From e0c6872cf40896c7be36b11dcc744620f10adf1d Mon Sep 17 00:00:00 2001 From: Norbert Preining Date: Mon, 2 Sep 2019 13:46:59 +0900 Subject: Initial commit --- help/uk-tex-faq/faq-bits+pieces.tex | 1174 +++++++++++++++++++++++++++++++++++ 1 file changed, 1174 insertions(+) create mode 100644 help/uk-tex-faq/faq-bits+pieces.tex (limited to 'help/uk-tex-faq/faq-bits+pieces.tex') diff --git a/help/uk-tex-faq/faq-bits+pieces.tex b/help/uk-tex-faq/faq-bits+pieces.tex new file mode 100644 index 0000000000..113d1139e4 --- /dev/null +++ b/help/uk-tex-faq/faq-bits+pieces.tex @@ -0,0 +1,1174 @@ +% $Id: faq-bits+pieces.tex,v 1.32 2014/01/28 18:17:36 rf10 Exp rf10 $ + +\section{Bits and pieces of \AllTeX{}} + +\Question[Q-dvi]{What is a \acro{DVI} file?} + +`\acro{DVI}' is supposed to be an acronym for +\acro{D}e\acro{V}ice-\acro{I}ndependent, meaning that the file may be +processed for printing or viewing on most kinds of typographic output +device or display. + +A \acro{DVI} file (that is, a file with the type or extension +\extension{dvi}) is the main output file of ``original'' \tex{} (later +\tex{}-like systems, such as \Qref*{\pdftex{}}{Q-whatpdftex} may use +other formats). + +A \acro{DVI} file contains all the information that is needed for +printing or previewing, except for the actual bitmaps or outlines of +fonts, and any material to be introduced by means of % !line break +\Qref*{\csx{special} commands}{Q-specials}. Characters in the +\acro{DVI} file (representing glyphs for printing or display) appear +in an encoding determined in the document. + +Any \TeX{} input file should produce the same \acro{DVI} file +regardless of which implementation of \TeX{} is used to produce it. + +An \acro{DVI} file may be processed by a \Qref*{DVI driver}{Q-driver} +to produce further output designed specifically for a particular +printer, or for output in another format (for distribution), or it may +be used by a previewer for display on a computer screen. + +Note that \Qref*{\xetex{}}{Q-xetex} (released some time after +\pdftex{}) uses an ``extended \acro{DVI} format'' (\acro{XDV}) to send +its output to a close-coupled \Qref*{\acro{DVI} driver}{Q-driver}, +\ProgName{xdvipdfmx}. + +The canonical reference for the structure of a \acro{DVI} file is the +source of Knuth's program \ProgName{dvitype} (whose original purpose, +as its name implies, was to view the content of a \acro{DVI} file). +A partially complete ``standard'' for the way they should be +processed may offer further enlightenment. +\begin{ctanrefs} +\item[\nothtml{rmfamily}DVI processing standard]\CTANref{dvistd} +\item[dvitype]\CTANref{dvitype} +\end{ctanrefs} +\LastEdit{2013-03-15} + +\Question[Q-driver]{What is a \acro{DVI} driver?} + +A \acro{DVI} driver is a program that takes as input a +\Qref*{\acro{DVI} file}{Q-dvi} +and (usually) produces a file in a format that something \emph{other} +than a \TeX{}-related program can process. + +A driver may be designed for producing output for printing (e.g., +\PS{}), for later processing (e.g., \PS{} for inclusion in a later +document), or for document exchange (e.g., \acro{PDF}). + +As well as the \acro{DVI} file, the driver typically also needs font +information. Font information may be held as bitmaps or as outlines, +or simply as a set of pointers into the fonts that a printer itself +provides. Each driver will expect the font information in a particular +form. + +For more information on the forms of font information, see +\Qref[questions]{\acro{PK} files}{Q-pk}, +% ! line break +\Qref[]{\acro{TFM} files}{Q-tfm}, +\Qref[]{virtual fonts}{Q-virtualfonts} +and \Qref[]{Using \PS{} fonts with \TeX{}}{Q-usepsfont}. +\LastEdit{2011-10-10} + +\Question[Q-pk]{What are \acro{PK} files?} + +\acro{PK} files (packed raster) are the canonical form of \tex{} font +bitmaps. The output from \Qref*{\MF{}}{Q-useMF} includes a generic +font (\acro{GF}) file and the utility \ProgName{gftopk} produces a +\acro{PK} file from that. + +There are potentially a lot of \acro{PK} files, as one +is needed for each font: that is for each magnification of each +design (point) size for each weight for each font in each family. + +Further, since the \acro{PK} files for one printer do not necessarily +work well for another, the whole set needs to be duplicated for each +printer type at a site. + +While this menagerie of bitmaps can (in principle) provide fonts that +are closely matched to the capabilities of each printer, the size of +the collection (and the resulting difficulty of maintaining it) has +been a potent driver to the move towards outline fonts such as +\Qref*{Adobe Type 1 fonts}{Q-adobetypen}. +\LastEdit{2012-10-20} + +\Question[Q-tfm]{What are \acro{TFM} files?} + +\acro{TFM} is an acronym for `\TeX{} Font Metrics'; \acro{TFM} files hold +information about the sizes of the characters of the font in question, +and about ligatures and kerns within that font. One \acro{TFM} file is +needed for each font used by \TeX{}, that is for each design (point) +size for each weight for each family; each \acro{TFM} file serves for all +magnifications of `its' font, so that there are (typically) fewer +\acro{TFM} files than there are \Qref*{\acro{PK}}{Q-pk} files. \TeX{}, +\LaTeX{}, etc.,\@ +themselves need only know about the sizes of characters and their +interactions with each other, but not what characters look like. By +contrast, \acro{TFM} files are not, in principle, needed by the +\acro{DVI} driver, which only needs to know about the glyphs that each +character selects, so as to print or display them. + +Note that TrueType and OpenType fonts contain the necessary metrics, +so that \Qref{\xetex{}}{Q-xetex} and \Qref{\luatex{}}{Q-luatex}, using +such fonts, have no need of \acro{TFM} files. A corollary of this is +that setting up fonts for use by these engines is far \emph{easier}. +\LastEdit{2012-10-20} + +\Question[Q-virtualfonts]{What are virtual fonts?