to keep it from being distorted.

@example
\resizebox@{0.5in@}@{!@}@{\includegraphics@{lion@}@}
@end example

The unstarred form @code{\resizebox} takes @var{vertical length} to be
the box's height while the starred form @code{\resizebox*} takes it to
be height+depth.  For instance, make the text have a height+depth of a
quarter inch with @code{\resizebox*@{!@}@{0.25in@}@{\parbox@{1in@}@{This
box has both height and depth.@}@}}.

You can use @code{\depth}, @code{\height}, @code{\totalheight}, and
@code{\width} to refer to the original size of the box.  Thus, make the
text two inches wide but keep the original height with
@code{\resizebox@{2in@}@{\height@}@{Two inches@}}.


@node Special insertions
@chapter Special insertions

@cindex special insertions
@cindex insertions of special characters

@LaTeX{} provides commands for inserting characters that have a
special meaning do not correspond to simple characters you can type.

@menu
* Reserved characters::         Inserting @samp{# $ % & @{ @} _ ~ ^ \}
* Upper and lower case::        Make text upper or lower case.
* Symbols by font position::    Inserting font symbols by number.
* Text symbols::                Inserting other non-letter symbols in text.
* Accents::                     Inserting accents.
* Additional Latin letters::    Inserting other non-English characters.
* \rule::                       Inserting lines and rectangles.
* \today::                      Inserting today's date.
@end menu


@node Reserved characters
@section Reserved characters

@cindex reserved characters
@cindex characters, reserved
@cindex special characters
@cindex characters, special
@LaTeX{} sets aside the following characters for special purposes. For
example, the percent sign@tie{}@code{%} is for comments.  They are
called @dfn{reserved characters} or @dfn{special characters}.

@example
# $ % & @{ @} _ ~ ^ \ 
@end example

@findex \#
@findex \$
@findex \%
@findex \&
@findex \_
@findex \@{
@findex \@}
If you want a reserved character to be printed as itself, in the text
body font, for all but the final three characters in that list simply
put a backslash@tie{}@code{\} in front of the character.  Thus,
typing @code{\$1.23} will produce@tie{}@code{$1.23} in your output.

@findex \~
@findex \^ 
@findex \textbackslash
As to the last three characters, to get a tilde in the text body font
use @code{\~@{@}} (omitting the curly braces would result in the next
character receiving a tilde accent).  Similarly, to get a get a text
body font circumflex use @code{\^@{@}}.  To get a backslash in the font
of the text body, enter @code{\textbackslash@{@}}.

To produce the reserved characters in a typewriter font use
@code{\verb!!} as below (the double backslash@tie{}@code{\\} is only
there to split the lines).

@example
\begin@{center@}
  \# \$ \% \& \@{ \@} \_ \~@{@} \^@{@} \textbackslash \\
  \verb!# $ % & @{ @} _ ~ ^ \!
\end@{center@}
@end example


@node Upper and lower case
@section Upper and lower case

@cindex uppercase
@cindex lowercase
@cindex characters, case of

Synopsis:

@example
\uppercase@{@var{text}@}
\lowercase@{@var{text}@}
\MakeUppercase@{@var{text}@}
\MakeLowercase@{@var{text}@}
@end example

Change the case of characters.  The @TeX{} primitives commands
@code{\uppercase} and @code{\lowercase} only work for American
characters. The @LaTeX{} commands @code{\MakeUppercase} and
@code{\MakeLowercase} commands also change characters accessed by
commands such as @code{\ae} or @code{\aa}.  The commands
@code{\MakeUppercase} and @code{\MakeLowercase} are robust but they have
moving arguments (@pxref{\protect}).

These commands do not change the case of letters used in the name of a
command within @var{text}.  But they do change the case of every other
Latin letter inside the argument @var{text}.  Thus,
@code{\MakeUppercase@{Let $y=f(x)$}@} produces @samp{LET Y=F(X)}.  Another
example is that the name of an environment will be changed, so that
@code{\MakeUppercase@{\begin@{tabular@} ... \end@{tabular@}@}} will
produce an error because the first half is changed to
@code{\begin@{TABULAR@}}.

@LaTeX{} uses the same fixed table for changing case throughout a
document, The table used is designed for the font encoding T1; this
works well with the standard @TeX{} fonts for all Latin alphabets but
will cause problems when using other alphabets.

To change the case of text that results from a macro inside @var{text}
you need to do expansion.  Here the @code{\Schoolname} produces
@samp{COLLEGE OF MATHEMATICS}.

@example
\newcommand@{\schoolname@}@{College of Mathematics@}
\newcommand@{\Schoolname@}@{\expandafter\MakeUppercase
@w{                           }\expandafter@{\schoolname@}@}
@end example

@PkgIndex{textcase}
The @file{textcase} package brings some of the missing feature of the
standard @LaTeX{} commands @code{\MakeUppercase} and
@code{\MakeLowerCase}.

@PkgIndex{mfirstuc} 
To uppercase only the first letter of words, you can use the package
@file{mfirstuc}.


@node Symbols by font position
@section Symbols by font position

@findex \symbol
@cindex accessing any character of a font
@cindex font symbols, by number

You can access any character of the current font using its number with
the @code{\symbol} command. For example, the visible space character
used in the @code{\verb*} command has the code decimal 32, so it can be
typed as @code{\symbol@{32@}}.

You can also specify numbers in octal (base 8) by using a @code{'}
prefix, or hexadecimal (base 16) with a @code{"} prefix, so the previous
example could also be written as @code{\symbol@{'40@}} or
@code{\symbol@{"20@}}.


@node Text symbols
@section Text symbols

@cindex text symbols
@cindex symbols, text

@findex textcomp @r{package}
@LaTeX{} provides commands to generate a number of non-letter symbols in
running text.  Some of these, especially the more obscure ones, are not
available in OT1. Unless you are using Xe@LaTeX{} or Lua@LaTeX{} then
you may need to load the @code{textcomp} package.

@ftable @code
@item \copyright
@itemx \textcopyright
@cindex copyright symbol
@copyright{} The copyright symbol.

@item \dag
@cindex dagger, in text
@BES{2020,@math{\dag}} The dagger symbol (in text).

@item \ddag
@cindex double dagger, in text
@BES{2021,@math{\ddag}} The double dagger symbol (in text).

@item \LaTeX
@cindex @LaTeX{} logo
@cindex logo, @LaTeX{}
The @LaTeX{} logo.

@item \LaTeXe
@cindex @LaTeX{}2e logo
@cindex logo, @LaTeX{}2e
The @LaTeX{}2e logo.

@item \guillemotleft @r{(@guillemotleft{})}
@itemx \guillemotright @r{(@guillemotright{})}
@itemx \guilsinglleft @r{(@guilsinglleft{})}
@itemx \guilsinglright @r{(@guilsinglright{})}
@cindex double guillemets
@cindex single guillemets
@cindex left angle quotation marks
@cindex right angle quotation marks
@cindex double angle quotation marks
@cindex single angle quotation marks
@cindex French quotation marks
@cindex quotation marks, French
@guillemotleft{}, @guillemotright{}, @guilsinglleft{}, @guilsinglright{}
Double and single angle quotation marks, commonly used in French.

@item \ldots
@itemx \dots
@itemx \textellipsis
@cindex ellipsis
@dots{}  An ellipsis (three dots at the baseline):  @code{\ldots}
and @code{\dots} also work in math mode.

@item \lq
@cindex left quote
@cindex opening quote
` Left (opening) quote.

@item \P
@itemx \textparagraph
@cindex paragraph symbol
@cindex pilcrow
@BES{00B6,\P} Paragraph sign (pilcrow).

@item \pounds
@itemx \textsterling
@cindex pounds symbol
@cindex sterling symbol
@pounds{} English pounds sterling.

@item \quotedblbase @r{(@quotedblbase{})}
@itemx \quotesinglbase @r{(@quotesinglbase{})}
@cindex double low-9 quotation mark
@cindex single low-9 quotation mark
@cindex low-9 quotation marks, single and double
@quotedblbase{} and @quotesinglbase{}
Double and single quotation marks on the baseline.

@item \rq
@cindex right quote
@cindex closing quote
' Right (closing) quote.

@item \S
@itemx \textsection
@cindex section symbol
@BES{00A7,\S} Section sign.

@item \TeX
@cindex @TeX{} logo
@cindex logo, @TeX{}
The @TeX{} logo.

@item \textasciicircum
@cindex circumflex, ASCII, in text
@cindex ASCII circumflex, in text
^ ASCII circumflex.

@item \textasciitilde
@cindex tilde, ASCII, in text
@cindex ASCII tilde, in text
~ ASCII tilde.

@item \textasteriskcentered
@cindex asterisk, centered, in text
@cindex centered asterisk, in text
* Centered asterisk.

@item \textbackslash
@cindex backslash, in text
\ Backslash.

@item \textbar
@cindex vertical bar, in text
@cindex bar, vertical, in text
| Vertical bar.

@item \textbardbl
@cindex vertical bar, double, in text
@cindex bar, double vertical, in text
@cindex double vertical bar, in text
@BES{23F8,||} Double vertical bar.

@item \textbigcircle
@cindex big circle symbols, in text
@cindex circle symbol, big, in text
@BES{25EF,} Big circle symbol.

@item \textbraceleft
@cindex left brace, in text
@cindex brace, left, in text
@{ Left brace.

@item \textbraceright
@cindex right brace, in text
@cindex brace, right, in text
@} Right brace.

@item \textbullet
@cindex bullet, in text
@bullet{} Bullet.

@item \textcircled@{@var{letter}@}
@cindex circled letter, in text
@BES{24B6,} Circle around @var{letter}.

@item \textcompwordmark
@itemx \textcapitalcompwordmark
@itemx \textascendercompwordmark
@cindex composite word mark, in text
@cindex cap height
@cindex ascender height
Used to separate letters that would normally ligature. For example,
@code{f\textcompwordmark i} produces @samp{fi} without a ligature. This
is most useful in non-English languages.  The
@code{\textcapitalcompwordmark} form has the cap height of the font
while the @code{\textascendercompwordmark} form has the ascender height.

@item \textdagger
@cindex dagger, in text
@BES{2020,@math{\dag}} Dagger.

@item \textdaggerdbl
@cindex dagger, double, in text
@cindex double dagger, in text
@BES{2021,@math{\ddag}} Double dagger.

@item \textdollar @r{(or @code{\$})}
@cindex dollar sign
@cindex currency, dollar
$ Dollar sign.

@item \textemdash @r{(or @code{---})}
@cindex em-dash
--- Em-dash (used for punctuation, as in
@code{The playoffs --- if you are fortunate enough to make the playoffs ---
is more like a sprint.}).

@item \textendash @r{(or @code{--})}
@cindex e-dash
-- En-dash (used for ranges, as in @code{See pages 12--14}).

@item \texteuro
@cindex euro symbol
@cindex currency, euro
@PkgIndex{eurosym}
The Euro symbol: @euro{}. For an alternative glyph design, try the
@file{eurosym} package; also, most fonts nowadays come with their own
Euro symbol (Unicode U+20AC).

@item \textexclamdown @r{(or @code{!`})}
@cindex exclamation point, upside-down
@exclamdown{} Upside down exclamation point.

@item \textgreater
@cindex greater than symbol, in text
> Greater than symbol.

@item \textless
@cindex less than symbol, in text
< Less than symbol.

@item \textleftarrow
@cindex arrow, left, in text
@cindex left arrow, in text
@BES{2190,} Left arrow.   

@item \textordfeminine
@itemx \textordmasculine
@cindex feminine ordinal symbol
@cindex masculine ordinal symbol
@cindex ordinals, feminine and masculine
@cindex Spanish ordinals, feminine and masculine
@ordf{}, @ordm{} Feminine and masculine ordinal symbols.

@item \textperiodcentered
@cindex period, centered, in text
@cindex centered period, in text
@BES{00B7,\cdot} Centered period.

@item \textquestiondown @r{(or @code{?`})}
@cindex question mark, upside-down
@questiondown{} Upside down question mark.

@item \textquotedblleft @r{(or @code{``})}
@cindex left quote, double
@cindex double left quote
`` Double left quote.

@item \textquotedblright @r{(or @code{''})}
@cindex right quote, double
@cindex double right quote
'' Double right quote.

@item \textquoteleft @r{(or @code{`})}
@cindex left quote, single
@cindex single left quote
` Single left quote.

@item \textquoteright @r{(or @code{'})}
@cindex right quote, single
@cindex single right quote
' Single right quote.

@item \textquotesingle
@cindex quote, single straight
@cindex straight single quote
@cindex single quote, straight
@BES{0027,} Straight single quote.  (From TS1 encoding.)  

@item \textquotestraightbase
@itemx \textquotestraightdblbase
@cindex quote, straight base
@cindex straight quote, base
@cindex double quote, straight base
@cindex straight double quote, base
@c Unicode doesn't have these https://en.wikipedia.org/wiki/Quotation_mark
Single and double straight quotes on the baseline.

@item \textregistered
@cindex registered symbol
@registeredsymbol{} Registered symbol.

@item \textrightarrow
@cindex arrow, right, in text
@cindex right arrow, in text
@BES{2192,} Right arrow.  

@item \textthreequartersemdash
@cindex three-quarters em-dash
@cindex em-dash, three-quarters
@BES{FE58,} ``Three-quarters'' em-dash, between en-dash and em-dash.

@item \texttrademark
@cindex trademark symbol
@BES{2122,^{\hbox{TM}}} Trademark symbol.

@c ?? Diff from \textthreequartersemdash?  In Unicode?
@item \texttwelveudash
@cindex two-thirds em-dash
@cindex em-dash, two-thirds
@BES{FE58,} ``Two-thirds'' em-dash, between en-dash and em-dash.   

@item \textunderscore
@cindex underscore, in text
_ Underscore.

@item \textvisiblespace
@cindex visible space symbol, in text
@BES{2423,} Visible space symbol.  

@end ftable


@node Accents
@section Accents

@cindex accents
@cindex characters, accented
@cindex letters, accented

@PkgIndex{babel}
@PkgIndex{polyglossia}
@cindex multilingual support
@LaTeX{} has wide support for many of the world's scripts and languages,
through the @code{babel} package and related support if you are using
pdf@LaTeX{}, or @file{polyglossia} if you are using Xe@LaTeX{} or
Lua@LaTeX{}.  This section does not cover that support. It only lists
the core @LaTeX{} commands for creating accented characters.  The
@code{\capital...} commands shown here produce alternative forms for use
with capital letters.  These are not available with OT1.

Below, to make them easier to find, the accents are all illustrated with
lowercase @samp{o}.

@findex \i @r{(dotless i)}
@cindex dotless i
Note that @code{\i} produces a dotless i,
@c @dotless{i},
@findex \j @r{(dotless j)}
@cindex dotless j
and @code{\j} produces a dotless j.
@c @dotless{j}.
These are often used in place of their dotted counterparts when they are
accented.

@table @code
@item \"
@itemx \capitaldieresis
@findex \" @r{(umlaut accent)}
@findex \capitaldieresis
@cindex umlaut accent
@cindex dieresis accent
@"{o} Umlaut (dieresis).

@item \'
@itemx \capitalacute
@findex \' @r{(acute accent)}
@findex \capitalacute
@cindex acute accent
@'{o} Acute accent.

@item \.
@findex \. @r{(dot-over accent)}
@cindex dot accent
@cindex dot-over accent
@dotaccent{o}  Dot accent.

@item \=
@itemx \capitalmacron
@findex \= @r{(macron accent)}
@findex \capitalmacron
@cindex macron accent
@cindex overbar accent
@cindex bar-over accent
@={o} Macron (overbar) accent.

@item \^
@itemx \capitalcircumflex
@findex \^ @r{(circumflex accent)}
@findex \capitalcircumflex
@cindex circumflex accent
@cindex hat accent
@^{o} Circumflex (hat) accent.

@item \`
@itemx \capitalgrave
@findex \` @r{(grave accent)}
@findex \capitalgrave
@cindex grave accent
@`{o} Grave accent.

@item \~
@itemx \capitaltilde
@findex \~ @r{(tilde accent)}
@findex \capitaltilde
@cindex tilde accent
@~{n} Tilde accent.

@item \b
@findex \b @r{(bar-under accent)}
@cindex bar-under accent
@ubaraccent{o} Bar accent underneath.

@findex \underbar
@cindex underbar
Related to this, @code{\underbar@{@var{text}@}} produces a bar under
@var{text}.  The argument is always processed in LR mode
(@pxref{Modes}).  The bar is always a fixed position under the baseline,
thus crossing through descenders.  See also @code{\underline} in
@ref{Math miscellany}.

@item \c
@itemx \capitalcedilla
@findex \c @r{(cedilla accent)}
@findex \capitalcedilla
@cindex cedilla accent
@,{c} Cedilla accent underneath.

@item \d
@itemx \capitaldotaccent
@findex \d @r{(dot-under accent)}
@findex \capitaldotaccent
@cindex dot-under accent
@udotaccent{o} Dot accent underneath.

@item \H
@itemx \capitalhungarumlaut
@findex \H @r{(Hungarian umlaut accent)}
@findex \capitalhungarumlaut
@cindex hungarian umlaut accent
@H{o} Long Hungarian umlaut accent.

@item \k
@itemx \capitalogonek
@findex \k @r{(ogonek)}
@findex \capitalogonek
@cindex ogonek
@ogonek{o} Ogonek.  Not available in the OT1 encoding.

@item \r
@itemx \capitalring
@findex \r @r{(ring accent)}
@findex \capitalring
@cindex ring accent
@ringaccent{o} Ring accent.

@item \t
@itemx \capitaltie
@itemx \newtie
@itemx \capitalnewtie
@findex \t @r{(tie-after accent)}
@findex \capitaltie
@findex \newtie
@findex \capitalnewtie
@cindex tie-after accent
@tieaccent{oo} Tie-after accent.  The @code{\newtie} form is centered in
its box.

@item \u
@itemx \capitalbreve
@findex \u @r{(breve accent)}
@findex \capitalbreve
@cindex breve accent
@u{o} Breve accent.

@item \v
@itemx \capitalcaron
@findex \v @r{(breve accent)}
@findex \capitalcaron
@cindex hacek accent
@cindex check accent
@cindex caron accent
@v{o}  H@'a@v{c}ek (check, caron) accent.

@end table


@node Additional Latin letters
@section Additional Latin letters

@anchor{Non-English characters}
@cindex Latin letters, additional
@cindex letters, additional Latin
@cindex extended Latin 
@cindex special characters
@cindex non-English characters
@cindex characters, non-English

Here are the basic @LaTeX{} commands for inserting letters beyond
A--Z that extend the Latin alphabet, used primarily in languages other
than English.

@table @code
@item \aa
@itemx \AA
@findex \aa (@aa{})
@findex \AA (@AA{})
@cindex aring
@aa{} and @AA{}.

@item \ae
@itemx \AE
@findex \ae (@ae{})
@findex \AE (@AE{})
@cindex ae ligature
@ae{} and @AE{}.

@item \dh
@itemx \DH
@findex \dh (@dh{})
@findex \DH (@DH{})
@cindex Icelandic eth
@cindex eth, Icelandic letter
Icelandic letter eth: @dh{} and @DH{}. Not available with @sc{OT1}
encoding, you need the @file{fontenc} package to select an alternate
font encoding, such as @sc{T1}.

@item \dj
@itemx \DJ
@findex \dj
@findex \DJ
Crossed d and D, a.k.a.@: capital and small letter d with stroke.  Not
available with @sc{OT1} encoding, you need the @file{fontenc} package to
select an alternate font encoding, such as @sc{T1}.

@item \ij
@itemx \IJ
@findex \ij (ij)
@findex \IJ (IJ)
@cindex ij letter, Dutch
ij and IJ (except somewhat closer together than appears here).

@item \l
@itemx \L
@findex \l (@l{})
@findex \L (@L{})
@cindex polish l
@l{} and @L{}.

@item \ng
@itemx \NG
@findex \ng
@findex \NG
Lappish letter eng, also used in phonetics.

@item \o
@itemx \O
@findex \o (@o{})
@findex \O (@O{})
@cindex oslash
@o{} and @O{}.

@item \oe
@itemx \OE
@findex \oe (@oe{})
@findex \OE (@OE{})
@cindex oe ligature
@oe{} and @OE{}.

@item \ss
@itemx \SS
@findex \ss (@ss{})
@findex \SS (SS)
@cindex es-zet German letter
@cindex sharp S letters
@ss{} and SS.

@item \th
@itemx \TH
@findex \th (@th{})
@findex \TH (@TH{})
@cindex Icelandic thorn
@cindex thorn, Icelandic letter
Icelandic letter thorn: @th{} and @TH{}. Not available with @sc{OT1}
encoding, you need the @file{fontenc} package to select an alternate
font encoding, such as @sc{T1}.

@end table


@node \rule
@section @code{\rule}

@findex \rule

Synopsis, one of:

@example
\rule@{@var{width}@}@{@var{thickness}@}
\rule[@var{raise}]@{@var{width}@}@{@var{thickness}@}
@end example

Produce a @dfn{rule}, a filled-in rectangle.

@cindex Halmos symbol
@cindex tombstone
This produces a rectangular blob, sometimes called a Halmos symbol,
often used to mark the end of a proof.

@example
\newcommand@{\qedsymbol@}@{\rule@{0.4em@}@{2ex@}@}
@end example

@PkgIndex{amsthm}
@noindent
The @file{amsthm} package includes this command, with a somewhat
different-looking symbol.

The mandatory arguments give the horizontal @var{width} and vertical
@var{thickness} of the rectangle.  They are rigid lengths
(@pxref{Lengths}).  The optional argument @var{raise} is also a rigid
length, and tells @LaTeX{} how much to raise the rule above the
baseline, or lower it if the length is negative.

This produces a line, a rectangle that is wide but not tall.

@example
\noindent\rule@{\textwidth@}@{0.4pt@}
@end example

@noindent
The line is the width of the page and 0.4@tie{}points tall.  This line
thickness is common in @LaTeX{}.

A rule that has zero width, or zero thickness, will not show up in the
output, but can cause @LaTeX{} to change the output around it.
@xref{\strut} for examples.