} + +Virtual fonts provide a means of collecting bits and pieces together +to make the glyphs of a font: the bits and pieces may be glyphs from +``other'' fonts, rules and other ``basic'' typesetting commands, and +the positioning information that specifies how everything comes +together. + +An early instance of something like virtual fonts for \TeX{} was +implemented by David Fuchs to use an unusual printer. However, for +practical purposes for the rest of us, virtual fonts date from when Knuth +specified a format and wrote some support software, in 1989 (he +published an % ! line break +\href{http://tug.org/TUGboat/tb11-1/tb27knut.pdf}{article in \textsl{TUGboat}} +at the time; a plain text copy is available on \acro{CTAN}). + +Virtual fonts provide a way of telling \TeX{} about something more +complicated than just a one-to-one character mapping. \TeX{} reads a +\acro{TFM} file of the font, just as before, but the \acro{DVI} +processor will read the \acro{VF} and use its content to specify how +each glyph is to be processed. + +The virtual font may contain commands: +\begin{itemize} +\item to `open' one or more (real) fonts for subsequent use, +\item to remap a glyph from one of the (real) fonts for use in the + virtual font, +\item to build up a more complicated effect (using \acro{DVI} commands). +\end{itemize} + +% !this has to be generated as a new paragraph by the translator, so +% leave the blank line in place +In practice, the most common use of virtual fonts is to remap +Adobe Type 1 fonts (see \Qref[question]{font metrics}{Q-metrics}), +though there has also been useful useful work building `fake' maths +fonts (by bundling glyphs from several fonts into a single virtual +font). Virtual Computer Modern fonts, making a % ! line break +\Qref*{Cork encoded}{Q-ECfonts} font from Knuth's originals by using +remapping and fragments of \acro{DVI} for single-glyph `accented +characters', were the first ``Type~1 format'' Cork-encoded Computer +Modern fonts available. + +Virtual fonts are normally created in a single \acro{ASCII} \acro{VPL} +(Virtual Property List) file, which includes two sets of information. +The \ProgName{vptovf} utility will use the \acro{VPL} file to create +the binary \acro{TFM} and \acro{VF} files. + +A ``how-to'' document, explaining how to generate a \acro{VPL}, +describes the endless hours of fun that may be had, doing the job by +hand. Despite the pleasures to be had, the commonest way (nowadays) +of generating an \acro{VPL} file is to use the +\ProgName{fontinst} package, which is described in more detail +\htmlonly{together with the discussion of} +\Qref[in answer]{\PS{} font metrics}{Q-metrics}. +\Package{Qdtexvpl} is another utility for creating ad-hoc virtual +fonts (it uses \TeX{} to parse a description of the virtual font, and +\ProgName{qdtexvpl} itself processes the resulting \acro{DVI} file). +\begin{ctanrefs} +\item[fontinst]\CTANref{fontinst} +\item[\nothtml{\rmfamily}Knuth on virtual fonts]\CTANref{vf-knuth} +\item[\nothtml{\rmfamily}Virtual fonts ``how to'']\CTANref{vf-howto} +\item[qdtexvpl]\CTANref{qdtexvpl} +\end{ctanrefs} +\LastEdit{2012-10-20} + +\Question[Q-whatmacros]{What are (\TeX{}) macros} + +\TeX{} is a \emph{macro processor}: this is a computer-science-y term +meaning ``text expander'' (more or less); \TeX{} typesets text as it +goes along, but \emph{expands} each macro it finds. \TeX{}'s macros +may include instructions to \TeX{} itself, on top of the simple text +generation one might expect. + +Macros are a \emph{good thing}, since they allow the user to +manipulate documents according to context. For example, the macro +\csx{TeX} is usually defined to produce ``TEX'' with the `E' lowered +(the original idea was Knuth's), +but in these \acro{FAQ}s the default definition of the macro is +overridden, and it simply expands to the letters ``TeX''. (\emph{You} +may not think this a good thing, but the author of the macros has his +reasons~-- see \Qref[question]{\TeX{}-related logos}{Q-logos}.) + +Macro names are conventionally built from a \texttt{\textbackslash } +followed by a sequence of letters, which may be upper or lower case +(as in \csx{TeX}, mentioned above). They may also be % ! line break +\texttt{\textbackslash \meta{any single character}}, which allows all +sorts of oddities (many built in to most \TeX{} macro sets, all the +way up from the apparently simple `\csx{ }' meaning ``insert a space +here''). + +Macro programming can be a complicated business, but at their very +simplest they need little introduction~--- you'll hardly need to be +told that: +\begin{quote} +\begin{verbatim} +\def\foo{bar} +\end{verbatim} +\end{quote} +replaces each instance of \csx{foo} with the text ``bar''. The +command \csx{def} is \plaintex{} syntax for defining commands; +\LaTeX{} offers a macro \csx{newcommand} that goes some way towards +protecting users from themselves, but basically does the same thing: +\begin{quote} +\begin{verbatim} +\newcommand{\foo}{bar} +\end{verbatim} +\end{quote} +Macros may have ``arguments'' , which are used to substitute for marked +bits of the macro expansion: +\begin{quote} +\begin{verbatim} +\def\foo#1{This is a #1 bar} +... +\foo{2/4}. +\end{verbatim} +\end{quote} +which produces: +\begin{quote} + This is a 2/4 bar. +\end{quote} +or, in \LaTeX{} speak: +\begin{quote} +\begin{verbatim} +\newcommand{\foo}[1]{This is a #1 bar} +... +\foo{3/4}. +\end{verbatim} +\end{quote} +which produces: +\begin{quote} + This is 3/4 bar. +\end{quote} +(\latex{} users waltz through life, perhaps?) + +You will have noticed that the arguments, above, were enclosed in +braces (\texttt{\obracesymbol{}\dots{}\cbracesymbol{}}); this is the +normal way of typing arguments, though \TeX{} is enormously flexible, +and you may find all sorts of other ways of passing arguments (if you +stick with it). + +Macro writing can get very complicated, very quickly. If you are a +beginner \AllTeX{} programmer, you are well advised to read something +along the lines of the \Qref*{\TeX{}book}{Q-tex-books}; once you're under +way, \Qref*{\TeX{} by Topic}{Q-ol-books} is possibly a more satisfactory +choice. Rather a lot of the answers in these \acro{FAQ}s tell you +about various issues of how to write macros. +\LastEdit{2011-10-12} + +\Question[Q-specials]{\csx{special} commands} + +\TeX{} provides the means to express things that device drivers can +do, but about which \TeX{} itself knows nothing. For example, \TeX{} +itself knows nothing about how to include \PS{} figures into +documents, or how to set the colour of printed text; but some device +drivers do. + +Instructions for such things are introduced to your document by means +of \csx{special} commands; all that \TeX{} does with these commands is +to expand their +arguments and then pass the command to the \acro{DVI} file. In most +cases, there are macro packages provided (often with the driver) that +provide a human-friendly interface to the \csx{special}; for example, +there's little point including a figure if you leave no gap for it in +your text, and changing colour proves to be a particularly fraught +operation that requires real wizardry. \LaTeXe{} +has standard graphics and colour packages that make figure inclusion, +rotation and scaling, and colour typesetting relatively +straightforward, despite the rather daunting \csx{special} commands +involved. (\CONTeXT{} provides similar support, though not by way of +packages.) + +The allowable arguments of \csx{special} depend on the device driver +you're using. Apart from the examples above, there are \csx{special} +commands in the em\TeX{} drivers (e.g., \ProgName{dvihplj}, \ProgName{dviscr}, +\emph{etc}.)