@node \today
@section @code{\today}

@findex \today
@cindex date, today's
@cindex today's date

Synopsis:

@example
\today
@end example

Produce today's date in the format @samp{@var{month} @var{dd},
@var{yyyy}}.  An example of a date in that format is @samp{July 4,
1976}.

@PkgIndex{babel}
@PkgIndex{polyglossia}
Multilingual packages such as @file{babel} or @file{polyglossia}, or
classes such as @file{lettre}, will localize @code{\today}. For example,
the following will output @samp{4 juillet 1976}:

@example
\year=1976 \month=7 \day=4
\documentclass@{minimal@}
\usepackage[french]@{babel@}
\begin@{document@}
\today
\end@{document@}
@end example

@noindent
@code{\today} uses the counters @code{\day}, @code{\month}, and
@code{\year} (@pxref{\day & \month & \year}).

@PkgIndex{datetime}
A number of package on CTAN work with dates.  One is @file{datetime} package
which can produce a wide variety of date formats, including ISO standards.

The date is not updated as the @LaTeX{} process runs, so in principle the
date could be incorrect by the time the program finishes.


@node Splitting the input
@chapter Splitting the input

@cindex splitting the input file
@cindex input file

@LaTeX{} lets you split a large document into several smaller ones.
This can simplify editing or allow multiple authors to work on the
document.  It can also speed processing.

Regardless of how many separate files you use, there is always one
@cindex root file
@cindex file, root
@dfn{root file}, on which @LaTeX{} compilation starts.  This shows such
a file with five included files.

@example
\documentclass@{book@}
\includeonly@{  % comment out lines below to omit compiling
  pref,
  chap1,
  chap2,
  append,
  bib
  @}
\begin@{document@}
\frontmatter
\include@{pref@} 
\mainmatter
\include@{chap1@} 
\include@{chap2@}
\appendix
\include@{append@}
\backmatter
\include@{bib@} 
\end@{document@}
@end example

@noindent
This will bring in material from @file{pref.tex}, @file{chap1.tex},
@file{chap2.tex}, @file{append.tex}, and @file{bib.tex}.  If you compile
this file, and then comment out all of the lines inside
@code{\includeonly@{...@}} except for @code{chap1,} and compile again,
then @LaTeX{} will only process the material in the first chapter.
Thus, your output will appear more quickly and be shorter to print.
However, the advantage of the @code{\includeonly} command is that
@LaTeX{} will retain the page numbers and all of the cross reference
information from the other parts of the document so these will appear in
your output correctly.

@xref{Larger book template} for another example of @code{\includeonly}.

@menu
* \endinput::                 Stop including material from a file.
* \include & \includeonly::   Conditionally include files.
* \input::                    Unconditionally include a file.
@end menu



@node \endinput
@section @code{\endinput}

@findex \endinput

Synopsis:

@example
\endinput
@end example

When you @code{\include@{filename@}}, inside @file{filename.tex} the
material after @code{\endinput} will not be included.  This command is
optional; if @file{filename.tex} has no @code{\endinput} then @LaTeX{}
will read all of the file.

For example, suppose that a document's root file has
@code{\input@{chap1@}} and this is @file{chap1.tex}.

@example
\chapter@{One@}
This material will appear in the document. 
\endinput
This will not appear.
@end example

This can be useful for putting documentation or comments at the end of a
file, or for avoiding junk characters that can be added during mailing.
It is also useful for debugging: one strategy to localize errors is to
put @code{\endinput} halfway through the included file and see if the
error disappears.  Now, knowing which half contains the error, moving
@code{\endinput} to halfway through that area further narrows down the
location. This process rapidly finds the offending line.

After reading @code{\endinput}, @LaTeX{} continues to read to the end of
the line, so something can follow this command and be read nonetheless.
This allows you, for instance, to close an @code{\if...} with a
@code{\fi}.


@node \include & \includeonly
@section @code{\include} & @code{\includeonly}

@findex \include
@findex \includeonly

Synopsis:

@example
\includeonly@{  % in document preamble
  ...
  @var{filename},
  ...
  @}
  ...
\include@{@var{filename}@}  % in document body 
@end example

Bring material from the external file @file{@var{filename}.tex} into a
@LaTeX{} document.

The @code{\include} command does three things: it executes
@code{\clearpage} (@pxref{\clearpage & \cleardoublepage}), then it
inputs the material from @file{@var{filename}.tex} into the document,
and then it does another @code{\clearpage}.  This command can only
appear in the document body.  The @code{\includeonly} command controls
which files will be read by @LaTeX{} under subsequent @code{\include}
commands.  Its list of filenames is comma-separated, and it can only
appear in the preamble.

This example root document, @file{constitution.tex}, brings in
three files, @file{preamble.tex}, @file{articles.tex}, and
@file{amendments.tex}.

@example
\documentclass@{book@}
\includeonly@{
  preamble,
  articles,
  amendments
  @}
\begin@{document@}
\include@{preamble@}
\include@{articles@}
\include@{amendments@}
\end@{document@}
@end example

@noindent
The file @file{preamble.tex} contains no special code; you have just
excerpted the chapter from @file{consitution.tex} and put it in a
separate file just for editing convenience.

@example
\chapter@{Preamble@}
We the People of the United States,
in Order to form a more perfect Union, ...
@end example

@noindent
Running @LaTeX{} on @file{constitution.tex} makes the material from the
three files appear in the document but also generates the auxiliary
files @file{preamble.aux}, @file{articles.aux}, and
@file{amendments.tex}. These contain information such as page numbers
and cross-references (@pxref{Cross references}).  If you now comment out
@code{\includeonly}'s lines with @code{preamble} and @code{amendments}
and run @LaTeX{} again then the resulting document shows only the
material from @file{articles.tex}, not the material from
@file{preamble.tex} or @file{amendments.tex}.  Nonetheless, all of the
auxiliary information from the omitted files is still there, including
the starting page number of the chapter.

If the document preamble does not have @code{\includeonly} then
@LaTeX{} will include all the files you call for with @code{\include}
commands.

The @code{\include} command makes a new page.  To avoid that, see
@ref{\input} (which, however, does not retain the auxiliary
information).

@xref{Larger book template} for another example using @code{\include}
and @code{\includeonly}.  That example also uses @code{\input} for some
material that will not necessarily start on a new page.

File names can involve paths.

@example
\documentclass@{book@}
\includeonly@{
  chapters/chap1,
  @}
\begin@{document@}
\include@{chapters/chap1@}
\end@{document@}
@end example

To make your document portable across distributions and platforms you
should avoid spaces in the file names. The tradition is to instead use
dashes or underscores.  Nevertheless, for the name @samp{amo amas amat},
this works under @TeX{} Live on GNU/Linux:

@example
\documentclass@{book@}
\includeonly@{
  "amo\space amas\space amat"
  @}
\begin@{document@}
\include@{"amo\space amas\space amat"@}
\end@{document@}
@end example

and this works under MiK@TeX{} on Windows:

@example
\documentclass@{book@}
\includeonly@{
  @{"amo amas amat"@}
  @}
\begin@{document@}
\include@{@{"amo amas amat"@}@}
\end@{document@}
@end example

@cindex nested @code{\include}, not allowed
You cannot use @code{\include} inside a file that is being included or
you get @samp{LaTeX Error: \include cannot be nested.}  The
@code{\include} command cannot appear in the document preamble; you will
get @samp{LaTeX Error: Missing \begin@{document@}}.

If a file that you @code{\include} does not exist, for instance if you
@code{\include@{athiesm@}} but you meant @code{\include@{atheism@}},
then @LaTeX{} does not give you an error but will warn you @samp{No file
athiesm.tex.}  (It will also create @file{athiesm.aux}.)

If you @code{\include} the root file in itself then you first get
@samp{LaTeX Error: Can be used only in preamble.}  Later runs get
@samp{TeX capacity exceeded, sorry [text input levels=15]}.  To fix
this, you must remove the inclusion @code{\include@{root@}} but also
delete the file @file{@var{root}.aux} and rerun @LaTeX{}.


@node \input
@section @code{\input}

@findex \input

Synopsis:

@example
\input@{@var{filename}@}
@end example

@LaTeX{} processes the file as if its contents were inserted in the
current file.  For a more sophisticated inclusion mechanism see
@ref{\include & \includeonly}.

If @var{filename} does not end in @samp{.tex} then @LaTeX{} first tries
the filename with that extension; this is the usual case.  If
@var{filename} ends with @samp{.tex} then @LaTeX{} looks for the
filename as it is.

For example, this

@example
\input@{macros@}
@end example

@noindent
will cause @LaTeX{} to first look for @file{macros.tex}. If it finds
that file then it processes its contents as thought they had been
copy-pasted in.  If there is no file of the name @file{macros.tex} then
@LaTeX{} tries the name @file{macros}, without an extension. (This may
vary by distribution.)

To make your document portable across distributions and platforms you
should avoid spaces in the file names. The tradition is to instead use
dashes or underscores.  Nevertheless, for the name @samp{amo amas amat},
this works under @TeX{} Live on GNU/Linux:

@example
\input@{"amo\space amas\space amat"@}
@end example

and this works under MiK@TeX{} on Windows:

@example
\input@{@{"amo amas amat"@}@}
@end example


@node Front/back matter
@chapter Front/back matter

@menu
* Table of contents etc.::  Table of contents, list of figures, list of tables.
* Indexes::                  Generate an index.
* Glossaries::               Generate a glossary.
@end menu


@node Table of contents etc.
@section Table of contents etc.

@cindex table of contents, creating

@findex \tableofcontents
@findex .toc @r{file}
@findex \listoffigures
@findex \listoftables
@findex .lof @r{file}
@findex .lot @r{file}

Synopsis, one of:

@example
\tableofcontents
\listoffigures
\listoftables
@end example

Produce a table of contents, or list of figures, or list of tables.  Put
the command in the input file where you want the table or list to
go. You do not type the entries; for example, typically the table of
contents entries are automatically generated from the sectioning
commands @code{\chapter}, etc.

This example illustrates the first command, @code{\tableofcontents}.
@LaTeX{} will produce a table of contents on the book's first page.

@example
\documentclass@{book@}
% \setcounter@{tocdepth@}@{1@}
\begin@{document@}
\tableofcontents\newpage
  ...
\chapter@{...@}
  ...
\section@{...@}
  ...
\subsection@{...@}
  ...
\end@{document@}
@end example

@noindent
Uncommenting the second line would cause that table to contain chapter
and section listings but not subsection listings, because the
@code{\section} command has level@tie{}1.  @xref{Sectioning} for level
numbers of the sectioning units.  For more on the @code{tocdepth}
@pxref{Sectioning/tocdepth}.

Another example of the use of @code{\tableofcontents} is in @ref{Larger
book template}.

If you want a page break after the table of contents, write a
@code{\newpage} command after the @code{\tableofcontents} command, as
above.

To make the table of contents @LaTeX{} stores the information in an
auxiliary file named @file{@var{root-file}.toc} (@pxref{Splitting the
input}).  For example, this @LaTeX{} file @file{test.tex}

@example
\documentclass@{article@}
\begin@{document@}
\tableofcontents\newpage
\section@{First section@}
\subsection@{First subsection@}
  ...
@end example

@noindent
writes the following line to @file{test.toc}.

@example
\contentsline @{section@}@{\numberline @{1@}First section@}@{2@}
\contentsline @{subsection@}@{\numberline @{1.1@}First subsection@}@{2@}
@end example

@noindent
The @code{section} or @code{subsection} is the sectioning unit.  The
hook @code{\numberline} lets you to change how the information appears
in the table of contents.  Of its two arguments, @code{1} or @code{1.1}
is the sectioning unit number and @code{First section} or @code{First
subsection} is the title.  Finally, @code{2} is the page number on which
the sectioning units start.

One consequence of this auxiliary file storage strategy is that to get the
contents page correct you must run @LaTeX{} twice, once to store the
information and once to get it.  In particular, the first time that you
run @LaTeX{} on a new document, the table of contents page will be empty
except for its @samp{Contents} header.  Just run it again.

The commands @code{\listoffigures} and @code{\listoftables} produce a
list of figures and a list of tables.  They work the same way as the
contents commands; for instance, these work with information stored in
@file{.lof} and @file{.lot} files.

@PkgIndex{babel}
@PkgIndex{polyglossia}
To change the header for the table of contents page do something like
the first line here.

@example
\renewcommand@{\contentsname@}@{Table of contents@}
\renewcommand@{\listfigurename@}@{Plots@}
\renewcommand@{\listtablename@}@{Tables@}
@end example

@noindent
Similarly, the other two lines will do the other two.
Internationalization packages such as @file{babel} or @file{polyglossia}
will change the headers depending on the chosen base language.

@PkgIndex{tocloft}
@PkgIndex{tocbibbind}
CTAN has many packages for the table of contents and lists of figures
and tables.  One convenient one for adjusting some aspects of the
default, such as spacing, is @file{tocloft}.  And, @file{tocbibbind}
will automatically add the bibliography, index, etc. to the table of
contents.

@menu
* \addcontentsline::    Add an entry to table of contents, etc.
* \addtocontents::      Add text directly to table of contents file, etc.
* \nofiles::            Prevent writing to auxiliary files.
@end menu


@node \addcontentsline
@subsection @code{\addcontentsline}

@findex \addcontentsline
@cindex table of contents entry, manually adding

Synopsis:

@example
\addcontentsline@{@var{ext}@}@{@var{unit}@}@{@var{text}@}
@end example

@findex \contentsline
Add an entry to the file specified by @var{ext}.  Usually @var{ext} is
one of @code{toc} for the table of contents, @code{lof} for the list of
figures, or @code{lot} for the list of tables.

The following will result in an @samp{Appendices} line in the table of
contents.

@example
\addcontentsline@{toc@}@{section@}@{\protect\textbf@{Appendices@}@}
@end example

@noindent
It will appear at the same indentation level as the sections, will be in
boldface, and will be assigned the page number associated with the point
where it appears in the input file.

The @code{\addcontentsline} command writes information to the file
@file{@var{root-name}.@var{ext}}.  It writes that information as the
text of the command
@code{\contentsline@{@var{unit}@}@{@var{text}@}@{@var{num}@}}, where
@code{@var{num}} is the current value of counter @code{@var{unit}}.  The
most common case is the table of contents and there @var{num} is the
page number of the first page of @var{unit}.

This command is invoked by the sectioning commands @code{\chapter},
etc., and also by @code{\caption} inside a float environment.  But it is
also used by authors.  For example, in a book to have the preface
unnumbered, you may use the starred @code{\chapter*}.  But that does not
put in table of contents information, so you can enter it manually, as
here.

@example
\chapter*@{Preface@}
\addcontentsline@{toc@}@{chapter@}@{\protect\numberline@{@}Preface@}
@end example

@noindent
In the @file{.toc} file @LaTeX{} will put the line @code{\contentsline
@{chapter@}@{\numberline @{@}Preface@}@{3@}}; note the page number
@samp{3}.

@c xx how hardwired are these values?  other unit names?

All of the arguments for @code{\addcontentsline} are required.

@table @var
@item ext
Typically one of the strings @code{toc} for the table of contents,
@code{lof} for the list of figures, or @code{lot} for the list of
tables. The filename extension of the information file.

@item unit
A string that depends on the value of the @var{ext} argument:

@table @code
@item toc
For the table of contents, this is the name of a sectional unit:
@code{part}, @code{chapter}, @code{section}, @code{subsection}, etc.

@item lof
For the list of figures: @code{figure}.

@item lot
For the list of tables: @code{table}.
@end table

@item text
The text of the entry.  You must @code{\protect} any commands that are
fragile (@pxref{\protect}).
@end table

The @code{\addcontentsline} command has an interaction with
@code{\include} (@pxref{\include & \includeonly}). If you use them at
the same level, as with
@code{\addcontentsline@{...@}@{...@}@{...@}\include@{...@}} then lines
in the table of contents can come out in the wrong order.  The solution
is to move @code{\addcontentsline} into the file being included.

If you use a @var{unit} that @LaTeX{} does not recognize, as here

@example
\addcontentsline@{toc@}@{setcion@}@{\protect\textbf@{Appendices@}@}
@end example

@noindent
then you don't get an error but the formatting in the table of contents
will not make sense.


@node \addtocontents
@subsection @code{\addtocontents}

@findex \addtocontents@{@var{ext}@}@{@var{text}@}

Synopsis:

@example
\addtocontents@{@var{ext}@}@{@var{text}@}
@end example

Add @var{text}, which may be text or formatting commands, directly to
the auxiliary file with extension @var{ext}.  This is most commonly used
for the table of contents so that is the discussion here, but this also
applies to the list of figures and list of tables.

This will put some vertical space in the table of contents after the
@samp{Contents} header.

@example
\tableofcontents\newpage
\addtocontents@{toc@}@{\protect\vspace*@{3ex@}@}
@end example

The @code{\addtocontents} command has two arguments.  Both are
required.

@table @var
@item ext
Typically one of: @file{toc} for the table of contents, @file{lof} for
the list of figures, or @file{lot} for the list of tables.  The
extension of the file holding the information.

@item text
The text, and possibly commands, to be written.
@end table

The sectioning commands such as @code{\chapter} use the
@code{\addcontentsline} command to store information.  This command
creates lines in the @file{.toc} auxiliary file containing the
@code{\contentsline} command (@pxref{\addcontentsline}).  In contrast,
the command @code{\addtocontents} puts material directly in that file.

The @code{\addtocontents} command has an interaction with
@code{\include} (@pxref{\include & \includeonly}). If you use them at
the same level, as with
@code{\addtocontents@{...@}@{...@}\include@{...@}} then lines in the
table of contents can come out in the wrong order.  The solution is to
move @code{\addtocontents} into the file being included.


@node \nofiles
@subsection @code{\nofiles}

@findex \nofiles

Synopsis:

@example
\nofiles
@end example

Prevent @LaTeX{} from writing any auxiliary files.  The only output will
be the @file{.log} and @file{.pdf} (or @file{.dvi}) files.  This command
must go in the preamble.

Because of the @code{\nofiles} command this example will not produce a
@file{.toc} file.

@example
\documentclass@{book@}
\nofiles
\begin@{document@}
\tableofcontents\newpage
\chapter@{...@}
  ...
@end example

@noindent
@LaTeX{} will not erase any existing auxiliary files, so if you insert
the @code{\nofiles} command after you have run the file and gotten
a @file{.toc} then the table of contents page will continue to show
the old information.


@node Indexes
@section Indexes

@cindex indexes

@findex \makeindex
@findex \index
@cindex @file{.idx} file

This document has an index.

@example
\documentclass@{article@}
\usepackage@{makeidx@} \makeindex
  ...
\begin@{document@}
  ...
Recall Wilson's Theorem: \index@{Wilson's Theorem@}
a number \( n>1 \) is prime if and only if the factorial of \( n-1 \)
is congruent to \( -1 \) modulo~\( n \).
  ...
\printindex
  ...
@end example

@noindent
The @code{\usepackage@{makeidx@}} and @code{\makeindex} in the preamble
bring in the relevant commands.

Producing an index is a three stage process.  First, in the document
body you declare index entries with the @code{\index} command
(@pxref{\index}).  When you run @LaTeX{}, the @code{\index} writes its
information to an auxiliary file @file{@var{root-name}.idx}.  Next, to
alphabetize and to do other manipulations you run an external command,
typically @command{makeindex} or @command{xindy} (@pxref{makeindex}).
These output a file @file{@var{root-name}.ind}.  Finally, you bring the
information back into your document and typeset it with the
@code{\printindex} command (@pxref{\printindex}).

@PkgIndex{showidx}
@PkgIndex{multind}
There are many packages that apply to indexing commands.  The
@code{showidx} package causes each index entries to be shown in the
margin on the page where the entry appears.  This can help in preparing
the index.  The @code{multind} package supports multiple indexes.  See
also the @TeX{} FAQ entry on this topic,
@url{http://www.tex.ac.uk/cgi-bin/texfaq2html?label=multind}.

@menu
* \index::        Declare an index entry.
* makeindex::     Alphabetize index entries.
* \printindex::   Put the index here.
@end menu


@node \index
@subsection @code{\index}

@cindex index entry
@findex \index

Synopsis:

@example
\index@{@var{index-entry-string}@}
@end example

Declare an entry in the index.  This command is fragile
(@pxref{\protect}).

For example, as described in @ref{Indexes}, one way to get an index from
what's below is to compile the document with @code{pdflatex test}, then
process the index entries with @code{makeindex test}, and then compile
again with @code{pdflatex test}.

@example
W~Ackermann (1896--1962).\index@{Ackermann@}
  ...
Ackermann function\index@{Ackermann!function@}
  ...
rate of growth\index@{Ackermann!function!growth rate@}
@end example

@noindent
All three index entries will get a page number, such as @samp{Ackermann,
22}.  @LaTeX{} will format the second as a subitem of the first, on the
line below it and indented, and the third as a subitem of the second.
Three levels deep is as far as you can nest subentries.  (If you add
@code{\index@{Ackermann!function!growth rate!comparison@}} then
@command{makeindex} says @samp{Scanning input file test.idx....done (4
entries accepted, 1 rejected)} and nothing appears in the index).

If you enter a second @code{\index} with the same
@var{index-entry-string} then you will get a single index entry with two
page numbers (unless they happen to fall on the same page).  Thus,
adding @code{as for Ackermann.\index@{Ackermann@}} later in the same
document as above will give an index entry like @samp{Ackermann, 22,
151}.  Also, you can enter the index entries in any order, so for
instance @code{\index@{Ackermann!function@}} could come before
@code{\index@{Ackermann@}}.

@cindex index, page range
Get a page range in the output, like @samp{Hilbert, 23--27}, as here.

@example
W~Ackermann (1896--1962).\index@{Ackermann@}
  ...
D~Hilbert (1862--1943)\index@{Ackermann!Hilbert\(@}
  ...
disapproved of his marriage.\index@{Ackermann!Hilbert\)@}
@end example

@noindent
If the beginning and ending of the page range are equal then the system
just gives a single page entry, not a range.

If you index subentries but not a main entry, as with
@code{\index@{Jones!program@}} and @code{\index@{Jones!results@}}, then
the output is the item @samp{Jones} with no comma or page number,
followed by two subitems, like @samp{program, 50} and @samp{results,
51}.