~that will draw lines at arbitrary orientations, and +commands in \ProgName{dvitoln03} that permit the page to be set in +landscape orientation. + +Note that \csx{special} behaves rather differently in \PDFTeX{}, since +there is no device driver around. There \emph{is} a concept of +\acro{PDF} specials, but in most cases \csx{special} will provoke a +warning when used in \PDFTeX{}. +\LastEdit{2011-10-15} + +\Question[Q-write]{Writing (text) files from \tex{}} + +\TeX{} allows you to write to output files from within your document. +The facility is handy in many circumstances, but it is vital for +several of the things \latex{} (and indeed almost any higher-level +\tex{}-based macro package) does for you. + +The basic uses of writing to an external file are ``obvious''~--- +remembering titles of sections for a table of contents, remembering +label names and corresponding section or figure numbers, all for a +later run of your document. However, the ``non-obvious'' thing is +easy to forget: that page numbers, in \tex{}, are slippery beasts, and +have to be captured with some care. The trick is that \csx{write} +operations are only executed as the page is sent to the \acro{DVI} +or \acro{PDF} file. Thus, if you arrange that your page-number macro +(\csx{thepage}, in \latex{}) is not expanded until the page is +written, then the number written is correct, since that time is where +\tex{} guarantees the page number tallies with the page being sent +out. + +Now, there are times when you want to write something straight away: +for example, to interact with the user. \TeX{} captures that +requirement, too, with the primitive command \csx{immediate}: +\begin{quote} +\begin{verbatim} +\immediate\write\terminal{I'm waiting...} +\end{verbatim} +\end{quote} +writes a ``computer-irritates-user'' message, to the terminal. + +Which brings us to the reason for that \csx{terminal}. \TeX{} can +``\csx{write}'' up to 16 streams simultaneously, and that argument to +\csx{write} says which is to be used. Macro packages provide the +means of allocating streams for your use: \plaintex{} provides a macro +\csx{newwrite} (used as ``\csx{newwrite}\csx{streamname}'', which sets +\csx{streamname} as the stream number). In fact, \csx{terminal} (or +its equivalent) is the first output stream ever set up (in most macro +packages): it is never attached to a file, and if \tex{} is asked to +write to \emph{any} stream that isn't attached to a file it will send +the output to the terminal (and the log). +\LastEdit{2011-10-15} + +\Question[Q-spawnprog]{Spawning programs from \AllTeX{}: \csx{write18}} + +The \tex{} \Qref*{\csx{write} primitive instruction}{Q-write} is used +to write to different file `streams'; TeX refers to each open file by +a number, not by a file name (although most of the time we hide this). +Originally, \tex{} would write to a file connected to a stream +numbered 0--15. More recently, a special ``stream 18'' has been +implemented: it is not writing to a file, but rather tells TeX to ask +the operating system to do something. To run a command, we put it as +the argument to \csx{write18}. So to run the \progname{epstopdf} +utility on a file with name stored as \csx{epsfilename}, we would +write: +\begin{quote} +\begin{verbatim} +\write18{epstopdf \epsfilename} +\end{verbatim} +\end{quote} +When using something like the \Package{epstopdf} package, the `stream' +write operation is hidden away and you don't need to worry about the +exact way it's done. + +However, there is a security issue. If you download some \alltex{} code from +the Internet, can you be sure that there is not some command in it +(perhaps in a hidden way) to do stuff that might be harmful to your +computer (let's say: delete everything on the hard disk!)? In the +face of this problem, both \miktex{} and \tex{}~Live have, for some +time, disabled \csx{write18} by default. To turn the facility on, +both distributions support an additional argument when starting \tex{} +from the command shell: +\begin{quote} +\begin{verbatim} +(pdf)(la)tex --shell-escape +\end{verbatim} +\end{quote} +The problem with this is that many people use \alltex{} via a graphical +editor, so to use \csx{write18} for a file the editor's settings must +be changed. Of course, the settings need restoring after the file is +processed: you defeat the point of the original protection, that way. + +The latest \miktex{} (version 2.9), and recent \tex{}~Live (from the +2010 release) get +around this by having a special ``limited'' version of \csx{write18} +enabled `out of the box'. The idea is to allow only a pre-set list of +commands (for example, \BibTeX{}, \progname{epstopdf}, \tex{} itself, +and so on). Those on the list are regarded as safe enough to allow, +whereas anything else (for example deleting files) still needs to be +authorised by the user. This seems to be a good balance: most people +most of the time will not need to worry about \csx{write18} at all, +but it will be available for things like \Package{epstopdf}. + +Note that the \tex{} system may tell you that the mechanism is in use: +\begin{wideversion} +\begin{quote} +\begin{verbatim} +This is pdfTeX, Version 3.1415926-1.40.11 (TeX Live 2010) + restricted \write18 enabled. +\end{verbatim} +\end{quote} +\end{wideversion} +\begin{narrowversion} +\begin{quote} +\begin{verbatim} +This is pdfTeX, Version 3.1415926-1.40.11 + (TeX Live 2010) + restricted \write18 enabled. +\end{verbatim} +\end{quote} +\end{narrowversion} +when it starts. +\begin{ctanrefs} +\item[epstopdf.sty]Distributed with Heiko Oberdiek's packages + \CTANref{oberdiek}[epstopdf-pkg] +\end{ctanrefs} +\LastEdit{2012-12-03} + +\Question[Q-hyphen]{How does hyphenation work in \TeX{}?} + +Everyone knows what hyphenation is: we see it in most books we read, +and (if we're alert) will spot occasional ridiculous mis-hyphenation +(at one time, British newspapers were a fertile source). + +Hyphenation styles are culturally-determined, and the same language +may be hyphenated differently in different countries~--- for example, +British and American styles of hyphenation of English are very +different. As a result, a typesetting system that is not restricted +to a single language at a single locale needs to be able to change its +hyphenation rules from time to time. + +\TeX{} uses a pretty good system for hyphenation (originally designed +by Frank Liang~--- you may view his % ! line break +\href{http://tug.org/docs/liang/}{Ph.D.