@cindex `see' and `see also' index entries
@cindex  index entries, `see' and `see also'
@findex \seename
@findex \alsoname
@PkgIndex{babel} @PkgIndex{polyglossia}

Generate a index entry that says @samp{See} by using a vertical bar
character: @code{\index@{Ackermann!function|see@{P\'eter's
function@}@}}.  You can instead get @samp{See also} with @code{seealso}.
(The text @samp{See} is defined by @code{\seename}, and @samp{See also}
by @code{\alsoname}.  You can redefine these either by using an
internationalization package such as @file{babel} or @file{polyglossia},
or directly as with @code{\renewcommand@{\alsoname@}[1]@{Also see
#1@}}.)

The @samp{See} feature is part of a more general functionality.  After
the vertical bar you can put the name of a one-input command, as in
@code{\index@{group|textit@}} (note the missing backslash on the
@code{\textit} command) and the system will apply that command to the
page number, here giving something like @code{\textit@{7@}}.  You can
define your own one-input commands, such as
@code{\newcommand@{\definedpage@}[1]@{@{\color@{blue@}#1@}@}} and then
@code{\index@{Ackermann!function|definedpage@}} will give a blue page
number (@pxref{Color}).  Another, less practical, example is this,

@c credit Ian Thompson https://tex.stackexchange.com/a/272572/121234
@example
\newcommand\indexownpage[1]@{#1, \thepage@}
  ... Epimenides.\index@{self-reference|indexownpage@}
@end example

@noindent
which creates an entry citing the page number of its own index listing.

The two functions just described combine, as here

@example
\index@{Ackermann!function|(definedpage@}
  ...
\index@{Ackermann!function|)@}
@end example

@noindent
which outputs an index entry like @samp{function, 23--27} where the page
number range is in blue.

Consider an index entry such as @samp{@BES{03B1,\alpha}-ring}.  Entering
it as @code{$\alpha$-ring} will cause it to be alphabetized according to
the dollar sign. You can instead enter it using an at-sign, as
@code{\index@{alpha-ring@@$\alpha$-ring@}}.  If you specify an entry
with an at-sign separating two strings, @code{@var{pos}@@@var{text}},
then @var{pos} gives the alphabetical position of the entry while
@var{text} produces the text of the entry.  Another example is that
@code{\index@{Saint Michael's College@@SMC@}} produces an index entry
@samp{SMC} alphabetized into a different location than its spelling
would naturally give it.

To put a @code{!}, or @code{@@}, or @code{|} character in an index
entry, preceding it with a double quote, @code{"}.  (The double quote
gets deleted before alphabetization.)

@PkgIndex{index}
A number of packages on CTAN have additional functionality beyond that
provided by @file{makeidx}.  One is @file{index}, which allows for
multiple indices and contains a command
@code{\index*@{@var{index-entry-string}@}} that prints the
@var{index-entry-string} as well as indexing it.

@findex \indexentry
@cindex idx file
The @code{\index} command writes the indexing information to the file
@file{@var{root-name}.idx} file.  Specifically, it writes text of the
command
@code{\indexentry@{@var{index-entry-string}@}@{@var{page-num}@}},
where @var{page-num} is the value of the @code{\thepage} counter.  On
occasion, when the @code{\printindex} command is confused, you have to
delete this file to start with a fresh slate.

If you omit the closing brace of an @code{\index} command then you get a
message like this.

@example
Runaway argument?  @{Ackermann!function
!  Paragraph ended before \@@wrindex was complete.
@end example


@node makeindex
@subsection @command{makeindex}

@cindex index, processing
@findex makeindex
@cindex @command{makeindex} program
@cindex @file{.ind} file
@cindex @file{.idx} file

Synopsis, one of:

@example
makeindex @var{filename}
makeindex -s @var{style-file} @var{filename}
makeindex @var{options} @var{filename0} ...
@end example

Sort, and otherwise process, the index information in the auxiliary file
@var{filename}.  This is a command line program.  It takes one or more
raw index files, @file{@var{filename}.idx} files, and produces the
actual index file, the @file{@var{filename}.ind} file that is input by
@code{\printindex} (@pxref{\printindex}).

@cindex @file{.isty} file
@findex index, style file
@findex makeindex, style file
The first form of the command suffices for many uses.  The second allows
you to format the index by using an @dfn{index style file}, a
@file{.isty} file.  The third form is the most general; see the full
documentation on CTAN.

This is a simple @file{.isty} file.

@example
% book.isty 
%   $ makeindex -s book.isty -p odd book.idx
% creates the index as book.ind, starting on an odd page. 
preamble
"\\pagestyle@{empty@}
\\small
\\begin@{theindex@}
\\thispagestyle@{empty@}"

postamble
"\n
\\end@{theindex@}"
@end example

The description here covers only some of the index formatting
possibilities in @var{style-file}. For a full list see the documentation
on CTAN.

A style file consists of a list of pairs: @var{specifier} and
@var{attribute}.  These can appear in the file in any order.  All of the
@var{attributes} are strings, except where noted.  Strings are
surrounded with double quotes, @code{"}, and the maximum length of a
string is 144 characters.  The @code{\n} is for a newline and @code{\t}
is for a tab.  Backslashes are escaped with another backslash,
@code{\\}.  If a line begins with a percent sign, @code{%}, then it is a
comment.

@ftable @code
@anchor{makeindex preamble}
@item preamble
Preamble of the output file. Defines the context in which the index is
formatted.  Default: @code{"\\begin@{theindex@}\n"}.

@anchor{makeindex postamble}
@item postamble
Postamble of the output file.  Default: @code{"\n\n\\end@{theindex@}\n"}.

@anchor{makeindex group skip}
@item group_skip
@findex \indexspace
Traditionally index items are broken into groups, typically a group for
entries starting with @samp{a}, etc.  This specifier gives what is
inserted when a new group begins.  Default: @code{"\n\n \\indexspace\n"}
(@code{\indexspace} is a rubber length with default value @code{10pt
plus5pt minus3pt}).

@anchor{makeindex letheadflag}
@item lethead_flag
An integer.  It governs what is inserted for a new group or letter.  If
it is 0 (which is the default) then other than @code{group_skip} nothing
will be inserted before the group. If it is positive then at a new
letter the @code{lethead_prefix} and @code{lethead_suffix} will be
inserted, with that letter in uppercase between them.  If it is negative
then what will be inserted is the letter in lowercase.  The default
is@tie{}0.

@anchor{makeindex lethead prefix}
@item lethead_prefix
If a new group begins with a different letter then this is the prefix
inserted before the new letter header.  Default: @code{""}

@anchor{makeindex lethead suffix}
@item lethead_suffix
If a group begins with a different letter then this is the suffix
inserted after the new letter header.  Default: @code{""}.

@anchor{makeindex item 0}
@item item_0 
What is put between two level@tie{}0 items.  Default: @code{"\n \\item
"}.

@anchor{makeindex item 1}
@item item_1
Put between two level@tie{}1 items.  Default: @code{"\n \\subitem "}.

@anchor{makeindex item 2}
@item item_2
put between two level@tie{}2 items.  Default: @code{"\n \\subsubitem "}.

@anchor{makeindex item 01}
@item item_01
What is put between a level@tie{}0 item and a level@tie{}1 item.
Default: @code{"\n \\subitem "}.

@anchor{makeindex item x1}
@item item_x1
What is put between a level@tie{}0 item and a level@tie{}1 item in the
case that the level@tie{}0 item doesn't have any page numbers (as in
@code{\index@{aaa|see@{bbb@}@}}).  Default: @code{"\n \\subitem "}.

@anchor{makeindex item 12}
@item item_12
What is put between a level@tie{}1 item and a level@tie{}2 item.
Default: @code{"\n \\subsubitem "}.

@anchor{makeindex item x2}
@item item_x2
What is put between a level@tie{}1 item and a level@tie{}2 item, if the
level@tie{}1 item doesn't have page numbers.  Default: @code{"\n
\\subsubitem "}.

@anchor{makeindex delim 0}
@item delim_0
Delimiter put between a level@tie{}0 key and its first page
number. Default: a comma followed by a blank, @code{", "}.

@anchor{makeindex delim 1}
@item delim_1
Delimiter put between a level@tie{}1 key and its first page
number. Default: a comma followed by a blank, @code{", "}.

@anchor{makeindex delim 2}
@item delim_2
Delimiter between a level@tie{}2 key and its first page number. Default:
a comma followed by a blank, @code{", "}.

@anchor{makeindex delim n}
@item delim_n
Delimiter between two page numbers for the same key (at any
level). Default: a comma followed by a blank, @code{", "}.

@anchor{makeindex delim r}
@item delim_r
What is put between the starting and ending page numbers of a range.
Default: @code{"--"}.

@anchor{makeindex line max}
@item line_max
An integer.  Maximum length of an index entry's line in the output,
beyond which the line wraps.  Default: @code{72}.

@anchor{makeindex indent space}
@item indent_space
What is inserted at the start of a wrapped line.  Default:
@code{"\t\t"}.

@anchor{makeindex indent length}
@item indent_length
A number.  The length of the wrapped line indentation.  The default
@code{indent_space} is two tabs and each tab is eight spaces so the
default here is @code{16}.

@anchor{makeindex page precedence}
@item page_precedence
A document may have pages numbered in different ways.  For example, a
book may have front matter pages numbered in lowercase roman while main
matter pages are in arabic.  This string specifies the order in which
they will appear in the index.  The @command{makeindex} command supports
five different types of numerals: lowercase roman @code{r}, and numeric
or arabic @code{n}, and lowercase alphabetic @code{a}, and uppercase
roman @code{R}, and uppercase alphabetic @code{A}.  Default:
@code{"rnaRA"}.

@end ftable

@findex xindy
@cindex @command{xindy} program
There are a number of other programs that do the job
@command{makeindex} does. One is @command{xindy}, which does
internationalization and can process indexes for documents marked up
using @LaTeX{} and a number of other languages. It is highly
configurable, both in markup terms and in terms of the collating order
of the text, as described in its documentation.


@node \printindex
@subsection @command{\printindex}

@cindex index, printing
@findex \printindex

Synopsis:

@example
\printindex
@end example

@findex \printindex
Place the index into the output.

To get an index you must first include
@code{\usepackage@{makeidx@}\makeindex} in the document preamble and
compile the document, then run the system command @command{makeindex},
and then compile the document again.  @xref{Indexes} for further
discussion and an example of the use of @code{\printindex}.


@node Glossaries
@section Glossaries

@cindex glossary
@cindex glossaries
@cindex acronyms, list of
@findex \makeglossary
@findex \printglossaries

Synopsis:

@example
\usepackage@{glossaries@} \makeglossaries
  ...
\newglossaryentry@{@var{label}@}@{@var{settings}@}  
  ...
\gls@{@var{label}@}.  
  ...
\printglossaries
@end example

The @file{glossaries} package allows you to make glossaries, including
multiple glossaries, as well as lists of acronyms.

To get the output from this example, compile the document (for instance
with @code{pdflatex filename}), then run the command line command
@code{makeglossaries filename}, and then compile the document again.

@example
\documentclass@{...@}  
\usepackage@{glossaries@} \makeglossaries
\newglossaryentry@{tm@}@{%
  name=@{Turing machine@},
  description=@{A model of a machine that computes.  The model is simple
               but can compute anything any existing device can compute.
               It is the standard model used in Computer Science.@},
  @}  
\begin@{document@}  
Everything begins with the definition of a \gls@{tm@}.  
  ...
\printglossaries
\end@{document@}
@end example

@noindent
That gives two things.  In the main text it outputs @samp{... definition
of a Turing machine}.  In addition, in a separate sectional unit headed
@samp{Glossary} there appears a description list.  In boldface it says
@samp{Turing machine} and the rest of the item says in normal type
@samp{A model of a machine @dots{} Computer Science}.

@findex \makeglossary
@findex \printglossaries
@cindex @file{.glo} file
The command @code{\makeglossary} opens the file that will contain the
entry information, @file{@var{root-file}.glo}.  Put the
@code{\printglossaries} command where you want the glossaries to appear
in your document.

The @file{glossaries} package is very powerful.  For instance, besides
the commands @code{\newglossaryentry} and @code{\gls}, there are similar
commands for a list of acronyms.  See the package documentations on
CTAN.

@menu
* \newglossaryentry::  Declare the content of a glossary entry.
* \gls::               Give a page reference for a glossary entry.
@end menu


@node \newglossaryentry
@subsection @code{\newglossaryentry}

@cindex glossary, entries
@findex \newglossaryentry

Synopsis, one of: 

@example
\newglossaryentry@{@var{label}@} 
@{ 
  name=@{@var{name}@}, 
  description=@{@var{description}@}, 
  @var{other options}, ... 
@}
@end example

or

@example
\longnewglossaryentry@{@var{label}@} 
@{ 
  name=@{@var{name}@}, 
  @var{other options} ..., 
@} 
@{@var{description}@}
@end example

Declare a new entry for a glossary.  The @var{label} must be unique for
the document.  The settings associated with the label are pairs:
@code{@var{key}=@var{value}}.

This puts the blackboard bold symbol for the real numbers @BES{211D,} in the
glossary.

@example
\newglossaryentry@{R@}  
@{  
  name=@{\ensuremath@{\mathbb@{R@}@}@},  
  description=@{the real numbers@},  
@}
@end example

Use the second command form if the @var{description} spans more than one
paragraph.

For a full list of @var{key}s see the package documentation on CTAN but
here are a few.

@ftable @code
@item name
(Required.) The word, phrase, or symbol that you are defining.

@item description
(Required.) The description that will appear in the glossary.
If this has more than one paragraph then you must use the second command
form given in the synopsis.

@item plural
The plural form of @var{name}.  Refer to the plural form using
@code{\glspl} or @code{\Glspl} (@pxref{\gls}).

@item sort
How to place this entry in the list of entries that the glossary holds.

@item symbol
A symbol, such as a mathematical symbol, besides the name.

@end ftable


@node \gls
@subsection @code{\gls}

@cindex glossary, entry reference
@findex \gls

Synopsis, one of: 

@example
\gls@{@var{label}@}
\glspl@{@var{label}@}
\Gls@{@var{label}@}
\Glspl@{@var{label}@}
@end example

Refer to a glossary entry.  The entries are declared with
@code{\newglossaryentry} (@pxref{\newglossaryentry}).

This

@example
\newglossaryentry@{N@}@{%
  name=@{the natural numbers@},
  description=@{The numbers $0$, $1$, $2$, $\ldots$\@@@},
  symbol=@{\ensuremath@{\mathbb@{N@}@}@},
  @}  
  ...
Consider \gls@{N@}.
@end example

@noindent
gives the output @samp{Consider the natural numbers}.

The second command form @code{\glspl@{@var{label}@}} produces the plural
of @var{name} (by default it tries adding an @samp{s}).  The third form
capitalizes the first letter of @var{name}, as does the fourth form,
which also takes the plural.


@node Letters
@chapter Letters

@cindex letters, writing
@cindex writing letters

Synopsis: 

@example
\documentclass@{letter@}
\address@{@var{senders address}@}   % return address
\signature@{@var{sender name}@}
\begin@{document@}
\begin@{letter@}@{@var{recipient address}@}
\opening@{@var{salutation}@}
  @var{letter body}
\closing@{@var{closing text}@}
\end@{letter@}
   ...
\end@{document@}
@end example

Produce one or more letters.  

Each letter is in a separate @code{letter} environment, whose argument
@var{recipient address} often contains multiple lines separated with a
double backslash,@tie{}(@code{\\}).  For example, you might have:

@example
 \begin@{letter@}@{Ninon de l'Enclos \\
                l'h\^otel Sagonne@}
   ...
 \end@{letter@}
@end example

The start of the @code{letter} environment resets the page number to 1,
and the footnote number to 1 also.

The @var{sender address} and @var{sender name} are common to all of the
letters, whether there is one or more, so these are best put in the
preamble.  As with the recipient address, often @var{sender address}
contains multiple lines separated by a double
backslash@tie{}(@code{\\}).  @LaTeX{} will put the @var{sender name}
under the closing, after a vertical space for the traditional
hand-written signature.

Each @code{letter} environment body begins with a required
@code{\opening} command such as @code{\opening@{Dear Madam or Sir:@}}.
The @var{letter body} text is ordinary @LaTeX{} so it can contain
everything from enumerated lists to displayed math, except that commands
such as @code{\chapter} that make no sense in a letter are turned off.
Each @code{letter} environment body typically ends with a
@code{\closing} command such as @code{\closing@{Yours,@}}.

@findex \\ @r{for letters}
Additional material may come after the @code{\closing}.  You can say who
is receiving a copy of the letter with a command like @code{\cc@{the
Boss \\ the Boss's Boss@}}.  There's a similar @code{\encl} command for
a list of enclosures.  And, you can add a postscript with @code{\ps}.

@LaTeX{}'s default is to indent the sender name and the closing above it
by a length of @code{\longindentation}.  By default this is
@code{0.5\textwidth}. To make them flush left, put
@code{\setlength@{\longindentation@}@{0em@}} in your preamble.

To set a fixed date use something like
@code{\renewcommand@{\today@}@{1958-Oct-12@}}.  If put in your preamble
then it will apply to all the letters.

This example shows only one @code{letter} environment.  The three lines
marked as optional are typically omitted.

@example
\documentclass@{letter@}
\address@{Sender's street \\ Sender's town@}
\signature@{Sender's name \\ Sender's title@}
% optional: \location@{Mailbox 13@}
% optional: \telephone@{(102) 555-0101@}
\begin@{document@}
\begin@{letter@}@{Recipient's name \\ Recipient's address@}
\opening@{Sir:@}
% optional: \thispagestyle@{firstpage@}
I am not interested in entering a business arrangement with you.
\closing@{Your most humble, etc.,@}
\end@{letter@}
\end@{document@}
@end example

These commands are used with the @code{letter} class.

@menu
* \address::                       Sender's return address.
* \cc::                            Carbon copy list.
* \closing::                       Saying goodbye.
* \encl::                          List of enclosed material.
* \location::                      Sender's organizational location.
* \makelabels::                    Make address labels.
* \name::                          Sender's name, for the return address.
* \opening::                       Saying hello.
* \ps::                            Adding a postscript.
* \signature::                     Sender's signature.
* \telephone::                     Sender's phone number.
@end menu


@node \address
@section @code{\address}

@findex \address

Synopsis: 

@example
\address@{@var{senders address}@}
@end example

Specify the return address, as it appears on the letter and on the
envelope.  Separate multiple lines in @var{senders address} with a
double backslash,@tie{}@code{\\}.

Because it can apply to multiple letters this declaration is often put
in the preamble.  However, it can go anywhere, including inside an
individual @code{letter} environment.

This command is optional: if you do not use it then the letter is
formatted with some blank space on top, for copying onto pre-printed
letterhead paper.  If you do use the @code{\address} declaration then it
is formatted as a personal letter.

Here is an example.

@example
\address@{Stephen Maturin \\
         The Grapes of the Savoy@}
@end example


@node \cc
@section @code{\cc}

@findex \cc
@cindex cc list, in letters

Synopsis:

@example
\cc@{@var{name0} \\ 
     ... @}
@end example

Produce a list of names to which copies of the letter were sent.  This
command is optional.  If it appears then typically it comes after
@code{\closing}.  Put the names on different lines by separating them
with a double backslash, @code{\\}, as in:

@example
\cc@{President \\
    Vice President@}
@end example


@node \closing
@section @code{\closing}

@findex \closing
@cindex letters, ending
@cindex closing letters

Synopsis:

@example
\closing@{@var{text}@}
@end example

Produce the letter's closing.  This is optional, but usual.  It appears
at the end of a letter, above a handwritten signature.  For example:

@example
\closing@{Regards,@}
@end example


@node \encl
@section @code{\encl}

@findex \encl
@cindex enclosure list

Synopsis:

@example
\encl@{@var{first enclosed object} \\ 
       ... @}
@end example

Produce a list of things included with the letter. This command is
optional; when it is used, it typically is put after @code{\closing}.
Separate multiple lines with a double backslash, @code{\\}.

@example
\encl@{License \\
      Passport@}
@end example


@node \location
@section @code{\location}

@findex \location

Synopsis:

@example
\location@{@var{text}@}
@end example

The @var{text} appears centered at the bottom of the page.  It only
appears if the page style is @code{firstpage}.


@node \makelabels
@section @code{\makelabels}

@findex \makelabels

Synopsis:

@example
\makelabels   % in preamble
@end example

Optional, for a document that contains @code{letter} environments.  If
you just put @code{\makelabels} in the preamble then at the end of the
document you will get a sheet with labels for all the recipients, one
for each letter environment, that you can copy to a sheet of peel-off
address labels.

Customize the labels by redefining the commands @code{\startlabels},
@code{\mlabel}, and @code{\returnaddress} (and perhaps @code{\name}) in
the preamble.  The command @code{\startlabels} sets the width, height,
number of columns, etc., of the page onto which the labels are printed.
The command @code{\mlabel@{@var{return address}@}@{@var{recipient
address}@}} produces the two labels (or one, if you choose to ignore the
@var{return address}) for each letter environment. The first argument,
@var{return address}, is the value returned by the macro
@code{\returnaddress}.  The second argument, @var{recipient address}, is
the value passed in the argument to the @code{letter} environment.  By
default @code{\mlabel} ignores the first argument, the @var{return
address}, causing the default behavior described in the prior paragraph.

This illustrates customization.  Its output includes a page with two
columns having two labels each.

@example
\documentclass@{letter@}
\renewcommand*@{\returnaddress@}@{Fred McGuilicuddy \\
                               Oshkosh, Mineola 12305@}
\newcommand*\originalMlabel@{@}
\let\originalMlabel\mlabel
\def\mlabel#1#2@{\originalMlabel@{@}@{#1@}\originalMlabel@{@}@{#2@}@}
\makelabels
  ...
\begin@{document@}
\begin@{letter@}@{A Einstein \\
               112 Mercer Street \\
               Princeton, New Jersey, USA 08540@}
  ...
\end@{letter@}
\begin@{letter@}@{K G\"odel \\
               145 Linden Lane \\
               Princeton, New Jersey, USA 08540@}
  ...
\end@{letter@}
\end@{document@}
@end example

@noindent
The first column contains the return address twice.  The second column
contains the address for each recipient.