\ thesis} online) and while +it's capable of missing ``sensible'' hyphenation points, it seldom +selects grossly wrong ones. The +algorithm matches candidates for hyphenation against a set of +``hyphenation patterns''. The candidates for hyphenation must be +sequences of letters (or other single characters that \TeX{} may be +persuaded to think of as letters). Non-letters interrupt hyphenation; +this applies to \TeX{}'s \csx{accent} primitive (as in `syst\`eme') +just as much as the exclamation in`syst!eme'. + +(Hyphenation takes place on the characters ``sent to the printer''. +The problem with \csx{accent} is avoided~---in \latex{}~--- by the use +of the \Package{fontenc} package, as discussed in % ! line break +``\Qref*{Accented words aren t hyphenated}{Q-hyphenaccents}''.) + +Sets of hyphenation patterns are usually derived from analysis of +a list of valid hyphenations (the process of derivation, using a tool +called \Package{patgen}, is not ordinarily a sport to be played by +ordinary mortals). + +The patterns for the languages a \TeX{} system is going to deal with +may only be loaded when the system is installed. To change the set of +hyphenation patterns recognised by a \tex{}-based or \xetex{} system, +a \Qref*{partial reinstallation}{Q-newlang} is necessary (note that +\Qref*{\luatex{}}{Q-luatex} relaxes this constraint). + +\TeX{} provides two ``user-level'' commands for control of +hyphenation: \csx{language} (which selects a hyphenation style), and +\csx{hyphenation} (which gives explicit instructions to the hyphenation +engine, overriding the effect of the patterns). + +The ordinary \LaTeX{} user need not worry about \csx{language}, since +it is very thoroughly managed by the \Package{babel} package; use of +\csx{hyphenation} is discussed in +\begin{wideversion} + the context of +\end{wideversion} +% beware line wrap +\Qref[question]{hyphenation failure}{Q-nohyph}. +\LastEdit{2012-12-03} + +\Question[Q-clsvpkg]{What are \LaTeX{} classes and packages?} + +\latex{} aims to be a general-purpose document processor. Such an aim +could be achieved by a selection of instructions which would enable +users to use \tex{} primitives, but such a procedure is considered too +inflexible (and probably too daunting for ordinary users). Thus the +designers of \latex{} created a model which offered an +\emph{abstraction} of the design of documents. Obviously, not all +documents can look the same (even with the defocussed eye of +abstraction), so the model uses \emph{classes} of document. Base +\latex{} offers five classes of document: \Class{book}, +\Class{report}, \Class{article} and \Class{letter}. +For each class, \latex{} provides a \emph{class file}; the user +arranges to use it via a \csx{documentclass} command at the top of the +document. So a document starting +\begin{quote} + \cmdinvoke{documentclass}{article} +\end{quote} +may be called ``an \emph{article} document''. + +This is a good scheme, but it has a glaring flaw: the actual +typographical designs provided by the \latex{} class files aren't +widely liked. The way around this is to \emph{refine} the class. To +refine a class, a programmer may write a new class file that loads an +existing class, and then does its own thing with the document design. + +If the user finds such a refined class, all is well, but if not, the +common way is to load a \emph{package} (or several). + +The \latex{} distribution, itself, provides rather few package files, +but there are lots of them, by a wide variety of authors, to be found +on the archives. Several packages are designed just to adjust the +design of a document~--- using such packages achieves what the +programmer might have achieved by refining the class. + +Other packages provide new facilities: for example, the +\Package{graphics} package (actually provided as part of any \latex{} +distribution) allows the user to load externally-provided graphics +into a document, and the \Package{hyperref} package enables the user +to construct hyper-references within a document. + +On disc, class and package files only appear different by virtue of +their name ``extension''~--- class files are called \File{*.cls} while +package files are called \File{*.sty}. Thus we find that the \LaTeX{} +standard \Class{article} class is represented on disc by a file called +\File{article.cls}, while the \Package{hyperref} package is +represented on disc by a file called \File{hyperref.sty}. + +The class vs.~package distinction was not clear in \LaTeXo{}~--- +everything was called a style (``document style'' or ``document style +option''). It doesn't really matter that the nomenclature has +changed: the important requirement is to understand what other people +are talking about. +\LastEdit{2013-10-21} + +\Question[Q-whatenv]{What are \latex{} ``environments''} + +While \tex{} makes direct provision for commands, \latex{} adds a +concept of ``environment''; environments perform an action on a block +(of something or other) rather than than just doing something at one +place in your document. + +A totally trivial environment could change the font in use for a chunk +of text, as +\begin{quote} +\begin{verbatim} +\newenvironment{monoblock}% + {\ttfamily}% + {} +\end{verbatim} +\end{quote} +which defines a \environment{monoblock} which may be used as +\begin{quote} +\begin{verbatim} +\begin{monoblock} + some text set in monospace +\end{monoblock} +\end{verbatim} +\end{quote} +which will look like: +\begin{quote} + \texttt{some text set in monospace} +\end{quote} +so it is a particularly simple example. A rather complicated +environment is introduced by \cmdinvoke{begin}{document}; it looks +simple, but needs all sorts of special \tex{} code to make it work +`transparently'; most environments are more elaborate than +\environment{monoblock} and \emph{much} simpler than +\environment{document}. + +An environment puts its content inside a \tex{} \emph{group}, so that +commands used inside the environment don't `leak out'~--- the +\environment{monoblock} environment, above, restricts its effect to +its own contents (the stuff between the \cmdinvoke{begin}{monoblock} +and \cmdinvoke{end}{monoblock}), which is just what you need for this +sort of thing. + +So that's ``simple'' environments; the \environment{monoblock}, above +doesn't actually gain us much over +\begin{quote} +\begin{verbatim} +{\ttfamily some text set in monospace} +\end{verbatim} +\end{quote} +though in fact many useful environments are just as simple (to look +at). Some, such as \environment{verbatim}, look simple but are +actually very tricky inside. + +\latex{} also allows arguments to an environment: +\begin{quote} +\begin{verbatim} +\newenvironment{fontblock}[1]% + {#1\selectfont}% + {} +\end{verbatim} +\end{quote} +and use of \environment{fontblock} as: +\begin{quote} +\begin{verbatim} +\begin{fontblock}{\ttfamily} +\end{verbatim} +\end{quote} +would produce the same effect as the \environment{monoblock} +environment. + +Environments may also have optional arguments, in much the same way as +commands: +\begin{quote} +\begin{verbatim} +\newenvironment{normaltext}[1][\itshape]% + {#1}% + {} +\end{verbatim} +\end{quote} +which will ordinarily set its body in italic, but +\begin{quote} +\begin{verbatim} +\begin{normaltext}[\ttfamily] + ... +\end{normaltext} +\end{verbatim} +\end{quote} +will observe its optional argument, and behave the same as the +\environment{monoblock} we started with. + +Note that an environments argument(s) (mandatory or optional) are +\emph{not} passed to the `\csx{end}' text of the environment~--- that +is specified as a macro with no arguments, so that +\begin{quote} +\begin{verbatim} +\newenvironment{normaltext}[1][\itshape]% + {#1}% + {\typeout{what was #1, again?} +\end{verbatim} +\end{quote} +produces an error message +\begin{quote} +\begin{verbatim} +! Illegal parameter number in definition of \endnormaltext. +\end{verbatim} +\end{quote} +So, if you need to pass an environment argument to the end-code, you +have to wrap it in a macro of its own: +\begin{quote} +\begin{verbatim} +\newenvironment{normaltext}[1][Intro]% + {#1% + \newcommand{\foo}{#1}}% + {\typeout{what was \foo{}, again?} +\end{verbatim} +\end{quote} +\LastEdit*{2013-02-20} + +\Question[Q-dtx]{Documented \LaTeX{} sources (\extension{dtx} files)} + +\LaTeXe{}, and many contributed \latex{} macro packages, are written +in a \Qref*{literate programming style}{Q-lit}, with source and +documentation in the +same file. This format in fact originated before the +days of the \LaTeX{} project as one of the ``Mainz'' series of +packages. A documented source file conventionally has the suffix +\extension{dtx}, and will normally be `stripped' before use with +\LaTeX{}; an installation (\extension{ins}) file is normally provided, +to automate this process of removing comments for speed of loading. +If the \extension{ins} file is available, you may process \emph{it} +with \latex{} to produce the package (and, often, auxiliary files). + +Output should look something like: +\begin{quote} +\begin{verbatim} +Generating file(s) ./foo.sty + +Processing file foo.dtx (package) -> foo.sty +File foo.dtx ended by \endinput. +Lines processed: 2336 +Comments removed: 1336 +Comments passed: 2 +Codelines passed: 972 +\end{verbatim} +\end{quote} +The lines ``\texttt{Processing \dots{}\ ended by \csx{endinput}}'' may +be repeated if the \extension{dtx} file provides more than one +`unpacked' file. + +To read the comments ``as a document'', you can run \LaTeX{} on the +\extension{dtx} file to produce a nicely formatted version of the +documented code. (Most \latex{} packages on \ctan{}, nowadays, already +have \acro{PDF} of the result of processing the \extension{dtx} file, +as ``documentation''.) + +Several packages may be included in one \extension{dtx} file, with +conditional sections, and there are facilities for indexes of macros, +etc. All of this m\'elange is sorted out by directives in the +\extension{ins} file; conventional indexing utilities may be necessary +for ``full'' output. + +Anyone may write \extension{dtx} files; the format is explained in +\Qref*{The \LaTeX{} Companion}{Q-latex-books}, and a tutorial is available +from \acro{CTAN} (which comes with skeleton \extension{dtx} and +\extension{ins} files). + +Composition of \extension{dtx} files is supported in \ProgName{emacs} by +\Qref*{\acro{AUC}-\TeX{}}{Q-editors}. + +The (unix-based) script \ProgName{dtxgen} generates a proforma basic +\extension{dtx} file, which could be useful when starting a new +project. + +Another route to an \extension{dtx} file is to write the +documentation and the code separately, and then to combine them using +the \ProgName{makedtx} system. This technique has particular value in +that the documentation file can be used separately to generate +\acro{HTML} output; it is often quite difficult to make % ! line break +\Qref*{\LaTeX{} to \acro{HTML} conversion}{Q-LaTeX2HTML} tools deal +with \extension{dtx} files, since they use an unusual class file. + +The \ProgName{sty2dtx} system goes one step further: it attempts to +create a \extension{dtx} file from a `normal' \extension{sty} file +with comments. It works well, in some circumstances, but can become +confused by comments that aspire to ``structure'' (e.g., tabular +material, as in many older packages' file headers). + +The \extension{dtx} files are not used by \LaTeX{} after they have been +processed to produce \extension{sty} or \extension{cls} (or whatever) +files. They need not be kept with the working system; however, for +many packages the \extension{dtx} file is the primary source of +documentation, so you may want to keep \extension{dtx} files elsewhere. + +An interesting sideline to the story of \extension{dtx} files is the +\Package{docmfp} package, which extends the model of the \Package{doc} +package to +\begin{flatversion} + \MF{} and \MP{} (\Qref[see questions]{}{Q-MF} and \Qref[\nothtml]{}{Q-MP}) +\end{flatversion} +\begin{hyperversion} + \Qref{\MF{}}{Q-MF} and \Qref{\MP{}}{Q-MP}, +\end{hyperversion} +thus permitting documented distribution of bundles containing code for +\MF{} and \MP{} together with related \LaTeX{} code. +\begin{ctanrefs} +\item[AUC-TeX]\CTANref{auctex} +\item[clsguide.pdf]\CTANref{clsguide} +\item[docmfp.sty]\CTANref{docmfp} +\item[docstrip.tex]Part of the \LaTeX{} distribution +\item[DTX tutorial]\CTANref{dtxtut} +\item[dtxgen]\CTANref{dtxgen} +\item[makedtx]\CTANref{makedtx} +\item[sty2dtx]\CTANref{sty2dtx} +\end{ctanrefs} +\LastEdit{2014-06-03} + +\Question[Q-whatenc]{What are encodings?} + +Let's start by defining two concepts, the \emph{character} and the +\emph{glyph}. +The character is the abstract idea of the `atom' of a +language or other dialogue: so it might be a letter in an alphabetic +language, a syllable in a syllabic language, or an ideogram in an +ideographic language. The glyph is the mark created on screen or +paper which represents a character. Of +course, if reading is to be possible, there must be some agreed +relationship between the glyph and the character, so while the precise +shape of the glyph can be affected by many other factors, such as the +capabilities of the writing medium and the designer's style, the +essence of the underlying character must be retained. + +Whenever a computer has to represent characters, someone has to define +the relationship between a set of numbers and the characters they +represent. This is the essence of an encoding: it is a mapping +between a set of numbers and a set of things to be represented. + +\TeX{} of course deals in encoded characters all the time: the +characters presented to it in its input are encoded, and it emits +encoded characters in its \acro{DVI} or \acro{PDF} output. These +encodings have rather different properties. + +The \TeX{} input stream was pretty unruly back in the days when Knuth +first implemented the language. Knuth himself prepared documents on +terminals that produced all sorts of odd characters, and as a result +\TeX{} contains some provision for translating its input (however +encoded) to something regular. Nowadays, +the operating system translates keystrokes into a code appropriate for +the user's language: the encoding used is usually a national or +international standard, though some operating systems use ``code +pages'' (as defined by Microsoft). These standards and code pages often +contain characters that may not appear in the \TeX{} system's input +stream. Somehow, these characters have to be dealt with~--- so +an input character like ``\'e'' needs to be interpreted by \TeX{} in +a way that that at least mimics the way it interprets ``\csx{'}\texttt{e}''. + +The \TeX{} output stream is in a somewhat different situation: +characters in it are to be used to select glyphs from the fonts to be +used. Thus the encoding of the output stream is notionally a font +encoding (though the font in question may be a +% beware line break (twice) +\nothtml{virtual one~--- see }% +\Qref[question]{virtual font}{Q-virtualfonts}). In principle, a +fair bit of what appears in the output stream could be direct +transcription of what arrived in the input, but the output stream +also contains the product of commands in the input, and translations +of the input such as ligatures like % +\texttt{fi}\nothtml{\ensuremath\Rightarrow``fi''}. + +Font encodings became a hot topic when the +\Qref*{Cork encoding}{Q-ECfonts} +appeared, because of the possibility of suppressing +\csx{accent} commands in the output stream (and hence improving the +quality of the hyphenation of text in inflected languages, which is +interrupted by the \csx{accent} commands~--- see +% beware line break +\Qref[question]{``how does hyphenation work''}{Q-hyphen}). +To take advantage of the diacriticised characters represented in the +fonts, it is necessary to arrange that whenever the +command sequence ``\csx{'}\texttt{e}'' has been input +(explicitly, or implicitly via the sort of mapping of input mentioned +above), the character that codes the position of the ``\'e'' glyph is +used. + +Thus we could have the odd arrangement that the diacriticised character in +the \TeX{} input stream is translated into \TeX{} commands that would +generate something looking like the input character; this sequence of +\TeX{} commands is then translated back again into a single +diacriticised glyph as the output is created. This is in fact +precisely what the \LaTeX{} packages \Package{inputenc} and +\Package{fontenc} do, if operated in tandem on (most) characters in +the \acro{ISO}~Latin-1 input encoding and the \acro{T}1 font encoding. +At first sight, it seems eccentric to have the first package do a thing, and +the second precisely undo it, but it doesn't always happen that way: +most font encodings can't match the corresponding input encoding +nearly so well, and the two packages provide the sort of symmetry the +\LaTeX{} system needs. + +\Question[Q-ECfonts]{What are the \acro{EC} fonts?} + +A font provides a number of \emph{glyphs}. In order that the glyphs +may be printed, they are \Qref*{\emph{encoded}}{Q-whatenc}, and the +encoding is used as an index into tables within the font. For various +reasons, Knuth chose deeply eccentric encodings for his Computer +Modern family of fonts; in particular, he chose different encodings +for different fonts, so that the application using the fonts has to +remember which font of the family it's using before selecting a +particular glyph. + +When \TeX{} version 3 arrived, most of the drivers for the +eccentricity of Knuth's encodings went away, and at \acro{TUG}'s Cork +meeting, an encoding for a set of 256 glyphs, for use in \TeX{} text, +was defined. The intention was that these glyphs should cover `most' +European languages that use Latin alphabets, in the sense of including +all accented letters needed. (Knuth's \acro{CMR} fonts missed things +necessary for Icelandic and Polish, for example, which the Cork fonts +do have, though even Cork encoding's coverage isn't complete.) +\latex{} refers to the Cork encoding as \acro{T}1, and provides the +means to use fonts thus encoded to avoid problems with the interaction +of accents and hyphenation % ! line break +(see \Qref[question]{hyphenation of accented words}{Q-hyphenaccents}). + +The first \MF{}-fonts to conform to the Cork encoding were the \acro{EC} +fonts. They look \acro{CM}-like, though their metrics differ from \acro{CM}-font +metrics in several areas. They have long been regarded as `stable' (in +the same sense that the \acro{CM} fonts are stable: their metrics are +unlikely ever to change). Each \acro{EC} font is, of course, roughly twice the +size of the corresponding \acro{CM} font, and there are far more of them than +there are CM fonts. The simple number of fonts proved problematic in +the production of Type~1 versions of the fonts, but \acro{EC} or +\acro{EC}-equivalent fonts in Type~1 or TrueType form (the latter only from +\begin{wideversion} + \Qref{commercial suppliers}{Q-commercial}). +\end{wideversion} +\begin{narrowversion} + % ( <- paren matching + commercial suppliers~--- \Qref{question}{Q-commercial}). +\end{narrowversion} +Free \Qref*{auto-traced versions}{Q-textrace}~--- the \acro{CM}-super and +the \acro{LGC} fonts, and the Latin Modern series (rather directly generated +from Metafont sources), are available. + +Note that the Cork encoding doesn't cover mathematics (so that no +``T1-encoded'' font families can not support it). If you're using +Computer-Modern-alike fonts, this doesn't actually matter: your system +will have the original Computer Modern mathematical fonts (or the +those distributed with the Latin Modern set), which cover `basic' \TeX{} +mathematics; more advanced mathematics are likely to need separate +fonts anyway. Suitable mathematics fonts for use with other font +families are discussed in % ! line break +``\Qref*{choice of scalable fonts}{Q-psfchoice}''. + +The \acro{EC} fonts are distributed with a set of `Text Companion' (\acro{TC}) fonts +that provide glyphs for symbols commonly used in text. The \acro{TC} fonts +are encoded according to the \latex{} \acro{TS}1 encoding, and are not +necessarily as `stable' are the \acro{EC} fonts are. Note that modern +distributions tend not to distribute the \acro{EC} fonts in outline format, but +rather to provide Latin Modern for \acro{T}1-encoded Computer Modern-style +fonts. This can sometimes cause confusion when users are recompiling +old documents. + +The Cork encoding is also implemented by virtual fonts provided in the +\acro{PSNFSS} system, for Adobe Type 1 fonts, and also by most other such +fonts that have been developed (or otherwise made available) for use +with \alltex{}. + +Note that \acro{T}1 (and other eight-bit font encodings) are superseded in +the developing \TeX{}-family members \Qref*{\xetex{}}{Q-xetex} and +\Qref*{\luatex{}}{Q-luatex}, which use Unicode as their base encoding, +and use Unicode-encoded fonts (typically in \FontFormat{ttf} or +\FontFormat{otf} formats). The \Package{cm-unicode} fonts carry the +flag in this arena, along with the Latin Modern set. +\begin{ctanrefs} +\item[CM-super fonts]\CTANref{cm-super} +\item[CM-LGC fonts]\CTANref{cm-lgc} +\item[CM unicode fonts]\CTANref{cm-unicode} +\item[EC and TC fonts]\CTANref{ec} +\item[Latin Modern fonts]\CTANref{lm} +\end{ctanrefs} + +\Question[Q-unicode]{Unicode and \tex{}} + +Unicode is a character code scheme that has the capacity to express +the text of the languages of the world, as well as important symbols +(including mathematics). Any coding scheme that is directly +applicable to \tex{} may be expressed in single bytes (expressing up +to 256 characters); Unicode characters may require several bytes, and +the scheme may express a very large number of characters. + +For ``old-style'' applications (\tex{} or \pdftex{}) to deal with +Unicode input, the sequence of bytes to make up Unicode character are +processed by a set of macros that deliver a glyph number in an +appropriate font. The macros that read these bytes is complicated, +and manifests as \pkgoption{utf8} option for the \latex{} distribution +\Package{inputenc} package; the coverage of that option is limited to +Unicode characters that can be represented using ``\latex{} standard +encodings''. The separate package \Package{ucs} provides wider, but +less robust, coverage via an \Package{inputenc} option +\pkgoption{utf8x}. As a general rule, you should never use +\pkgoption{utf8x} until you have convinced yourself that +\pkgoption{utf8} can not do the job for you. + +`Modern' \tex{}-alike applications, \Qref*{\xetex{}}{Q-xetex} and +\Qref*{\luatex{}}{Q-luatex} read their input using \acro{UTF}-8 +representations of Unicode as standard. They also use TrueType or +OpenType fonts for output; each such font has tables that tell the +application which part(s) of the Unicode space it covers; the tables +enable the engines to decide which font to use for which character +(assuming there is any choice at all). +\begin{ctanrefs} +\item[inputenc.sty]Part of the \CTANref{latex} distribution +\item[ucs.sty]\CTANref{ucs} +\end{ctanrefs} +\LastEdit{2012-04-20} + +\Question[Q-tds]{What is the \acro{TDS}?} + +\acro{TDS} is an acronym for ``\TeX{} Directory Structure''; it +specifies a standard way of organising all the \TeX{}-related files on +a computer system. + +Most modern distributions arrange their \tex{} files in conformance +with the \acro{TDS}, using both a `distribution' directory tree and a +(set of) `local' directory trees, each containing \TeX{}-related +files. The \acro{TDS} recommends the name \texttt{texmf} for the name +of the root directory (folder) of an hierarchy; in practice there are +typically several such trees, each of which has a name that compounds +that (e.g., \texttt{texmf-dist}, \texttt{texmf-var}). + +Files supplied as part of the distribution are put into the +distribution's tree, but the location of the distribution's hierarchy is +system dependent. (On a Unix system it might be at +\path{/usr/share/texmf} or \path{/opt/texmf}, or a similar location.) + +There may be more than one `local' hierarchy in which additional files +can be stored. An installation will also typically offer a local +hierarchy, while each user may have an individual local hierarchy. + +The \acro{TDS} itself is published as the output of a \acro{TUG} % ! line break +\Qref*{Technical Working Group}{Q-TUG*}. You may browse an +\href{http://tug.org/tds/}{on-line version} of the standard, and +copies in several other formats (including source) are available on +\acro{CTAN}. +\begin{ctanrefs} +\item[\nothtml{\rmfamily}\acro{TDS} specification]\CTANref{tds} +\end{ctanrefs} + +\Question[Q-eps]{What is ``Encapsulated \PS{}'' (``\acro{EPS}'')?} + +\PS{} has been for many years a \emph{lingua franca} of powerful +printers (though modern high-quality printers now tend to require some +constrained form of Adobe Acrobat, instead); since \PS{} is also a +powerful graphical programming language, it is commonly used as an +output medium for drawing (and other) packages. + +However, since \PS{} \emph{is} such a powerful language, some +rules need to be imposed, so that the output drawing may be included +in a document as a figure without ``leaking'' (and thereby destroying +the surrounding document, or failing to draw at all). + +Appendix \acro{H} of the \PS{} Language Reference Manual (second +and subsequent editions), specifies a set of rules for \PS{} to +be used as figures in this way. The important features are: +\begin{itemize} +\item certain ``structured comments'' are required; important ones are + the identification of the file type, and information about the + ``bounding box'' of the figure (i.e., the minimum rectangle + enclosing it); +\item some commands are forbidden~--- for example, a \texttt{showpage} + command will cause the image to disappear, in most \TeX{}-output + environments; and +\item ``preview information'' is permitted, for the benefit of things + such as word processors that don't have the ability to draw + \PS{} in their own right~--- this preview information may be in + any one of a number of system-specific formats, and any viewing + program may choose to ignore it. +\end{itemize} +A \PS{} figure that conforms to these rules is said to be in +``Encapsulated \PS{}'' (\acro{EPS}) format. Most \AllTeX{} packages for +including \PS{} are structured to use Encapsulated \PS{}; +which of course leads to much hilarity as exasperated \AllTeX{} users +struggle to cope with the output of drawing software whose authors +don't know the rules. + +\Question[Q-adobetypen]{Adobe font formats} +\keywords{type1 type3} + +Adobe has specified a number of formats for files to represent fonts +in \PS{} files; this question doesn't attempt to be encyclopaedic, so +we only discuss the two formats most commonly encountered in the +\AllTeX{} context, types~1 and 3. In particular, we don't discuss the +OpenType format, whose many advantages now becoming accessible to most +\AllTeX{} users (by means of +\begin{hyperversion} + the widely-used \Qref{\xetex{}}{Q-xetex} and the more experimental + \Qref{\LuaTeX{}}{Q-luatex}). +\end{hyperversion} +\begin{flatversion} + the widely-used \xetex{}~--- see \Qref[question]{}{Q-xetex}~--- and + the more experimental \LuaTeX{}~--- see \Qref[question]{}{Q-luatex}). +\end{flatversion} + +Adobe Type~1 format specifies a means to represent outlines of the glyphs +in a font. The `language' used is closely restricted, to ensure that +the font is rendered as quickly as possible. (Or rather, as quickly +as possible with Adobe's technology at the time the specification was +written: the structure could well be different if it were specified +now.) The format has long been the basis of the digital type-foundry +business, though nowadays most new fonts are released in OpenType format. + +%% Type~1 fonts are directly supported by some operating system software, +%% and at least one \TeX{} system, the commercial % line break! +%% \Qref*{\YandY{} system}{Q-commercial}, bases its entire +%% operation on the use of Type~1 fonts. + +In the \AllTeX{} context, Type~1 fonts are extremely important. Apart +from their simple +availability (there are thousands of commercial Type~1 text fonts around), the +commonest reader for \acro{PDF} files has long (in effect) \emph{insisted} on +their use (see below). + +Type~3 fonts have a more forgiving specification. A wide range of +\PS{} operators is permissible, including bitmap specifiers. Type~3 +is therefore the natural format to be used for programs such as +\ProgName{dvips} when they auto-generate something to represent +\MF{}-generated fonts in a \PS{} file. It's Adobe Acrobat Viewer's +treatment of bitmap Type~3 fonts that has made direct \MF{} output +increasingly unattractive, in recent years. If you have a \acro{PDF} +document in which the text looks fuzzy and uneven in Acrobat Reader, +ask Reader for the \texttt{File}\arrowhyph{}% +\texttt{Document Properties}\arrowhyph{}% +\texttt{Fonts ...}, and it will likely show some font or other as +``Type~3'' (usually with encoding ``Custom''). The problem has +disappeared with version 6 of Acrobat Reader. See % line break +\Qref[question]{\acro{PDF} quality}{Q-dvips-pdf} for a discussion of +the issue, and for ways of addressing it. + +Type~3 fonts should not entirely be dismissed, however. Acrobat +Reader's failure with them is entirely derived from its failure to use +the anti-aliasing techniques common in \TeX{}-ware. Choose a +different set of \PS{} graphical operators, and you can make pleasing +Type~3 fonts that don't ``annoy'' Reader. For example, you may not +change colour within a Type~1 font glyph, but there's no such +restriction on a Type~3 font, which opens opportunities for some +startling effects. + +\Question[Q-resolns]{What are ``resolutions''?} + +``Resolution'' is a word that is used with little concern for its +multiple meanings, in computer equipment marketing. The word suggests +a measure of what an observer (perhaps the human eye) can resolve; yet +we regularly see advertisements for printers whose resolution is +1200dpi~--- far finer than the unaided human eye can distinguish. The +advertisements are talking about the precision with which the printer +can place spots on the printed image, which affects the fineness of +the representation of fonts, and the accuracy of the placement of +glyphs and other marks on the page. + +In fact, there are two sorts of ``resolution'' on the printed page +that we need to consider for \AllTeX{}'s purposes: +\begin{itemize} +\item the positioning accuracy, and +\item the quality of the fonts. +\end{itemize} +In the case where \AllTeX{} output is being sent direct to a printer, +in the printer's ``native'' language, it's plain that the \acro{DVI} +processor must know all such details, and must take detailed account +of both types of resolution. + +In the case where output is being sent to an intermediate distribution +format, that has potential for printing (or displaying) we know not +where, the final translator, that connects to directly to the printer +or display, has the knowledge of the device's properties: the +\acro{DVI} processor need not know, and should not presume to guess. + +Both \PS{} and \acro{PDF} output are in this category. While \PS{} is +used less frequently for document distribution nowadays, it is +regularly used as the source for distillation into \acro{PDF}; and +\acro{PDF} is the workhorse of an enormous explosion of document +distribution. + +Therefore, we need \acro{DVI} processors that will produce +``resolution independent'' \PS{} or \acro{PDF} output; of course, the +independence needs to extend to both forms of independence outlined +above. + +Resolution-independence of fonts was for a long time forced upon the +world by the feebleness of Adobe's \ProgName{Acrobat} +\ProgName{Reader} at dealing with bitmap files: a sequence of answers +starting with one aiming at the % ! line break +\Qref*{quality of \acro{PDF} from \PS{}}{Q-dvips-pdf} addresses +the problems that arise. + +Resolution-independence of positioning is more troublesome: +\ProgName{dvips} is somewhat notorious for insisting on positioning to +the accuracy of the declared resolution of the printer. +One commonly-used approach is to declare a resolution of 8000 (``better +than any device''), and this is reasonably successful though it does +have its \Qref*{problems}{Q-8000}. + +\Question[Q-fontname]{What is the ``Berry naming scheme''?} + +In the olden days, \AllTeX{} distributions were limited by the +feebleness of file systems' ability to represent long names. (The +\MSDOS{} file system was a particular bugbear: fortunately any current +Microsoft system allows rather more freedom to specify file names. +Sadly, the ISO~9660 standard for the structure of \CDROM{}s has a +similar failing, but that too has been modified by various extension +mechanisms.) + +One area in which these short file names posed a particular problem +was that of file names for Type~1 fonts. +These fonts are distributed by their vendors with +pretty meaningless short names, and there's a natural ambition to +change the name to something that identifies the font somewhat +precisely. Unfortunately, names such as ``BaskervilleMT'' are +already far beyond the abilities of the typical feeble file system, +and add the specifier of a font shape or variant, and the difficulties +spiral out of control. Font companies deal with the issue by +inventing silly names, and providing a map file to show what the +``real'' names. Thus the Monotype Corporation provides the +translations: +\begin{quote} + \texttt{bas\_\_\_\_\_ BaskervilleMT}\\ + \texttt{basb\_\_\_\_ BaskervilleMT-Bold}\\ + \texttt{basbi\_\_\_ BaskervilleMT-BoldItalic} +\end{quote} +and so on. These names could be used within \AllTeX{} programs, +except that they are not unique: there's nothing to stop Adobe using +`\texttt{bas\_\_\_\_\_}' for \emph{their} Baskerville font. + +Thus arose the Berry naming scheme. + +The basis of the scheme is to encode the meanings of the various parts +of the file's specification in an extremely terse way, so that enough +font names can be expressed even in impoverished file name-spaces. The +encoding allocates one character to the font ``foundry'' (Adobe, Monotype, +and so on), two to the typeface name (Baskerville, Times Roman, and so +on), one to the weight, shape, and encoding and so on. + +The whole scheme is outlined in the \Package{fontname} distribution, +which includes extensive documentation and a set of tables of fonts +whose names have been systematised. +\begin{ctanrefs} +\item[fontname distribution]\CTANref{fontname} +\end{ctanrefs} + -- cgit v1.2.3