@PkgIndex{envlab}
The package @code{envlab} makes formatting the labels easier, with
standard sizes already provided.  The preamble lines
@code{\usepackage[personalenvelope]@{envlab@}} and @code{\makelabels}
are all that you need to print envelopes.


@node \name
@section @code{\name}

@findex \name

Synopsis:

@example
\name@{@var{name}@}
@end example

Optional.  Sender's name, used for printing on the envelope together
with the return address.


@node \opening
@section @code{\opening}

@findex \opening
@cindex letters, starting

Synopsis:

@example
\opening@{@var{salutation}@}
@end example

Required.  Follows the @code{\begin@{letter@}@{...@}}. The argument
@var{salutation} is mandatory.  For instance:

@example
\opening@{Dear John:@}
@end example


@node \ps
@section @code{\ps}
@findex \ps
@cindex postscript, in letters

Synopsis:

@example 
\ps@{@var{text}@}
@end example

Add a postscript.  This command is optional and usually is used after
@code{\closing}.

@example
\ps@{P.S. After you have read this letter, burn it. Or eat it.@}
@end example


@node \signature
@section @code{\signature}

Synopsis:

@example 
\signature@{@var{first line} \\
            ... @}
@end example

@findex \signature

The sender's name.  This command is optional, although its inclusion is
usual.

The argument text appears at the end of the letter, after the closing.
@LaTeX{} leaves some vertical space for a handwritten
signature. Separate multiple lines with a double
backslash,@tie{}@code{\\}.  For example:

@example
\signature@{J Fred Muggs \\
           White House@}
@end example

@LaTeX{}'s default for the vertical space from the @code{\closing} text
down to the @code{\signature} text is @code{6\medskipamount}, which is
six times @code{\medskipamount} (where @code{\medskipamount} is equal to
a @code{\parskip}, which in turn is defined by default here to
0.7@dmn{em}).

This command is usually in the preamble, to apply to all the letters in
the document.  To have it apply to one letter only, put it inside a
@code{letter} environment and before the @code{\closing}.

You can include a graphic in the signature as here.

@example
\signature@{\vspace@{-6\medskipamount@}\includegraphics@{sig.png@}\\
             My name@}
@end example

@noindent
For this you must put @code{\usepackage@{graphicx@}} in the preamble
(@pxref{Graphics}).


@c I think this is not a user-level command; it is used to keep from breaking
@c the page between the closing and the signature
@c @node \stopbreaks and \startbreaks
@c @section @code{\stopbreaks} and @code{\startbreaks}

@c @findex \startbreak
@c @findex \stopbreaks

@c @example 
@c @code{\stopbreaks}
@c text
@c @code{\startbreaks}
@c @end example

@c The @code{\stopbreaks} inhibits page breaking.  The @code{\startbreaks} resumes
@c normal page breaking.
@c
@c
@node \telephone
@section @code{\telephone}

@findex \telephone

Synopsis:

@example
\telephone@{@var{number}@}
@end example

The sender's telephone number.  This is typically in the preamble, where
it applies to all letters.  This only appears if the @code{firstpage}
pagestyle is selected.  If so, it appears on the lower right of the
page.


@node Terminal input/output
@chapter Terminal input/output

@cindex input/output, to terminal
@cindex terminal input/output

@menu
* \typein::             Read text from the terminal.
* \typeout::            Write text to the terminal.
@end menu


@node \typein
@section @code{\typein}

@findex \typein

Synopsis, one of:

@example
\typein@{@var{prompt-msg}@}
\typein[@var{cmd}]@{@var{prompt-msg}@}
@end example

Print @var{prompt-msg} on the terminal and cause @LaTeX{} to stop and
wait for you to type a line of input.  This line of input ends when you
hit the return key.

For example, this

@example
As long as I live I shall never forget \typein@{Enter student name:@}
@end example

@noindent
coupled with this command line interaction

@example
Enter student name:

\@@typein=Aphra Behn
@end example

@noindent
gives the output @samp{... never forget Aphra Behn}.

The first command version, @code{\typein@{@var{prompt-msg}@}}, causes
the input you typed to be processed as if it had been included in the
input file in place of the @code{\typein} command.

In the second command version the optional argument @code{@var{cmd}}
argument must be a command name --- it must begin with a backslash, \.
This command name is then defined or redefined to be the input that you
typed.  For example, this

@example
\typein[\student]@{Enter student name:@}
\typeout@{Recommendation for \student .@}
@end example

@noindent
gives this output on the command line,

@example
Enter student name:

\student=John Dee
Recommendation for John Dee.
@end example

@noindent
where the user has entered @samp{John Dee.}


@node \typeout
@section @code{\typeout}

@findex \typeout

Synopsis:

@example
\typeout@{@var{msg}@}
@end example

Print @code{msg} on the terminal and in the @code{log} file.

This

@example
\newcommand@{\student@}@{John Dee@}
\typeout@{Recommendation for \student .@}
@end example

@noindent
outputs @samp{Recommendation for John Dee}.  Like what happens here with
@code{\student}, commands that are defined with @code{\newcommand} or
@code{\renewcommand} (among others) are replaced by their definitions
before being printed.

@LaTeX{}'s usual rules for treating multiple spaces as a single space
and ignoring spaces after a command name apply to @code{msg}.  As above,
use the command @code{\space} to get a single space, independent of
surrounding spaces.  Use @code{^^J} to get a newline.  Get a percent
character with @code{\csname @@percentchar\endcsname}.

This command can be useful for simple debugging, as here:

@example
\newlength@{\jhlength@}
\setlength@{\jhlength@}@{5pt@}
\typeout@{The length is \the\jhlength.@}
@end example

@noindent
produces on the command line @samp{The length is 5.0pt}.


@node Command line
@chapter Command line

@cindex command line

Synopsis (from a terminal command line):

@example
pdflatex @var{options} @var{argument}
@end example

Run @LaTeX{} on @var{argument}.  In place of @command{pdflatex} you can
also use @command{xelatex}, or @code{lualatex}, or @code{dviluatex}, or
@code{latex}.

For example, this will run @LaTeX{} on the file @file{thesis.tex},
creating the output @file{thesis.pdf}.

@example
pdflatex thesis
@end example

@noindent
@findex .tex, @r{default extension}
Note that @file{.tex} is the default file extension.

pdf@TeX{} is a development of the original @TeX{} program, as are
Xe@TeX{} and Lua@TeX{} (@pxref{@TeX{} engines}).  They are completely
backward compatible.  But the original program had a custom output
format, DVI, while the newer ones can output directly to PDF.  This
allows them to take advantage of the extra features in PDF such as
hyperlinks, support for modern image formats such as JPG and PNG, and
ubiquitous viewing programs.  In short, if you run @command{pdflatex} or
@command{xelatex} or @command{lualatex} then you will by default get PDF
and have access to all its modern features.  If you run @command{latex},
or @code{dvilualatex}, then you will get DVI.  The description here
assumes pdf@LaTeX{}.

@xref{Command line options}, for a selection of the most useful
command line options. As to @var{argument}, the usual case is that it
does not begin with a backslash, so the system takes it to be the name
of a file and it compiles that file. If @var{argument} begins with a
backslash then the system will interpret it as a line of @LaTeX{}
input, which can be used for special effects (@pxref{Command line
input}).

If you gave no arguments or options then @command{pdflatex} prompts for
input from the terminal. You can escape from this by entering
@code{<control>-D}.

If @LaTeX{} finds an error in your document then by default it stops and
asks you about it.  @xref{Recovering from errors} for an outline of what
to do.

@menu
* Command line options::     Read text from the terminal.
* Command line input::       Write text to the terminal.
* Recovering from errors::   When something goes wrong.
@end menu


@node Command line options
@section Command line options

@cindex options, command line

These are the command-line options relevant to ordinary document
authoring. For a full list, try running @samp{latex --help} from the
command line.

With many implementations you can specify command line options by
prefixing them with @samp{-} or @samp{--}.  This is the case for
both @TeX{} Live (and Mac@TeX{}) and MiK@TeX{}.  We will use both
conventions interchangeably.

@table @code
@findex --version @r{command-line option}
@item -version
Show the current version, like @samp{pdfTeX 3.14159265-2.6-1.40.16 (TeX
Live 2015/Debian)} along with a small amount of additional information,
and exit.

@findex --help @r{command-line option}
@item -help
Give a brief usage message that is useful as a prompt and exit.

@findex --interaction @r{command-line option}
@item -interaction=@var{mode}
@TeX{} compiles a document in one of four interaction modes:
@code{batchmode}, @code{nonstopmode}, @code{scrollmode},
@code{errorstopmode}. In @dfn{errorstop mode} (the default), @TeX{}
stops at each error and asks for user intervention. In @dfn{batch
mode} it prints nothing on the terminal, errors are scrolled as if the
user hit @code{<return>} at every error, and missing files cause the
job to abort. In @dfn{nonstop mode}, diagnostic message appear on the
terminal but as in batch mode there is no user interaction. In
@dfn{scroll mode}, @TeX{} only stops for missing files or keyboard
input.

For instance, starting @LaTeX{} with this command line

@example
pdflatex -interaction=batchmode @var{filename}
@end example

@noindent
eliminates most terminal output.

@findex --jobname @r{command-line option}
@item -jobname=@var{string}
Set the value of @TeX{}'s @code{jobname} to the string.  The log file
and output file will then be named @file{@var{string}.log} and
@file{@var{string}.pdf}.

When you run @code{@command{pdflatex} @var{options} @var{argument}}, if
@var{argument} does not start with a backslash then @TeX{} considers it
the name of a file to input. Otherwise it waits for the first
@code{\input} instruction and the name of the input file will be the job
name. This is used to name the log file the output file.  The
@code{jobname} option overrides that process and directly specifies the
name.  @xref{Command line input} for an example of its use.

@findex --output-directory @r{command-line option}
@item -output-directory=@var{directory}
Write files in the directory @var{directory}.  It must already exist.

@findex --shell-escape @r{command-line option}
@findex --no-shell-escape @r{command-line option}
@findex --enable-write18 @r{command-line option}
@findex --disable-write18 @r{command-line option}
@item --shell-escape
@itemx --no-shell-escape
@itemx --enable-write18
@itemx --disable-write18
Enable or disable @code{\write18@{@var{shell command}@}}.  The first two
options are for with @TeX{} Live or Mac@TeX{} while the second two are
for MiK@TeX{}.

@PkgIndex{sagetex}
Sometimes you want to run external system commands from inside a
@LaTeX{} file. For instance the package @file{sagetex} allows you to
have the mathematics software system @i{Sage} do calculations or draw
graphs and then incorporate that output in your document.  For this
@TeX{} provides the @code{\write18} command.

But with this functionality enabled, security issues could happen if you
compiled a @LaTeX{} file from the Internet.  By default @code{\write18}
is disabled.  (More precisely, by default @TeX{} Live, Mac@TeX{}, and
MiK@TeX{} only allow the execution of a limited number of @TeX{}-related
programs, which they distribute.)

If you invoke @LaTeX{} with the option @code{no-shell-escape}, and in
your document you call @code{\write18@{ls -l@}}, then you do not get an
error but the log file says @samp{runsystem(ls -l)...disabled}.

@findex --halt-on-error @r{command-line option}
@item -halt-on-error
Stop processing at the first error.

@findex --file-line-error @r{command-line option}
@findex --no-file-line-error @r{command-line option}
@item -file-line-error
@item -no-file-line-error
Enable or disable @code{@var{filename}:@var{lineno}:@var{error}}-style
error messages.  These are only available with @TeX{} Live or Mac@TeX{}.
@end table


@node Command line input
@section Command line input

@cindex input, on command line

As part of the command line invocation @code{pdflatex @var{options}
@var{argument}} you can specify arbitrary @LaTeX{} input by starting
@var{argument} with a backslash. This allows you to do some special
effects.

@PkgIndex{hyperref}
For example, this file (which uses the @file{hyperref} package for
hyperlinks) can produce two kinds of output, one for paper and one for a
PDF.

@example
\ifdefined\paperversion        % in preamble
\newcommand@{\urlcolor@}@{black@}
\else
\newcommand@{\urlcolor@}@{blue@}
\fi
\usepackage[colorlinks=true,urlcolor=\urlcolor]@{hyperref@}
  ...
\href@{https://www.ctan.org@}@{CTAN@}  % in body
  ...
@end example 

@noindent
Compiling this document @file{book.tex} with the command line
@code{pdflatex book} will give the @samp{CTAN} link in blue.  But
compiling it with @code{pdflatex "\def\paperversion@{@}\input book.tex"}
has the link in black.  (Note the use of double quotes to prevent
interpretation of the symbols by the command line shell; your system may
do this differently.)

In a similar way, from the single file @file{main.tex} you can compile
two different versions.

@c credit Paul Gaborit: https://tex.stackexchange.com/a/220101/121234
@example
pdflatex -jobname=students "\def\student@{@}\input@{main@}"
pdflatex -jobname=teachers "\def\teachers@{@}\input@{main@}"
@end example

@noindent
The @code{jobname} option is there because otherwise both files would be
called @file{main.pdf} and the second would overwrite the first.

A final example.  This loads the package @file{graphicx} with the option
@code{draft}

@c credit Herbert Voss: https://tex.stackexchange.com/a/17236/121234
@example
pdflatex -jobname=aa "\RequirePackage[draft]@{graphicx@}\input@{aa.tex@}"
@end example

@noindent
so the graphic files are read for their size information but not
incorporated into the PDF.  (The @code{jobname} option is there because
otherwise the output file would be @file{graphicx.pdf}, as
@code{\RequirePackage} does an @code{\input} of its own.)


@node Recovering from errors
@section Recovering from errors

If @LaTeX{} finds an error in your document then it gives you an error
message and prompts you with a question mark, @code{?}.  For instance,
running @LaTeX{} on this file

@example
\newcommand@{\NP@}@{\ensuremath@{\textbf@{NP@}@}@}
The \PN@{@} problem is a million dollar one.
@end example

@noindent
causes it show this, and wait for input.

@example
! Undefined control sequence.
l.5 The \PN
           @{@} problem is a million dollar one.
? 
@end example

@noindent
The simplest thing is to enter @samp{x} and @code{<return>} and fix the
typo.  You could instead enter @samp{?} and @code{<return>} to see other
options.

@cindex @samp{*} prompt
@cindex prompt, @samp{*}
@findex \stop
There are two other error scenarios.  The first is that you forgot to
include the @code{\end@{document@}} or misspelled it.  In this case
@LaTeX{} gives you a @samp{*} prompt.  You can get back to the command
line by typing @code{\stop} and @code{<return>}.

The last scenario is that you mistyped the file name.  For instance,
instead of @code{pdflatex test} you might type @code{pdflatex tste}.

@example
! I can't find file `tste'.
<*> tste
        
(Press Enter to retry, or Control-D to exit)
Please type another input file name:
@end example

@noindent
The simplest thing is to enter @code{<Control>} and @samp{d} (holding
them down at the same time), and then retype the correct command line.


@node Document templates
@appendix Document templates

@cindex document templates
@cindex templates, document

Although not reference material, perhaps these document templates will
be useful.  Additional template resources are listed at
@url{http://tug.org/interest.html#latextemplates}.

@menu
* beamer template::
* article template::
* book template::
* Larger book template::
* tugboat template::
@end menu


@node beamer template
@section @code{beamer} template

@cindex @code{beamer} template and class
@cindex template, @code{beamer}

The @code{beamer} class creates presentation slides.  It has a vast
array of features, but here is a basic template:

@verbatim
\documentclass{beamer}

\title{Beamer Class template}
\author{Alex Author}
\date{July 31, 2007}

\begin{document}

\maketitle

% without [fragile], any {verbatim} code gets mysterious errors.
\begin{frame}[fragile]
 \frametitle{First Slide}

\begin{verbatim}
  This is \verbatim!
\end{verbatim}

\end{frame}

\end{document}
@end verbatim

One web resource for this:
@url{http://robjhyndman.com/hyndsight/beamer/}.


@node article template
@section @code{article} template

@cindex template, @code{article}

@verbatim
\documentclass{article}
\title{Article Class Template}
\author{Alex Author}

\begin{document}
\maketitle

\section{First section}
Some text.

\subsection{First section, first subsection}
Additional text.

\section{Second section}
Some more text.
\end{document}
@end verbatim


@node book template
@section @code{book} template

@cindex template, @code{book}

This is a straightforward template for a book.  See @xref{Larger book
template} for a more elaborate one.

@verbatim
\documentclass{book}
\title{Book Class Template}
\author{Alex Author}

\begin{document}
\maketitle

\chapter{First}
Some text.

\chapter{Second}
Some other text.

\section{A subtopic}
The end.
\end{document}
@end verbatim


@node Larger book template
@section Larger @code{book} template

@cindex template, @code{book}

This is a more elaborate template for a book.  It has
@code{\frontmatter}, @code{\mainmatter}, and @code{\backmatter} to
control the typography of the three main areas of a book
(@pxref{\frontmatter & \mainmatter & \backmatter}).  The book has a
bibliography and an index.

Notable is that it uses @code{\include} and @code{\includeonly}
(@pxref{Splitting the input}).  While you are working on a chapter you
can comment out all the other chapter entries from the argument to
@code{\includeonly}.  That will speed up compilation without losing any
information such as cross-references.  (Material that does not need to
come on a new page is brought in with @code{\input} instead of
@code{\include}.  You don't get the cross-reference benefit this way.)

@verbatim
\documentclass[titlepage]{book}
\usepackage{makeidx}\makeindex

\title{Book Class Template}
\author{Alex Author}

\includeonly{%
  frontcover,
  preface,
  chap1,
  ...
  }
\begin{document}
\frontmatter
\include{frontcover}
  % maybe comment out while drafting:
\maketitle \input{dedication} \input{copyright}
\tableofcontents
\include{preface}
\mainmatter
\include{chap1}
...
\appendix
\include{appena}
...
\backmatter
\bibliographystyle{apalike}
\addcontentsline{toc}{chapter}{Bibliography}
\bibliography
\addcontentsline{toc}{chapter}{Index}
\printindex
\include{backcover}
\end{document}
@end verbatim


@node tugboat template
@section @code{tugboat} template

@cindex template, TUGboat
@cindex TUGboat template
@cindex @code{ltugboat} class

@cite{TUGboat} is the journal of the @TeX{} Users Group,
@url{http://tug.org/TUGboat}.

@verbatim
\documentclass{ltugboat}

\usepackage{graphicx}
\usepackage{ifpdf}
\ifpdf
\usepackage[breaklinks,hidelinks]{hyperref}
\else
\usepackage{url}
\fi

%%% Start of metadata %%%

\title{Example \TUB\ article}

% repeat info for each author.
\author{First Last}
\address{Street Address \\ Town, Postal \\ Country}
\netaddress{user (at) example dot org}
\personalURL{http://example.org/~user/}

%%% End of metadata %%%

\begin{document}

\maketitle

\begin{abstract}
This is an example article for \TUB{}.
Please write an abstract.
\end{abstract}

\section{Introduction}

This is an example article for \TUB, linked from
\url{http://tug.org/TUGboat/location.html}.

We recommend the \texttt{graphicx} package for image inclusions, and the
\texttt{hyperref} package if active urls are desired (in the \acro{PDF}
output).  Nowadays \TUB\ is produced using \acro{PDF} files exclusively.

The \texttt{ltugboat} class provides these abbreviations (and many more):
% verbatim blocks are often better in \small
\begin{verbatim}[\small]
\AllTeX \AMS \AmS \AmSLaTeX \AmSTeX \aw \AW
\BibTeX \CTAN \DTD \HTML
\ISBN \ISSN \LaTeXe
\mf \MFB
\plain \POBox \PS
\SGML \TANGLE \TB \TP
\TUB \TUG \tug
\UNIX \XeT \WEB \WEAVE

\, \bull \Dash \dash \hyph

\acro{FRED} -> {\small[er] fred}  % please use!
\cs{fred}   -> \fred
\meta{fred} -> <fred>
\nth{n}     -> 1st, 2nd, ...
\sfrac{3/4} -> 3/4
\booktitle{Book of Fred}
\end{verbatim}

For references to other \TUB\ issue, please use the format
\textsl{volno:issno}, e.g., ``\TUB\ 32:1'' for our \nth{100} issue.

This file is just a template.  The \TUB\ style documentation is the
\texttt{ltubguid} document at \url{http://ctan.org/pkg/tugboat}.  (For
\CTAN\ references, where sensible we recommend that form of url, using
\texttt{/pkg/}; or, if you need to refer to a specific file location,
\texttt{http://mirror.ctan.org/\textsl{path}}.)

Email \verb|tugboat@tug.org| if problems or questions.

\bibliographystyle{plain}  % we recommend the plain bibliography style
\nocite{book-minimal}      % just making the bibliography non-empty
\bibliography{xampl}       % xampl.bib comes with BibTeX

\makesignature
\end{document}
@end verbatim


@node Index
@unnumbered Index

@c Keep `Command Index' working for ltx-help.el.
@anchor{Command Index}

@printindex cp

@bye

\def\DeclareTextCommand{\foo}{T1}
%    then |\foo| is defined to be |\T1-cmd \foo \T1\foo|,
%    %    where |\T1\foo| is \emph{one} control sequence, not two!
\newcommand

\def\ProvideTextCommand -- same with \providecommand
\@onlypreamble\DeclareTextCommand
\@onlypreamble\DeclareTextSymbol
\gdef\TextSymbolUnavailable#1{%
\@onlypreamble\def\DeclareTextCommandDefault#1{%
\def\ProvideTextCommandDefault#1{%
\def\DeclareTextAccent#1#2#3{%
\def\DeclareTextCompositeCommand#1#2#3#4{%
\@onlypreamble\def\DeclareTextComposite#1#2#3#4{%
\def\UseTextAccent#1#2#3{%
\def\UseTextSymbol#1#2{%
\@onlypreamble\DeclareTextSymbolDefault@item
\@onlypreamble\DeclareTextAccentDefault@item
\def\UndeclareTextCommand#1#2{%

@c Local Variables:
@c ispell-dictionary: "english"
@c coding: latin-1-unix
@c End: