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+% -*-latex-*-
+% Document name: /u/sy/beebe/emacs/filehdr.ltx
+% Creator: Nelson H. F. Beebe [beebe@magna.math.utah.edu]
+% Creation Date: Wed Nov  6 20:51:19 1991
+
+%%% ====================================================================
+%%%  @LaTeX-file{
+%%%     author          = "Nelson H. F. Beebe",
+%%%     version         = "1.28",
+%%%     date            = "06 March 1996",
+%%%     time            = "13:34:24 MST",
+%%%     filename        = "filehdr.ltx",
+%%%     address         = "Center for Scientific Computing
+%%%                        Department of Mathematics
+%%%                        University of Utah
+%%%                        Salt Lake City, UT 84112
+%%%                        USA",
+%%%     telephone       = "+1 801 581 5254",
+%%%     FAX             = "+1 801 581 4148",
+%%%     URL             = "http://www.math.utah.edu/~beebe",
+%%%     checksum        = "10578 2582 11023 83232",
+%%%     email           = "beebe@math.utah.edu (Internet)",
+%%%     codetable       = "ISO/ASCII",
+%%%     keywords        = "file header, checksum",
+%%%     supported       = "yes",
+%%%     docstring       = "This LaTeXinfo document describes
+%%%                        filehdr.el, a GNU Emacs support package for
+%%%                        the creation and maintenance of standard
+%%%                        file headers, such as this one.  It may be
+%%%                        processed by LaTeX to produce a typeset
+%%%                        document, or by M-x latexinfo-format-buffer
+%%%                        in GNU Emacs to produce an info file for
+%%%                        on-line documentation.
+%%%
+%%%                        The checksum field above contains a CRC-16
+%%%                        checksum as the first value, followed by the
+%%%                        equivalent of the standard UNIX wc (word
+%%%                        count) utility output of lines, words, and
+%%%                        characters.  This is produced by Robert
+%%%                        Solovay's checksum utility.",
+%%%  }
+%%% ====================================================================
+
+\documentstyle[latexinfo,rcs]{book}
+
+% Comment out to suppress page footers with RCS version info:
+\RCSID{$Id: filehdr.ltx,v 1.9 1993/08/30 19:41:05 beebe Exp beebe $}
+
+\renewcommand{\i}[1]{{\em #1}}  % change from \sl to \em
+\let\emph=\i
+
+\pagestyle{empty}
+
+\newindex{cp} \c concepts
+\newindex{fn} \c functions
+\newindex{pg} \c programs
+\newindex{tp} \c persons
+\newindex{vr} \c variables
+
+\typeout{May need LaTeXinfo submode for latex.el
+for dots, emph, et al if Mike Clarkson hasn't
+fixed the problem yet.}\c
+
+\c \finalout
+
+\title{
+        Standard File Headers
+}
+
+\author{
+        Nelson H. F. Beebe\\
+        Center for Scientific Computing\\
+        Department of Mathematics\\
+        University of Utah\\
+        Salt Lake City, UT 84112\\
+        USA\\
+        Tel: +1 801 581 5254\\
+        FAX: +1 801 581 4148\\
+        E-mail: {\tt beebe@math.utah.edu}
+}
+
+\date{06 March 1996 \\
+Version 1.28}
+
+\c =================================================
+
+\begin{iftex}
+\c We need to allow hyphenation at - characters in
+\c \tt fonts.
+\global\hyphenchar\nintt = `\-
+\global\hyphenchar\tentt = `\-
+\global\hyphenchar\elvtt = `\-
+\global\hyphenchar\twltt = `\-
+\end{iftex}
+
+\begin{document}
+
+\bibliographystyle{plain}
+
+\maketitle
+
+\c =================================================
+
+\clearpage
+\vspace*{0pt plus 1filll}
+Copyright \copyright{} 1991 Free Software Foundation, Inc.
+
+This file documents version 1.28 of the standard
+file header support package for GNU Emacs, version
+18 or later.\refill
+
+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.\refill
+
+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).\refill
+
+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.\refill
+
+Permission is granted to copy and distribute
+translations of this manual into another language,
+under the above conditions for modified versions,
+except that this permission notice may be stated
+in a translation approved by the Foundation.\refill
+
+\clearpage
+\pagestyle{headings}
+\pagenumbering{roman}
+\tableofcontents
+
+% \listoftables
+
+\clearpage
+\pagenumbering{arabic}
+
+\c =================================================
+\c Anything before the \setfilename will not appear
+\c in the .info file
+\setfilename{filehdr.info}
+
+\node Top, Licensing information, Variable Index, (dir)
+
+\begin{ifinfo}
+This file documents version 1.28 of the standard
+file header support package for GNU Emacs, version 18
+or later.\refill
+
+Copyright (C) 1991 Free Software Foundation, Inc.\refill
+
+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.\refill
+
+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.\refill
+
+Permission is granted to copy and distribute
+translations of this manual into another language,
+under the above conditions for modified versions,
+except that this permission notice may be stated
+in a translation approved by the Foundation.\refill
+\end{ifinfo}
+
+\begin{menu}
+* Licensing information::     Conditions for use
+* Author and version::        Who wrote this
+* Background::                The origins of all of this
+* What's in a header?::
+* Putting it all together::
+* Outline of file headers::
+* Attribute descriptions::    Details of attributes
+* GNU Emacs editing support:: Letting Emacs do the work for you
+* Simple customization::      Changing things the easy way
+* Advanced customization::    Changing things the hard way
+* Bug reporting::             How to report bugs, comments, etc.
+* Bibliography::              Literature references
+* Concept Index::             General topic index
+* Function Index::            Lisp functions
+* Person Index::              Individuals cited in this text
+* Program Index::             Operating system programs
+* Variable Index::            Lisp variables
+\end{menu}
+
+\c =================================================
+
+\c ===> \node node-name, next, previous, up <===
+\node Licensing information, Author and version, Top, Top
+
+\c =============================================
+\c There appears to be a bug in LaTeXinfo 1.3.5
+\c \unnumberedsec{xxx} is dropped from the
+\c info file.  We cannot use \section*{} in
+\c LaTeX mode because tables of contents entries
+\c are then lost.
+\c =============================================
+
+\begin{ifinfo}
+\chapter*{Licensing information}
+\end{ifinfo}
+\begin{tex}
+\unnumbered{Licensing information}
+\end{tex}
+\cindex{licensing information}
+The program currently being distributed that
+relates to standard file headers is contained in
+the file \file{filehdr.el}.  It consists of
+numerous support functions for to the creation and
+maintenance of file headers.  This program is
+\dfn{free}; this means that everyone is free to
+use it and free to redistribute it on a free
+basis.\refill
+
+Specifically, we want to make sure that you have
+the right to give away copies of the programs that
+relate to \file{filehdr.el}, that you receive
+source code or else can get it if you want it,
+that you can change these programs or use pieces
+of them in new free programs, and that you know
+you can do these things.\refill
+
+To make sure that everyone has such rights, we
+have to forbid you to deprive anyone else of these
+rights.  For example, if you distribute copies of
+the file \file{filehdr.el}, you must give the
+recipients all the rights that you have.  You must
+make sure that they, too, receive or can get the
+source code.  And you must tell them their
+rights.\refill
+
+Also, for our own protection, we must make certain
+that everyone finds out that there is no warranty
+for the programs that relate to \file{filehdr.el}.
+If these programs are modified by someone else and
+passed on, we want their recipients to know that
+what they have is not what we distributed, so that
+any problems introduced by others will not reflect
+on our reputation.\refill
+
+The precise conditions of the licenses for the
+programs currently being distributed that relate
+to \file{filehdr.el} are found in the General Public
+Licenses that accompany them.  The programs that
+are part of GNU Emacs are covered by the GNU Emacs
+copying terms
+(\pxref{License, , , emacs, The GNU Emacs Manual}),
+and other programs are covered by licenses that
+are contained in their source files.\refill
+
+\node Author and version, Background, Licensing information, Top
+
+\c We only include this section in the info file,
+\c because the printed manual has a title page
+\c with author information.
+\begin{ifinfo}
+The GNU Emacs Lisp file \file{filehdr.el}
+was developed by\refill
+\begin{verbatim}
+Nelson H. F. Beebe
+Center for Scientific Computing
+Department of Mathematics
+University of Utah
+Salt Lake City, UT 84112
+USA
+Tel: +1 801 581 5254
+FAX: +1 801 581 4148
+E-mail: beebe@math.utah.edu
+URL: http://www.math.utah.edu/~beebe
+\end{verbatim}
+
+\noindent
+in the summer of 1991, and contributed to the Free
+Software Foundation.\refill
+
+This documentation corresponds to version 1.28 of
+\file{filehdr.el}.  This should match the code
+version that is stored in the Emacs variable
+\code{file-header-code-version}.\c
+\vindex{file-header-code-version}
+The author information is similarly stored in the variable
+\code{file-header-code-author}.\refill\c
+\vindex{file-header-code-author}
+\end{ifinfo}
+
+\node Background, What's in a header?, Author and version, Top
+
+\chapter{Background}
+
+With the rapid spread of the global Internet,
+which by 1991 reaches more than a half-million
+computers\c
+\cpsubindex{Internet}{size of}
+all around the world \cite{Lottor:CACM-34-11-21},\c
+\tindex{Lotter, Mark}
+the opportunities for free exchange of software
+and textual data are greatly enhanced.\refill
+
+While this brings exciting new capabilities to
+many people, not just those involved in academic
+research, it is hampered by several factors.\refill
+
+First, not all network file exchange\c
+\cindex{network file exchange}
+is error-free.  Electronic mail\c
+\cpsubindex{electronic mail}{corruption problems}
+systems in particular are notorious for corrupting
+information, either by truncation of lines or
+message bodies, or by transliteration or other
+altering of certain characters.  These problems
+are most severe for mail exchanges \emph{between}
+major networks, such as between the Internet and
+Usenet\c
+\cindex{Usenet}
+or Bitnet.\refill\c
+\cindex{Bitnet}
+
+Second, no standards yet exist for describing the
+contents of files.  While this is an area of
+research at some academic institutions, the wide
+variety of operating systems in use, and the growing
+numbers of computers (approaching 100 million
+on a world-wide basis in 1991), suggest that such
+standards may never exist, any more than products
+on the commercial market, from soup to saltines,
+have standard labels.\refill
+
+Third, without a record of origin of software and
+data, it is impossible for users to verify that
+they have up-to-date copies, or to contribute
+improvements and additions back to the original
+authors.\refill
+
+Fourth, without a standard means of encoding
+information in file headers, there is no hope of
+automating the process of collecting information
+from file headers to produce enhanced file archive
+summaries, catalogs, and the like.\refill
+
+During the author's 1991--92 tenure as President of the
+\TeX{} Users Group,\c
+\cindex{TeX Users Group}
+efforts were undertaken to improve the quality and
+quantity of electronic distribution of
+\TeX{}-related software and data.  While this work
+had a narrow focus, it has quite general
+ramifications, and the GNU Emacs support code here
+is quite general, and capable of handling almost
+any type of computer-readable textual
+material.\refill
+
+It does \emph{not}, however, address the issue of
+exchange of binary (non-textual) data; that has a
+number of difficulties associated with it, the two
+most severe being rigid formats intolerant of
+extension, and machine-specific encoding and byte
+order.\refill
+
+During a visit to Heidelberg University\c
+\cindex{Heidelberg University}
+in June
+1990, the author spent a pleasant brain-storming
+session that lasted until 3am with a dozen
+colleagues (who names, alas, were unrecorded) from
+Heidelberg, Mainz, Darmstadt, and Goettingen.\refill
+
+We discussed many things that evening, but one
+topic in particular led to this work: an informal
+proposal for standard file headers that could
+address all of the problems noted above.\refill
+
+\node What's in a header?, Putting it all together, Background, Top
+
+\chapter{What's in a header?}\c
+\cpsubindex{file header}{contents}
+
+The Bib\TeX{}\c
+\pindex{bibtex}
+system for support of bibliographic data bases was
+developed by Oren Patashnik\c
+\tindex{Patashnik, Oren}
+at Stanford University, based on earlier work by
+Brian Reid\c
+\tindex{Reid, Brian}
+at Carnegie Mellon University on the
+Scribe document formatting system\c
+\cindex{Scribe document formatting system}
+\cite{Unilogic:SDP84}.  Bib\TeX{} is described in
+Leslie Lamport's\c
+\tindex{Lamport, Leslie}
+book \cite{Lamport:LDP85} on
+\LaTeX{}.\c
+\cindex{LaTeX}
+It is based on the notion that bibliographic items
+can be divided into distinct \emph{classes}:
+articles, books, reports, theses, and so
+on.\refill
+
+Each class of documents has certain features in
+common.  For example, journal articles have
+authors, titles, volume numbers, often issue
+numbers, page numbers, and dates of publications.
+Theses and reports would have the name of an
+institution attached.\refill
+
+The number of classes of documents is not fixed;
+indeed, it may change with time, or between
+cultures and languages.  Thus, a bibliographic
+system must be \emph{extensible}.   Bib\TeX{}
+provides this critical feature by an
+implementation in a programming language that
+knows how to parse the general structure of a
+bibliographic data base entry, without particular
+knowledge of the classes, or attributes of
+classes.  That information is instead encoded in a
+\emph{style file}, which is written in a much more
+compact form that is specialized for its job, and
+is presumably easier for users to change than
+Bib\TeX{} itself is.\refill
+
+The style file can specify which attributes are
+required to be present in a class (e.g.\ a Ph.D.
+thesis must have an institution), and which
+attributes are optional (a book may or may not
+have an International Standard Book Number,\c
+\cindex{International Standard Book Number (ISBN)}
+ISBN).\refill
+
+Some styles may not require all attributes in a
+particular class, so Bib\TeX{} simply
+\emph{ignores} attributes not required by the
+current style, checking them only cursorily for
+proper syntax.\refill
+
+In addition, the style file can specify how individual
+bibliographic entries extracted by Bib\TeX{} from
+data base files are to be formatted.  In a
+typesetting application, this flexibility is
+important, because there are a great many
+bibliography formatting styles, and each journal
+or publisher often has rather strict (and
+arbitrary) rules that authors must adhere to.\refill
+
+How does this relate to the question of file
+headers?\refill
+
+Clearly, the notion of classes and attributes
+applies to all computer files as well.  The class
+is the file type, such as Lisp file, Pascal code
+file, and national census data file.  The
+attributes are things like author(s), author's
+address, date of last modification, file name,
+revision history, character set name, and so on.\refill
+
+In many operating systems, file naming conventions
+have been adopted by which the name encodes
+information about the class to which the file
+belongs.  For example, if the file name ends in
+\file{.c}, it is assumed to contain code written
+in the C programming language.  Unfortunately,
+few file systems are general enough to permit the
+creators of computer files to encode additional
+header information that might be more detailed.\refill
+
+Since this additional information cannot be
+standardly encoded in the file system, it must be
+supplied in some way inside the files themselves.
+This is not universally possible, particularly
+with binary files.\refill
+
+However, textual data tends to be much more
+portable between computer systems, and all
+reasonable programming languages and text
+processing systems make some provision for
+\emph{comments},\c
+\cindex{comment}
+that is, explanatory material inserted into the
+file which is otherwise ignored by the program
+which processes the file.\refill
+
+Such comments are generally identified by a unique
+start symbol, followed by the comment text, and a
+unique end symbol.\refill
+
+The start symbol is usually a particular special
+character, or special short character sequence,
+not otherwise required in the language in which
+the file is encoded.  Sometimes the start symbol
+must begin in a certain column of the line, such
+as Fortran's \code{C} or \code{*} in column 1, or
+is implicitly present at a certain column
+(assembly languages for older computers often
+decreed something like ``a comment starts in
+column 32 of the input record'').\refill
+
+The end symbol is frequently an end-of-line
+condition, which need not be an actual character.
+This convention is simple, but limits comments to
+single lines.  If a comment end symbol other than
+end-of-line is chosen, the comment body may span
+multiple lines.  Thus, the PL/1 and C programming
+languages delimit comments by \code{/*} and
+\code{*/}, and Pascal by \code{(*} and \code{*)},
+or by paired braces.  Some programming languages
+even permit comments to be properly \emph{nested},
+so that one can comment out a block of code that
+itself contains comments.\refill
+
+Ideally, a comment syntax should be simple, yet
+permit \emph{any} processor-representable
+characters to appear in the comment text, so as
+not to hinder freedom of expression.\refill
+
+In any event, with most programming languages, we
+should be able to encode file header information
+as comments in such a way that expression is not
+restricted, yet both humans and suitable computer
+programs can recognize the presence of the file
+header.\refill
+
+\node Putting it all together, Outline of file headers, What's in a header?, Top
+
+\chapter{Putting it all together}
+
+The preceding sections have outlined the notions
+of \emph{classes}, \emph{attributes}, and
+\emph{comment embedding}.  What we want to do is
+to borrow the syntax used by Bib\TeX{}\c
+\pindex{bibtex}
+for bibliography data base files, and encode the
+file header as comment body text in whatever
+syntax the programming language allows, but to do
+so in such a way that it can be readily recognized
+by both humans and computer programs.\refill
+
+Thus, in a Fortran file, for which comments run
+from a \code{C} in column 1 to end of line, our
+file header might look something like this:\refill
+\begin{verbatim}
+C     @Class{
+C       attribute1 = "value1",
+C       attribute2 = {value2},
+C       attribute3 = {value3 with {extra braces}},
+C       attribute4 = {value4 with "quotation marks"},
+C       attribute5 = "value5 with ""quotation marks""",
+C       ...
+C     }
+\end{verbatim}
+
+The key to programmatic recognition of the header
+is the syntax \emph{name followed by an opening
+brace, zero or more attribute assignments, and a
+closing brace}.  The attribute value fields can be
+enclosed in quotation marks, or balanced
+braces, as shown above.\refill
+
+In the event that braces otherwise have special
+significance (such as in one of Pascal's comment
+forms), other distinct paired delimiters could be
+used; in the ASCII character set, this means
+parentheses, square brackets, or angle
+brackets.\refill
+
+The order of attributes is significant only in the
+event of duplications; in such a case, the
+\emph{last} value assignment is the one to be
+used.  Conventions for the order of attributes
+will make file headers easier to read,
+however.\refill
+
+Readers familiar with Bib\TeX{}\c
+\cindex{citation tag}
+will note the absence of a \emph{tag} following
+the opening brace.  In the bibliography data base
+application, the tag serves as a unique citation
+key that can be placed in other documents to
+uniquely identify the bibliographic reference.  In
+the current application for file headers, we have
+no need of such a tag.\refill
+
+For languages in which comments continue from a
+start symbol to end of line, it will be useful,
+though not essential, to make the comment section
+containing the file header more visible.  This can
+be done in a variety of ways, such as by doubling
+or tripling the comment start symbol, or putting a
+distinctive character sequence, like several
+asterisks or an arrow, \code{==>}, after it.  The
+essential point is that if each line begins with a
+comment start symbol, \emph{that same prefix must
+be used on every line of the header}.  Not only
+does this enhance visibility, it makes it possible
+for a relatively simple computer program to
+identify the first line of the header and
+recognize the comment syntax automatically, and
+then collect the remainder of the header by
+discarding identical comment prefixes\c
+\cpsubindex{comment}{prefix stripping}
+from succeeding lines until a complete header has
+been collected.\refill
+
+\node Outline of file headers, Attribute descriptions, Putting it all together, Top
+
+\chapter{Outline of file headers}\c
+\cpsubindex{file header}{outline}\c
+\cindex{outline of file header}
+
+This chapter briefly describes what the file
+headers contain: class names, attribute names, and
+attribute values.  Each is treated in a separate
+section.  Detailed descriptions of attributes will
+be found in the next chapter (\pxref{Attribute
+descriptions}).\refill
+
+\begin{menu}
+* Class names::
+* Attribute names::
+* Attribute values::
+\end{menu}
+
+\node Class names, Attribute names, Outline of file headers, Top
+
+\section{Class names}\c
+\cindex{class name}
+
+What should the class name in a file header be?
+We want it to be indicative of the file contents,
+even to a reader unfamiliar with the computer
+system from which it originated.  Here are some
+desirable criteria:\refill
+\begin{itemize}
+
+\item
+The class name should \emph{not} be restricted by
+the length constraints of many file systems, and
+it should not use abbreviations, because they are
+often unintelligible to readers unfamiliar with
+the originating computer system, or with the
+language in which the header is written.\refill
+
+\item
+It must also be possible to generate the class
+name automatically from knowledge of what the file
+name is, at least for those many classes of files
+that are distinguished by particular phrases in
+their file names.\refill
+
+\item
+Class names must be standard across different
+operating systems, so that when files are moved
+between such systems, they can be readily
+associated with the correct class.\refill
+
+\item
+Class names must be recognizable by a simple
+computer program, and thus must conform to an
+agreed-upon syntax.\refill
+\end{itemize}
+
+I therefore propose that class names consist of an
+optional at-sign, \code{@}, immediately followed
+by an initial letter, optionally followed by
+letters, digits, and hyphens, followed by the
+phrase \code{-file}.\refill
+
+Letter case may be mixed for readability,
+\emph{but is not otherwise significant}:
+\code{@LATEX-FILE} and \code{@LaTeX-file}
+represent the same file class.\refill
+
+This style of naming is common to many programming
+languages.   Hyphens between words improve
+readability, while avoiding ambiguities introduced
+when spaces are allowed to be part of
+names.\refill
+
+\node Attribute names, Attribute values, Class names, Top
+
+\section{Attribute names}\c
+\cindex{attribute names}
+
+What file header attributes do we need?  Here are
+several that are desirable:
+abstract,
+author(s),
+checksum,
+code table,
+date,
+documentation,
+filename,
+keywords (for later indexing and cross-referencing),
+postal, electronic mail, and WorldWide Web addresses,
+and
+version.\refill
+
+Attribute names have the same syntax as class
+names, except that an at-sign, \code{@}, is never
+present.  New attribute names can be added as
+needed, with the understanding that the file
+header processing software will ignore attributes
+that it has not been programmed to deal
+with.\refill
+
+\node Attribute values, Outline of file headers, Attribute names, Top
+
+\section{Attribute values}\c
+\cindex{attribute values}
+
+What about attribute values?  These are for the
+most part arbitrary text strings, usually
+delimited by quotation marks.  In the event that
+quotation marks are needed in the text itself,
+braces (or parentheses, square brackets, or angle
+brackets) may be used instead, provided that they
+are properly nested.  The value text should
+\emph{not} presuppose the existence of any
+particular text formatting system;\c
+\cpsubindex{attribute value}{no formatting system}
+in particular,
+it should be understandable to a human reader when
+it is displayed in the 95 printable characters of
+the ASCII character set.\refill
+
+Attribute values may span multiple lines, and in
+most cases, newlines can be treated like spaces.\c
+\cpsubindex{attribute value}{newlines in}
+However, file header processing software
+\emph{must} distinguish between spaces and
+newlines, and in some cases, such as for address
+values, newlines will be preserved in the
+output.\refill
+
+Since file headers are encoded inside language
+comments, each line will often begin with a
+comment start symbol and white space chosen to
+provide neat formatting of the header to enhance
+its readability.  Thus, after stripping the
+comment start symbol, leading white space (blanks
+and horizontal tabs) may be ignored.\refill\c
+\cpsubindex{attribute value}{leading white space in}
+
+File header processing software \emph{may} choose
+to eliminate common prefix strings consisting of a
+comment start symbol and following white space
+from successive lines of a single value, but
+preserve additional indentation space.  Thus, the
+input\refill
+\begin{verbatim}
+;;; name = "Blah blah blah blah blah blah
+;;;         blah blah blah blah blah blah.
+;;;
+;;;              Blah blah blah blah blah.
+;;;         blah blah blah blah blah blah.
+;;;
+;;;              Blah blah blah blah blah."
+\end{verbatim}
+
+\noindent
+could produce the value string\refill
+\begin{verbatim}
+Blah blah blah blah blah blah
+blah blah blah blah blah blah.
+
+     Blah blah blah blah blah.
+blah blah blah blah blah blah.
+
+     Blah blah blah blah blah.
+\end{verbatim}
+
+\noindent
+if common prefixes are stripped, or\refill
+\begin{verbatim}
+Blah blah blah blah blah blah
+blah blah blah blah blah blah.
+
+Blah blah blah blah blah.
+blah blah blah blah blah blah.
+
+Blah blah blah blah blah.
+\end{verbatim}
+
+\noindent
+if all leading white space is discarded.\refill
+
+Bib\TeX{}\c
+\pindex{bibtex}
+adopts that convention that braced
+groups inside a value string are protected from
+certain actions, such as letter case conversion,
+or sorting.  In particular, a single quotation
+mark may be enclosed in braces to prevent its
+recognition as a value string terminator, assuming
+the string was started by a quotation mark.  Since
+Bib\TeX{} expects that its output will be
+processed by the \TeX{} typesetting system, where
+braces serve as grouping commands, and are not
+normally themselves printable, this is a
+reasonable choice: the value string \code{"A
+quotation mark, \{"\}, must be braced"} will be
+reduced by \TeX{} to \code{A quotation mark, ",
+must be braced}.\refill
+
+In the context of general file headers, this
+convention is not reasonable, because the value
+strings will not in general be processed by
+\TeX{}, but instead, will be treated as verbatim
+strings.\refill
+
+Similarly, although the C programming language has
+character escape conventions to permit encoding of
+non-printable characters in printable form, such
+as \code{\back n} for newline and \code{\back t}
+for horizontal tab, such usages are undesirable in
+the context of general file headers that must
+serve for many different programming languages and
+file types.\refill
+
+Several programming languages adopt the convention
+that a quote inside a quoted string is represented
+by an adjacent pair of quotes.  This convention is
+easy to understand, requires no additional escape
+characters, and permits unrestricted
+representation of all printable characters, and of
+course, white space (blanks and horizontal tabs).
+We adopt this convention for attribute value
+strings, but note that since balanced braces
+(parentheses, square brackets, angle brackets) can
+also be used to delimit value strings, the need
+for such doubling will be rare.\refill\c
+\cpsubindex{attribute value}{quote characters in}
+
+\node Attribute descriptions, GNU Emacs editing support, Attribute values, Top
+
+\chapter{Attribute descriptions}\c
+\cindex{attribute descriptions}
+
+In this chapter, we go into the details of each of
+the currently-defined attributes in a standard
+file header.  Attributes are treated in
+alphabetical order in the following sections; they
+need not occur in that order in file headers.\refill
+
+\begin{menu}
+* abstract::
+* address::
+* author::
+* checksum::
+* codetable::
+* date::
+* docstring::
+* email::
+* FAX::
+* filename::
+* keywords::
+* supported::
+* telephone::
+* time::
+* URL::
+* version::
+* multiple values::
+\end{menu}
+
+\node abstract, address, Attribute descriptions, Attribute descriptions
+
+\section{Abstract}\c
+\cpsubindex{attribute}{abstract}
+
+The \code{abstract}\c
+\cindex{abstract}
+attribute can supply a short abstract string to
+complement the longer \code{docstring} entry.
+This should normally be limited to a single
+paragraph.\refill
+
+For example, large research institutes often
+prepare an annual publication list with abstracts
+of documents prepared by staff members.  With care
+in the preparation of the file headers, and
+suitable software support, much of that annual
+report could be extracted automatically from the
+file headers.\refill
+
+\node address, author, abstract, Attribute descriptions
+
+\section{Address}\c
+\cpsubindex{attribute}{address}
+
+The \code{address}\c
+\cindex{address}
+attribute should have a postal
+address.  Be sure to include a country in your
+address; your file may be shared with users all
+around the world.\refill
+
+Here is an example from the file header for this
+document:\refill
+\begin{verbatim}
+%%%     address         = "Center for Scientific Computing
+%%%                        Department of Mathematics
+%%%                        University of Utah
+%%%                        Salt Lake City, UT 84112
+%%%                        USA",
+\end{verbatim}
+
+\node author, checksum, address, Attribute descriptions
+
+\section{Author}\c
+\cpsubindex{attribute}{author}
+
+The \code{author}\c
+\cindex{author}
+attribute should give the full
+name of the author, in the order as it is
+conventionally spoken.  In much of the Western
+world, the family name goes last.\refill
+
+If there are multiple authors, separate them by
+the word \code{and},\c
+\cindex{and}
+rather than by commas.  The
+reason for this is that Bib\TeX{}\c
+\cindex{name parsing}
+has special algorithms that use this convention to
+allow parsing of names in some foreign languages,
+as well as names with qualifiers, like \code{Jr.},
+and those algorithms could be adapted by other
+programs that process file headers.  Even simple
+programs could separate the names by splitting at
+the word \code{and}.\refill
+
+Here is the \code{author}\c
+\cindex{author}
+attribute from this
+document's file header:\refill
+\begin{verbatim}
+%%%     author          = "Nelson H. F. Beebe",
+\end{verbatim}
+
+\node checksum, codetable, author, Attribute descriptions
+
+\section{Checksum}\c
+\cpsubindex{attribute}{checksum}
+
+The background chapter
+(\pxref{Background})
+noted that it is important to be
+able to verify the correctness of files that are
+moved between different computing systems.  The
+way that this is traditionally handled is to
+compute a number which depends in some clever way
+on all of the characters in the file, and which
+will change, with high probability, if any
+character in the file is changed.
+Such a number is called a \emph{checksum}.\refill\c
+\cindex{checksum}
+
+Good algorithms for computing checksums are not
+obvious.  One possibility is to count up the
+number of characters, words, and lines; in the
+UNIX world, this is easily done with the
+\code{wc}\c
+\pindex{wc}\c
+\cindex{word count}
+program.  Another possibility is to just add up
+the numerical values of all the characters and use
+the resulting sum as the checksum.  Both of these
+would change if characters were added or removed,
+but they would not change under transposition of
+characters, words, or lines.\refill
+
+Consequently, a lot of research has been done on
+algorithms for finding checksums, and some have
+even achieved international standardization.  One
+of these standard algorithms is known as a CRC-16
+checksum.  CRC stands for \emph{cyclic redundancy
+checksum},\c
+\cindex{cyclic redundancy checksum}\c
+\cpsubindex{checksum}{cyclic redundancy}
+and the redundancy of following it with
+the word \emph{checksum} is accepted practice.
+The CRC-16 checksum\c
+\cpsubindex{checksum}{CRC-16}
+is capable of detecting error bursts up to 16
+bits, and 99 percent of bursts greater than 16
+bits in length.  The checksum number is
+represented as a 16-bit unsigned number,
+encompassing the range 0 \dots{} 65535.  Thus,
+there is roughly one chance in 65535 of an error
+not being detected, that is, of two different
+files having the same checksum.\refill
+
+Of course, no human should have to compute a
+checksum; that is a job for a computer program.
+The GNU Emacs support software described in this
+document handles the job for you.\refill
+
+We cannot use just any checksum program, however,
+for several reasons:\refill
+\begin{itemize}
+
+\item
+The checksum program must itself be portable and
+freely available, because verification of the
+checksum may be required on any machine that the
+file is transported to.\refill
+
+\item
+File formats change from system to system.  On
+some file systems, text files are represented by
+fixed-length records.  On others, variable
+length records include a count of the number of
+characters in each line.  On still others, lines
+end with character terminator sequences like CR,
+LF, or CR LF.\refill
+
+\item
+The file must contain the checksum, but somehow,
+the checksum itself must not be counted when the
+checksum is computed.  Otherwise, we could never
+achieve self-consistency: each insertion of a new
+checksum would change the checksum.\refill
+
+\item
+Because of the varying line representations in
+file systems, trailing blanks should not be
+included in the checksum.  Such blanks waste
+space, and should never be significant; they can
+be lost when text is refilled in a line-wrapping
+editor, or during electronic mail transmission.
+It is a good idea to get rid of them; the Emacs
+file header maintenance functions described
+elsewhere (\pxref{GNU Emacs editing support})
+do this for you automatically.\refill
+
+\item
+Horizontal tabs\c
+\cindex{tab character}
+look like spaces on the computer
+display, but are really separate characters.
+They are often subject to translation to spaces by
+electronic mail systems.  For most text files, you
+can safely replace them by blanks, which is easy
+to do in Emacs: just mark the whole buffer with
+\kbd{C-x h}, and then type \kbd{M-x untabify}.\refill
+
+UNIX \code{Makefile}s\c
+\pindex{Makefile}
+and \code{troff}\c
+\pindex{troff}
+files are
+notable exceptions to this; tabs are
+\emph{significant} and cannot be replaced without
+destroying the meaning of those files.  That is
+why the GNU Emacs file header maintenance
+functions never touch tabs.\refill
+\end{itemize}
+
+These considerations make it clear than existing
+software for computing checksums just will not do.
+I raised these points in an editorial challenge
+\cite{Beebe:TB11-4-485-487}\c
+\tindex{Beebe, Nelson H. F.}
+in the \TeX{} Users Group\c
+\cindex{TeX Users Group}
+journal, TUGboat,\c
+\cindex{TUGboat}
+and in the spring of 1991 received a clever
+solution from Robert Solovay\c
+\tindex{Solovay, Robert}
+at the University of California,
+Berkeley.\refill
+
+Solovay's program, called simply \code{checksum},\c
+\pindex{checksum}
+is written in a literate programming
+\cindex{literate programming}
+language called CWEB.\c
+\pindex{CWEB}
+The output is C code that conforms
+to the 1989 ANSI/ISO C Standard.  In computing the
+checksum, it ignores line terminators, and any
+previous checksum, and since it has been placed in
+the public domain, it solves all of the problems
+noted above.  Besides a CRC-16 checksum,\c
+\cpsubindex{checksum}{CRC-16}
+it also produces counts of characters, words, and
+lines.  In the event that \code{checksum}\c
+\pindex{checksum}
+has not yet been installed, this information can
+be compared against the output of the UNIX
+\code{wc}\c
+\pindex{wc}\c
+\cindex{word count}
+utility.  \code{wc} is simple enough that it can
+easily be reimplemented on any system.\refill
+
+\code{checksum}\c
+\pindex{checksum}
+also has an option to verify the
+correctness of the checksum in a file;\c
+\cpsubindex{checksum}{validation of}
+you could use this to check for corruption after
+transferring a file with standard file headers to
+your system.\refill
+
+Although \code{checksum}\c
+\pindex{checksum}
+can be run manually, the
+GNU Emacs support code does it for you, producing
+an entry in the file header that looks something
+like this:\refill
+\begin{verbatim}
+%%%     checksum        = "25868 849 3980 28305",
+\end{verbatim}
+
+\noindent
+The four numbers are the CRC-16 checksum,\c
+\cpsubindex{checksum}{CRC-16}
+line count,\c
+\cindex{line count}
+word count,\c
+\cindex{word count}
+and character count.\c
+\cindex{character count}
+You must remember that the character count will
+change if the file is stored with different line
+terminator conventions; the other numbers will
+remain constant.\refill
+
+\node codetable, date, checksum, Attribute descriptions
+
+\section{Codetable}\c
+\cpsubindex{attribute}{codetable}
+
+In the computing world of the 1990s, two major
+character sets are in wide use: EBCDIC\c
+\cindex{EBCDIC character set}\c
+\cpsubindex{character set}{EBCDIC}
+on IBM mainframes and their clones, and
+ISO/ASCII\c
+\cindex{ASCII character set}\c
+\cindex{ISO character set}\c
+\cpsubindex{character set}{ISO}\c
+\cpsubindex{character set}{ASCII}
+on everything else.  EBCDIC is an 8-bit character
+set, offering characters in the range 0 \dots{}
+255, while ISO/ASCII is a 7-bit character set,
+with characters in the range 0 \dots{} 127.  On
+most machines, ISO/ASCII text is stored in 8-bit
+characters.\refill
+
+In turns of numbers of computers, ISO/ASCII is by
+far the most common, since it is the character set
+used by all personal computers and
+workstations.\refill
+
+Unfortunately, a 128-character set with 95
+printable characters and 33 control characters is
+inadequate for most non-English languages.
+Many European languages require accented
+characters or additional letters, and
+Chinese,\c
+\cindex{Chinese characters}
+Japanese,\c
+\cindex{Japanese characters}
+and Korean\c
+\cindex{Korean characters}
+have thousands of pictographic
+characters.\refill\c
+\cpsubindex{character set}{pictographic}
+
+Consequently, computer vendors have dealt with
+this by offering ISO `code pages'\c
+\cpsubindex{character set}{code pages}
+--- variations
+in the encoding of characters 128 \dots{} 255, and
+sometimes even in the encoding of punctuation
+characters in the range 0 \dots{} 127.\refill
+
+Standards bodies are actively working on the
+development of a new character set that will
+support all, or almost all, of the world's present
+and past languages.  One of these efforts is a
+16-bit character set called Unicode,\c
+\cpsubindex{character set}{Unicode}
+and another
+is a 32-bit character set called ISO 10646.\c
+\cpsubindex{character set}{ISO 10646}
+Efforts are now underway to merge these efforts
+into a character set called ISO 10646M (M for
+merged).\refill\c
+\cpsubindex{character set}{ISO 10646M}
+
+Given the speed at which committees work, and the
+enormous impact on millions of computers, and
+people, of a change in text encoding, it seems
+unlikely that the impact of these efforts will be
+felt for another decade.\refill
+
+The code page problem, however, does have to be
+dealt with.  The standard file headers provide for
+this with an attribute entry like\refill
+\begin{verbatim}
+%%%     codetable       = "ISO/ASCII",
+\end{verbatim}
+
+\noindent
+If the file is encoded in, say code page
+ISO-8859-3, then the header could say that:\refill
+\begin{verbatim}
+%%%     codetable       = "ISO-8859-3",
+\end{verbatim}
+
+\noindent
+Of course, if an ASCII file were transferred to a
+system with EBCDIC, the file would not be
+immediately readable until the character values
+were translated to EBCDIC.  The checksum described
+in the preceding section would be incorrect, but
+at least the fact that the file header stated that
+the code was originally ISO/ASCII would explain
+any translation peculiarities that cropped up
+later.\refill
+
+The attribute name \code{codetable}\c
+\cindex{codetable}
+was chosen
+over \code{codepage} because the latter notion is
+restricted to variants of ISO/ASCII.\refill
+
+\node date, docstring, codetable, Attribute descriptions
+
+\section{Date}\c
+\cpsubindex{attribute}{date}
+
+Computer files should always carry a date-and-time\c
+\cindex{time stamp}\c
+\cindex{date stamp}
+stamp to record time of the last modification.
+Some file systems even store date-and-time stamps
+for last read, last write, last backup, and so
+on.\refill
+
+Unfortunately, many computers do not have a
+reliable time standard, and if they lack a network
+connection, have no way of maintaining a correct
+one.  Date-and-time stamps are recorded in the
+file system, rather than the file itself, and are
+usually lost when the file is transferred to
+another system.  That is regrettable, but it is a
+fact of life we still have to tolerate.\refill
+
+Consequently, a standard file header should carry
+a date and time.  The editing support described
+here supplies it in the form\refill
+\begin{verbatim}
+%%%     date            = "07 Oct 1991",
+\end{verbatim}
+
+Dates and times are expressed in a variety of
+formats that depend on the country and culture.\c
+\cpsubindex{date}{cultural dependence}\c
+\cpsubindex{time}{cultural dependence}
+Some software can deal with a considerable variety
+of formats, ranging from ``last Wednesday'' to
+``1991.11.06:12.34.17''.  The important point is
+that the encoding \emph{must be unambiguous}.  In
+particular, forms like \code{12/06/91} should be
+avoided: does it mean the 12th day of the 6th
+month, or the 6th day of the 12th month?  The year
+should \emph{not} be abbreviated to two digits;
+the new millenium is not far away.\refill
+
+\node docstring, email, date, Attribute descriptions
+
+\section{Docstring}\c
+\cpsubindex{attribute}{docstring}
+
+For the purposes of cataloging files, and
+recognizing their contents, it is helpful to have
+a few paragraphs of description.  This is provided
+for by the \code{docstring}\c
+\cindex{docstring}
+attribute, which might
+look like this:\refill
+\begin{verbatim}
+%%%     docstring       = "This LaTeXinfo document describes
+%%%                        filehdr.el, a GNU Emacs support
+%%%                        package for the creation and
+%%%                        maintenance of standard file
+%%%                        headers, such as this one.  It
+%%%                        may be processed by LaTeX to
+%%%                        produce a typeset document, or by
+%%%                        M-x latexinfo-format-buffer in
+%%%                        GNU Emacs to produce an info file
+%%%                        for on-line documentation.
+%%%
+%%%                        The checksum field above contains
+%%%                        a CRC-16 checksum as the first
+%%%                        value, followed by the equivalent
+%%%                        of the standard UNIX wc (word
+%%%                        count) utility output of lines,
+%%%                        words, and characters.  This is
+%%%                        produced by Robert Solovay's
+%%%                        checksum utility.",
+\end{verbatim}
+
+This documentation need not be a user's manual for
+the file, unless the necessary information can be
+communicated in a few paragraphs of no more than a
+couple of thousand characters.  Think of it
+instead as an extended abstract.\refill\c
+\cindex{abstract}\c
+\cpsubindex{documentation string}{as abstract}
+
+Someday, we may have tools that will extract
+documentation strings from standard file headers
+and turn them into catalogs.\refill
+
+\node email, FAX, docstring, Attribute descriptions
+
+\section{Email}\c
+\cpsubindex{attribute}{email}
+
+People who exchange computer files now often have
+network access, and the worldwide Internet is
+growing rapidly.  It will not be long before
+network connections are as commonplace, and
+important, as telephone connections now are.  Most
+networks support electronic mail, and the trend is
+to develop uniform addressing schemes that will
+work the world over.  Thus, an electronic mail\c
+\cindex{electronic mail}
+address, when available, is as important as a
+postal address\c
+\cindex{postal address}
+for the author(s).\refill
+
+Here is an example:\refill
+\begin{verbatim}
+%%%     email           = "beebe@math.utah.edu (Internet)",
+\end{verbatim}
+
+\noindent
+Since there are several networks in existence,
+with different naming conventions, it is helpful
+to identify the network as in this example.\refill
+
+In the event that there are multiple authors,
+electronic mail addresses should be given in the
+same order, separated by the word \code{and}, just
+the way the author attribute value is coded.  Of
+course, not all of the authors might have such an
+address, so additional qualification, such as by a
+parenthesized set of initials, could follow each
+address.  Use your ingenuity, but in such a way
+that someone you've never met will still
+understand what you mean.\refill
+
+\node FAX, filename, email, Attribute descriptions
+
+\section{FAX}\c
+\cpsubindex{attribute}{fax}
+
+The \code{FAX}\c
+\cindex{FAX}
+attribute should be formatted just
+like the \code{telephone}\c
+\cindex{telephone}
+entry.  Here is an
+example:\refill
+\begin{verbatim}
+%%%     FAX             = "+1 801 581 4148",
+\end{verbatim}
+
+FAX machines are now very commonly used in
+business throughout the world, so if you have such
+a facility, it is a good idea to include it in the
+file header.\refill
+
+\node filename, keywords, FAX, Attribute descriptions
+
+\section{Filename}\c
+\cpsubindex{attribute}{filename}
+
+Different computing systems have different file
+naming conventions; in particular, there are
+significant variations in the naming of files.
+Some systems, like the Apple Macintosh, permit
+arbitrary strings of characters, including blanks.
+Others, like MS DOS on the IBM PC and clones,
+limit names to two parts, a base name and an
+extension, or type, with the two separated by a
+period (dot, full stop).\refill
+
+File headers should therefore carry an indication
+of the original name of the file, and if the file
+is expected to be referenced by other files, then
+it is \emph{imperative} that the name chosen be
+representable on a wide variety of, and preferably
+all, computing systems.  Today, this in practice
+means the 8-character base name and 3-character
+file extension of MS DOS, which runs in tens of
+millions of personal computers.\c
+\cpsubindex{filename}{portable subset}
+There are still a few survivors of older operating
+systems with more stringent requirements on file
+names, but they are obsolete and rapidly
+disappearing.\refill
+
+The filename should be case \emph{insensitive},\c
+\cpsubindex{filename}{case insensitivity}
+and in the header, spelled in lower-case letters.
+It should start with a letter, and use only
+letters, digits, and perhaps, hyphens (minus
+signs) in the rest of the name, with no more than
+a single period in the name.\refill\c
+\cpsubindex{filename}{characters allowed in}
+
+This document's file header contains the attribute
+entry\refill
+\begin{verbatim}
+%%%     filename        = "filehdr.ltx",
+\end{verbatim}
+
+\noindent
+\code{filehdr} is an abbreviation for ``file
+header'', and \code{ltx} for ``\LaTeX{}'',\c
+\cindex{LaTeX}
+the name of the document formatting system that
+typesets this document.\refill
+
+\node keywords, supported, filename, Attribute descriptions
+
+\section{Keywords}\c
+\cpsubindex{attribute}{keywords}
+
+Large archives always pose a search problem for
+human users, and it has long been traditional to
+try to classify members of the archives by
+\emph{keywords} that might come to mind when
+someone is searching for the file.  Some journals
+have standard sets of keywords to classify
+articles by, and include them near the abstract of
+each paper.\refill
+
+With standard file headers, the range of possible
+keywords is enormous, and authors will just have
+to be diligent about finding good sets of
+descriptive keywords.  They should appear in the
+attribute value as phrases separated by commas, as
+for this document:\refill
+\begin{verbatim}
+%%%     keywords        = "file header, checksum",
+\end{verbatim}
+
+\node supported, telephone, keywords, Attribute descriptions
+
+\section{Supported}\c
+\cpsubindex{attribute}{supported}
+
+All computer files reach a stage of stagnation,
+where for various reasons, their authors no longer
+maintain them.  Nevertheless, it is helpful to
+know whether the author of a given file is
+interested in hearing of problems or comments, and
+the file header can say so by an entry like this
+one:\refill
+\begin{verbatim}
+%%%     supported       = "yes",
+\end{verbatim}
+
+If it says \code{yes}, this does not provide any
+guarantee that any problems reported will be
+fixed, but just that the author's intentions are
+good, and reasonable efforts will be made to do
+so.  Some authors even care so much about their
+work that they offer monetary rewards for reports
+of bugs and errors.\refill
+
+If it says \code{no}, then you are on your own,
+because the author never wants to hear from you on
+the subject of this particular file.\refill
+
+Other attribute values can be readily imagined,
+like \code{only for money, cash in advance}, but a
+simple \code{yes} or \code{no} is probably
+adequate for most people.\refill
+
+\node telephone, time, supported, Attribute descriptions
+
+\section{Telephone}\c
+\cpsubindex{attribute}{telephone}
+
+The \code{telephone}\c
+\cindex{telephone}
+attribute should include the
+area code with telephone number.  If there are
+multiple values, separate them by commas.  Here is
+an example from the file header of this document:\refill
+\begin{verbatim}
+%%%     telephone       = "+1 801 581 5254",
+\end{verbatim}
+Use the international form of the number,
+including the country and city\slash area code.
+
+\node time, version, telephone, Attribute descriptions
+
+\section{Time}\c
+\cpsubindex{attribute}{time}
+
+The \code{time}\c
+\cindex{time}
+attribute should be of the form
+\code{hh:mm:ss}, or if a time zone abbreviation
+(say, \code{GMT}) can be found, \code{hh:mm:ss
+GMT}.  It is recorded separately from the
+\code{date}\c
+\cindex{date}
+to ease the parsing job of software
+that processes file headers.\refill
+
+Here is a typical example:\refill
+\begin{verbatim}
+%%%     time            = "18:02:38 MST",
+\end{verbatim}
+
+\node version, multiple values, time, Attribute descriptions
+
+\section{URL}\c
+\cpsubindex{attribute}{URL}
+
+Since its introduction in the early 1990s, the
+WorldWide Web has spread rapidly, so that most
+public interest in the Internet is associated with
+it, and so that most Internet sites that
+previously had electronic mail, ftp, and telnet
+services, now also have a WorldWide Web presence.\refill
+
+The Uniform Resource Locator, or URL, is therefore
+a suitable addition to the standard file headers;
+the one in this file looks like this:\refill
+\begin{verbatim}
+%%%     URL             = "http://www.math.utah.edu/~beebe",
+\end{verbatim}
+
+Since most sites have found it convenient to name
+a particular machine with the prefix ``www.'',
+from an electronic mail address one can often
+guess what the corresponding URL should be.
+Nevertheless, the host with that name is often
+different from the login host, so the Emacs code
+in \file{filehdr.el} may not successfully identify
+it automatically. Thus, you can provide an
+overriding private definition like this in your
+\file{.emacs} startup file:\refill
+\begin{verbatim}
+(setq file-header-user-URL "http://www.math.utah.edu/~beebe")
+\end{verbatim}
+\vindex{file-header-user-URL}
+
+
+\section{Version}\c
+\cpsubindex{attribute}{version}
+
+Computer files created by humans almost inevitably
+go through many revisions, whether they are
+programs to control a satellite, or just the words
+of a promotion for the latest soap product.\refill
+
+Computer vendors have long dealt with this by
+attaching \emph{version numbers}\c
+\cindex{version number}
+to software releases.  These consist of two or
+three numbers with some separator character, such
+as a period (full stop, dot).  The first number is
+called the \emph{major version number}; it gets
+changed only at long intervals, usually years,
+when really significant changes have been
+incorporated.  A second number is a \emph{minor
+version number} which is incremented as smaller
+changes and bug fixes are incorporated.  Sometimes
+a third number is appended, which is an \emph{edit
+number}; it gets incremented every time any change
+at all is made to the file.\refill
+
+In careful software production, a change log\c
+\cindex{change log}
+is kept to record the reasons for every change;
+this is particularly important when commercial
+interests or legal issues are at stake.  [Military
+organizations the world over are famous for their
+paperwork trails; perhaps that is what helps to
+keep them busy during times of peace.]\refill
+
+For smaller files, you can probably get by with
+just a major version number and an edit number;
+for larger projects, three or more are
+recommended.\refill
+
+Here is what one version of this document had in
+its standard file header:\refill
+\begin{verbatim}
+%%%     version         = "1.01",
+\end{verbatim}
+
+Version numbers are particularly useful when
+reporting problems to the author of a file; they
+allow rapid verification of whether the author and
+end user are even talking about the same
+thing.\refill
+
+\node multiple values, Attribute descriptions, version, Attribute descriptions
+
+\section{Multiple values}\c
+\cpsubindex{attribute}{multiple values}
+
+Keywords like \code{author}\c
+\cindex{author}
+and \code{address}\c
+\cindex{address}
+may be inadequate for files prepared by more than
+one person.  If several authors share a common
+address, then using the keyword \code{and},\c
+\cindex{and}
+to separate names in the \code{author}\c
+\cindex{author}
+field is unambiguous.  However, if the postal
+address, electronic mail address, telephone
+number, and FAX number vary, it is advisable to
+clarify the header by attaching a hyphen and a
+numeric suffix to the attribute name.  Here is an
+example:\refill
+\begin{verbatim}
+%%%     author-1        = "Marie Claire LeBrun",
+%%%     author-2        = "Hans Peter Brun",
+%%%     author-3        = "Jill Brown",
+%%%     address-1       = "...",
+%%%     address-2       = "...",
+%%%     address-3       = "...",
+%%%     email-1         = "...",
+%%%     email-2         = "...",
+%%%     email-3         = "...",
+%%%     telephone-1     = "...",
+%%%     telephone-2     = "...",
+%%%     telephone-3     = "...",
+%%%     FAX             = "...",
+\end{verbatim}
+
+File-header parsing software must be prepared to
+handle numeric suffixes like this for any keyword.
+If a keyword doesn't have such a suffix, as the
+\code{FAX}\c
+\cindex{FAX}
+keyword in this example, then it should be assumed
+to apply to all authors.\refill
+
+\node GNU Emacs editing support, Simple customization, Attribute descriptions, Top
+
+\chapter{GNU Emacs editing support}\c
+\cindex{editing support}\c
+\cindex{Emacs editing support}\c
+\cindex{GNU Emacs editing support}
+
+The preceding chapters have outlined the
+background for, and contents of, standard file
+headers.  Here we show how to generate them with
+very little effort.\refill
+
+The GNU Emacs file
+\file{filehdr.el} contains the following
+user-callable functions:\refill
+\begin{verbatim}
+make-file-header
+show-file-header-variables
+test-file-header
+update-checksum
+update-date
+update-date-and-minor-version
+update-file-header-and-save
+update-major-version
+update-minor-version
+update-simple-checksum
+\end{verbatim}
+
+There are several other functions in that file,
+but they are for internal use only, and will not
+be further documented here.\refill
+
+When you want to add a new file header to an
+existing file, you just type \kbd{M-x
+make-file-header}; this produces something like
+this at the top of your file:\refill
+\begin{verbatim}
+%%% ====================================================================
+%%%  @LaTeX-file{
+%%%     author          = "Nelson H. F. Beebe",
+%%%     version         = "1.28",
+%%%     date            = "06 March 1996",
+%%%     time            = "13:14:03 MST",
+%%%     filename        = "filehdr.ltx",
+%%%     address         = "Center for Scientific Computing
+%%%                        Department of Mathematics
+%%%                        University of Utah
+%%%                        Salt Lake City, UT 84112
+%%%                        USA",
+%%%     telephone       = "+1 801 581 5254",
+%%%     FAX             = "+1 801 581 4148",
+%%%     URL             = "http://www.math.utah.edu/~beebe",
+%%%     checksum        = "53883 2543 10843 81774",
+%%%     email           = "beebe@math.utah.edu (Internet)",
+%%%     codetable       = "ISO/ASCII",
+%%%     keywords        = "file header, checksum",
+%%%     supported       = "yes",
+%%%     docstring       = "This LaTeXinfo document describes
+%%%                        filehdr.el, a GNU Emacs support package for
+%%%                        the creation and maintenance of standard
+%%%                        file headers, such as this one.  It may be
+%%%                        processed by LaTeX to produce a typeset
+%%%                        document, or by M-x latexinfo-format-buffer
+%%%                        in GNU Emacs to produce an info file for
+%%%                        on-line documentation.
+%%%
+%%%                        The checksum field above contains a CRC-16
+%%%                        checksum as the first value, followed by the
+%%%                        equivalent of the standard UNIX wc (word
+%%%                        count) utility output of lines, words, and
+%%%                        characters.  This is produced by Robert
+%%%                        Solovay's checksum utility.",
+%%%  }
+%%% ====================================================================
+\end{verbatim}
+
+\noindent
+Where does it get all of this information?  Well,
+the file name, date and time stamps, author name,
+electronic mail address, and date are all
+determined automatically from calls to various
+system services.  For example, on UNIX, the author
+name comes from the file \file{/etc/passwd}; on
+VAX VMS, it will come from the file
+\file{SYS$MANAGER:SYSUAF.DAT}.\refill
+
+The comment syntax was determined from the file
+extension, and we'll say more about it
+later.\refill
+
+The only information above that Emacs cannot
+determine is your postal address,\c
+\cpsubindex{postal address}{defining}
+and telephone\c
+\cpsubindex{telephone number}{defining}
+and FAX numbers, and possibly,  your WorldWide Web
+URL.\c
+\cpsubindex{FAX number}{defining}
+These only have to be supplied once, usually in
+your GNU Emacs startup file, \file{.emacs}.  This
+is most easily done with Lisp code that looks
+something like this:\refill
+\begin{verbatim}
+(setq file-header-user-address  ; for M-x make-file-header
+  "Center for Scientific Computing
+Department of Mathematics
+University of Utah
+Salt Lake City, UT 84112
+USA")
+
+(setq file-header-user-telephone "+1 801 581 5254")
+
+(setq file-header-user-FAX "+1 801 581 4148")
+
+(setq file-header-user-URL "http://www.math.utah.edu/~beebe")
+\end{verbatim}
+\vindex{file-header-user-address}\c
+\vindex{file-header-user-telephone}\c
+\vindex{file-header-user-FAX}
+\vindex{file-header-user-URL}
+
+Once this is installed in the \file{.emacs} file,
+GNU Emacs will find it every time it starts up.\refill
+
+If the electronic-mail address constructed from
+the Emacs
+\code{user-login-name}\c
+\findex{user-login-name}
+and
+\code{system-name}\c
+\findex{system-name}
+functions is not suitable, you can provide an
+alternative one like this:\refill
+\begin{verbatim}
+(setq file-header-user-email "beebe@math.utah.edu")
+\end{verbatim}
+\vindex{file-header-user-email}\c
+
+\noindent
+In any of the following situations, you
+should set \code{file-header-user-email}\c
+\vindex{file-header-user-email}
+in your startup \file{.emacs} file.\refill
+\begin{itemize}
+
+\item
+You work on multiple machines, but prefer to have
+only one public electronic-mail address.\refill
+
+\item
+At some sites, \code{system-name}\c
+\findex{system-name}
+does not return a fully-qualified Internet host
+name, so the default address constructed by
+\code{file-header-email}\c
+\findex{file-header-email}
+is unusable outside your local
+installation.\refill
+
+\item
+Your site is not on the Internet, but you can
+receive electronic mail via some other
+network.\refill
+\end{itemize}
+
+The version number is left empty; you can manually
+insert an appropriate one, perhaps 1.00, or if you
+are just starting, 0.00.\refill
+
+The checksum and keywords entries are also left
+empty.  There is no point in inserting a checksum
+until you are ready to save the file, and the
+keywords have to be supplied by a human.\refill
+
+Now suppose you've just edited a file with such a
+file header, and you would like to update the
+header to reflect the changes, and then save the
+file.  All you need to type is \kbd{M-x
+update-file-header-and-save}, and with Emacs'
+normal command completion, you can probably hit
+the tab key after the \kbd{f} in \kbd{file}.\refill
+
+The function \code{update-file-header-and-save}\c
+\findex{update-file-header-and-save}
+will update the date and time stamps, the minor
+version number, the checksum, and save the
+file.\refill
+
+If the file is a \LaTeX{}\c
+\cpsubindex{LaTeX}{date update}
+file, the date update
+will also search forward for text that looks
+something like\refill
+\begin{verbatim}
+\\date{29 November 1991 \\
+Version 1.01}
+\end{verbatim}
+
+\noindent
+and change it to the current date and version.
+That makes it easy to get the version number and
+revision date printed on the title page.\refill
+
+You can do these updates manually if you like by
+invoking the functions
+\code{update-checksum},\c
+\findex{update-checksum}
+\code{update-date},\c
+\findex{update-date}
+\code{update-minor-version},\c
+\findex{update-minor-version}
+and
+\code{update-date-and-minor-version}\c
+\findex{update-date-and-minor-version}
+explicitly.\refill
+
+Major version numbers are rarely changed, and you
+could easily do the job manually.  Nevertheless,
+for completeness, \code{update-major-version}\c
+\findex{update-major-version}
+is supplied to automate the job.\refill
+
+\code{update-checksum}\c
+\findex{update-checksum}
+will trim trailing
+whitespace\c
+\cpsubindex{whitespace}{discarding trailing}
+(but leave embedded tabs intact), send the buffer
+to the \file{checksum} program, and replace it
+with the output.  Don't interrupt it while it is
+working, or you might lose your file!\refill
+\typeout{Check interruption of update-checksum;
+maybe use save-for-undo}\c
+\typeout{Maybe should have man pages for checksum
+in an appendix?}\c
+
+The Emacs interface to \file{checksum} has not yet
+been tested on VAX VMS,\c
+\cindex{VAX VMS}
+so
+\code{update-checksum}\c
+\findex{update-checksum}
+on that system calls
+\code{update-simple-checksum}\c
+\findex{update-simple-checksum}
+instead.  That
+function will compute counts of lines, words, and
+characters and insert them in the checksum value.
+You could use this if for some reason you don't
+have \code{checksum}\c
+\pindex{checksum}
+installed yet.
+\code{checksum} should be available from the same
+place you got \file{filehdr.el}; eventually it
+will be on dozens of \TeX{} archive machines
+around the world.\refill
+
+\node Simple customization, Advanced customization, GNU Emacs editing support, Top
+
+\chapter{Simple customization}\c
+\cpsubindex{customization}{simple}
+
+The GNU Emacs Lisp code in \file{filehdr.el} has
+been written to make it easy to customize without
+your having to become a Lisp programmer.  Of
+course, Lisp is so much fun that you might want to
+do that anyway!\refill
+
+The code contains several large tables stored in Lisp
+variables:\refill
+\begin{verbatim}
+file-header-standard-at-sign-special-cases
+file-header-standard-comment-prefixes
+file-header-standard-entries
+file-header-standard-paired-comment-delimiter-languages
+file-header-standard-suffix-and-type
+\end{verbatim}
+
+\noindent
+These are not intended to be modified by users, as
+the phrase \code{-standard-} in their names
+indicates.\refill
+
+Each of them is a list of lists; the innermost
+lists contain two or three character strings.
+Sublists are ordered alphabetically for human
+readability; the code does not care what order
+they appear in.\refill
+
+The first of them,
+\code{file-header-standard-at-sign-special-cases},\c
+\vindex{file-header-standard-at-sign-special-cases}
+is used to handle those few exceptional file
+classes that do not permit at-signs, \code{@}, to
+be used in comments without special handling.
+Here is the current value of this variable:\refill
+\begin{verbatim}
+(
+    ("BibTeX"               " at ")
+    ("C-Web"                "@@")
+    ("Web"                  "@@")
+    ("Web-change"           "@@")
+)
+\end{verbatim}
+
+\noindent
+This means that when a header for a file in class
+\samp{BibTeX} is created, at-signs should be
+replaced by the string \samp{ at }.  For the other
+classes, at-signs must be doubled.\refill
+
+The second variable,
+\code{file-header-standard-comment-prefixes},\c
+\vindex{file-header-standard-comment-prefixes}
+has
+a very long value, so we show only a portion
+here:\refill
+\begin{verbatim}
+(
+    ("Adobe-Font-Metric"    "Comment ")
+    ("AmSTeX"               "%%% ")
+    ("Awk"                  "### ")
+...
+    ("Web-change"           "%%% ")
+    ("Yacc"                 "")
+)
+\end{verbatim}
+
+\noindent
+This means that in an Adobe Font Metric file,\c
+\cindex{Adobe Font Metric file}
+comments must begin a line with the string
+\samp{Comment }.  For \code{awk}\c
+\pindex{awk}
+files, a triple
+sharp sign and a space will begin all file header
+lines.  \code{yacc}\c
+\pindex{yacc}
+file headers have no comment
+prefix at all.\refill
+
+The third variable,
+\code{file-header-standard-entries},\c
+\vindex{file-header-standard-entries}
+contains pairs of entry names and functions to
+supply values for them.  It looks something like
+this: \refill
+\begin{verbatim}
+(
+ ("author"       file-header-author)
+ ("version"      file-header-version)
+ ("date"         file-header-date)
+ ("time"         file-header-time)
+ ("filename"     file-header-filename)
+ ("address"      file-header-address)
+ ("telephone"    file-header-telephone)
+ ("FAX"          file-header-FAX)
+ ("URL"          file-header-URL)
+ ("checksum"     file-header-checksum)
+ ("email"        file-header-email)
+ ("codetable"    file-header-codetable)
+ ("keywords"     file-header-keywords)
+ ("supported"    file-header-supported)
+ ("docstring"    file-header-docstring)
+)
+\end{verbatim}
+
+\noindent
+The file header is created by processing these
+entry names in order.\refill
+
+The fourth variable, with the name
+\code{file-header-standard-paired-comment-delimiter-languages},\c
+\vindex{file-header-standard-paired-comment-delimiter-languages}
+is a little more complex.  Its classes cover
+languages that use distinct starting and ending
+comment strings, instead of having comments that
+terminate at end of line.  For each class name,
+its list entries contain two strings, one for
+the comment start, and one for the comment end.
+To help make them stand out better, the strings
+are often stretched to 72 characters in
+length:\refill
+\begin{verbatim}
+(
+    ("C"
+     (concat "/*"  (make-string 70 ?\*) "\n")
+     (concat (make-string 70 ?\*) "*/\n"))
+
+    ("Font-Property-List"
+      (concat "(COMMENT "(make-string 63 ?\*) "\n")
+      (concat (make-string 71 ?\*) ")\n"))
+...
+    ("Scribe"
+      "@Begin{Comment}\n"
+      "@End{Comment}\n")
+...
+    ("Yacc"
+     (concat " /*" (make-string 69 ?\*) "\n")
+     (concat " " (make-string 69 ?\*) "*/\n"))
+    )
+)
+\end{verbatim}
+
+\noindent
+To avoid the need for long constant strings in the
+code, several of them are generated dynamically
+by the Lisp concatenation operator,
+\code{concat}.\refill\c
+\findex{concat}
+
+Class names in this variable do \emph{not} include
+the phrase \code{-file} that appears in the file
+header; that suffix is supplied automatically by
+the Emacs functions.\refill
+
+The last variable,
+\code{file-header-standard-suffix-and-type},\c
+\vindex{file-header-standard-suffix-and-type}
+is the biggest of them all.  It relates file
+extensions to file classes.  This indirection was
+chosen because there are often several file
+extensions belonging to a single class.  Its value
+looks something like this:\refill
+\begin{verbatim}
+(
+    ("1"            "Troff-man")
+    ("1l"           "Troff-man")
+    ("2"            "Troff-man")
+...
+    ("afm"          "Adobe-Font-Metric")
+...
+    ("web"          "Web")
+    ("y"            "Yacc")
+    ("yacc"         "Yacc")
+)
+\end{verbatim}
+
+\noindent
+Observe that the extensions do \emph{not} include
+a leading period.\refill
+
+The list of extensions was constructed by going
+through some large UNIX file systems (several
+hundred thousand files) to produce a set of unique
+file extensions, and then augmenting the list by
+hand based on the author's personal experience on
+several other operating systems.  The resulting
+list has about 150 file extensions, and 85 file
+classes.  If a file extension is unrecognized, it
+is assigned the class name \code{UNKNOWN}.\refill
+
+Here now is how you can customize the behavior of
+\code{make-file-header}.\c
+\findex{make-file-header}
+For each Lisp variable with
+the phrase \code{-standard-}, there is a
+corresponding one with the phrase \code{-extra-}
+instead.  These new variables are intended for
+user customization; you can initialize them in
+your startup \file{.emacs} file, and they will
+automatically be added to the standard ones at run
+time.\refill
+
+Here is a set of sample customizations:\refill\c
+\cpsubindex{customization}{examples}
+\begin{verbatim}
+(setq file-header-extra-at-sign-special-cases
+      '(
+        ("Foo-Bar"      " <<<AT>>> ")
+        ))
+
+(setq file-header-extra-comment-prefixes
+      '(
+        ("Foo-Bar"      "!FB!")
+        ))
+
+(setq file-header-extra-entries
+      '(
+        ("copyright"    file-header-copyright)
+        ))
+
+(setq file-header-extra-suffix-and-type
+      '(
+        ("foobar"       "Foo-Bar")
+       ))
+
+(setq file-header-extra-paired-comment-delimiter-languages
+      '(
+        ("Foo-Bar"
+         (concat "/#"  (make-string 70 ?\#) "\n")
+         (concat (make-string 70 ?\#) "#/\n"))
+        ))
+\end{verbatim}
+\vindex{file-header-extra-at-sign-special-cases}\c
+\vindex{file-header-extra-comment-prefixes}\c
+\vindex{file-header-extra-entries}\c
+\vindex{file-header-extra-suffix-and-type}\c
+\vindex{file-header-extra-paired-comment-delimiter-languages}\c
+
+\noindent
+These would define a new file class \code{Foo-Bar}
+attached to files with extension \code{.foobar},
+for which comments are delimited by \code{/# \dots{} #/},
+and by \code{!} to end-of-line.  The file header body
+lines would all begin with \code{!FB!}.\refill
+
+The Lisp form \code{(setq var value)}\c
+\findex{setq}
+assigns \code{value} to the variable \code{var}; most
+other programming languages would write this as
+\code{var = value}.\refill
+
+The extra values set in these variables are
+appended to the end of the standard ones, so they
+can augment, \emph{but not replace}, the standard
+values.  This design choice was made intentionally
+to encourage \emph{standardization} of the file
+headers.  If you need to do something differently,
+you'll have to learn some Lisp, and look in the
+next chapter.\refill
+
+You can test your additions by visiting
+files with the new extensions, and then running
+\kbd{M-x make-file-header}.\refill\c
+\findex{make-file-header}
+
+You can test the entire collection of code by
+typing \kbd{M-x test-file-header}.\c
+\findex{test-file-header}
+This takes a while, but is thorough: it will
+create file headers in a temporary editor buffer
+for every file extension defined in the two lists
+\code{file-header-standard-suffix-and-type}\c
+\vindex{file-header-standard-suffix-and-type}
+and
+\code{file-header-extra-suffix-and-type}.\refill\c
+\vindex{file-header-extra-suffix-and-type}
+
+To see the settings of the variables named
+\code{file-header-standard-xxx}\c
+\vindex{file-header-standard-xxx}
+and
+\code{file-header-extra-xxx},\c
+\vindex{file-header-extra-xxx}
+type
+\kbd{M-x show-file-header-variables}.\c
+\findex{show-file-header-variables}
+The results will appear in a temporary
+buffer.\refill
+
+Prior to version 19 (released in early summer of
+1993), GNU Emacs did not provide the time zone,\c
+\cindex{time zone}
+but on UNIX systems, it can
+be obtained from the output of the \code{date}\c
+\pindex{date}
+command.  Since this takes a few seconds to run as
+a subprocess, the result is saved in a global
+variable, \code{file-header-timezone-string}.\c
+\vindex{file-header-timezone-string}
+Subsequent file headers will be produced much more
+rapidly.  With Version 19 or later, this delay is
+eliminated.
+\refill
+
+If you find the delay on the first use
+objectionable, you can set the time zone in your
+\file{.emacs} file:\refill
+\begin{verbatim}
+(setq file-header-timezone-string "MST")
+\end{verbatim}
+
+\noindent
+This practice is not recommended, since you'll
+have to change it twice a year, or if you work in
+a different time zone.\refill
+
+\node Advanced customization, Bug reporting, Simple customization, Top
+
+\chapter{Advanced customization}\c
+\cpsubindex{customization}{advanced}
+
+What do you do if you want to insert additional
+fields in all new file headers?  You have to do
+some Lisp programming to add to the
+functions in \file{filehdr.el}.  \emph{Under no
+circumstances should you modify \file{filehdr.el}
+itself!}  That is the sole prerogative of its
+original author.  You can freely copy code from
+it, but put that code in a file with a different
+name.\refill
+
+If you are a real Lisp wizard, you can just read
+the code in \file{filehdr.el}, and write whatever
+new code you want.  On the other hand, if you were
+such a wizard, you'd probably ``read the code
+instead of this documentation.''\refill
+
+The most likely function you'll want to modify is
+\code{make-file-header}.\c
+\findex{make-file-header}
+Here is what its body
+looks like:\refill
+\begin{verbatim}
+    (file-header-comment-block-begin)
+    (file-header-entry)
+    (mapcar '(lambda (entry)
+               (file-header-key (car entry) (nth 1 entry)))
+            (append file-header-standard-entries
+                    file-header-extra-entries))
+    (file-header-exit)
+    (file-header-comment-block-end)
+\end{verbatim}
+\vindex{file-header-standard-entries}\c
+\vindex{file-header-extra-entries}\c
+\findex{file-header-comment-block-begin}\c
+\findex{file-header-entry}\c
+\findex{lambda}\c
+\findex{mapcar}\c
+\findex{append}\c
+\findex{file-header-key}\c
+\findex{car}\c
+\findex{nth}\c
+\findex{file-header-exit}\c
+\findex{file-header-comment-block-end}\c
+
+\noindent
+Each of these lines is a Lisp function call; the
+function name is the first one in each
+parenthesized list.  Each function supplies part
+of the standard file header.\refill
+
+The first and last function calls provide a full
+line comment start and end, if the file class
+requires it.\refill
+
+The \code{file-header-entry}\c
+\findex{file-header-entry}
+and \code{file-header-exit}\c
+\findex{file-header-exit}
+functions supply the class name tag and the final
+closing brace.  That is, they generate something
+like this:\refill
+\begin{verbatim}
+%%%  @LaTeX-file{
+%%%  }
+\end{verbatim}
+
+\noindent
+The individual file attributes are then supplied
+by calls to the generic function
+\code{file-header-key},\c
+\findex{file-header-key}
+which is given the
+attribute name as its first argument, and the name
+of a function to call to generate a string for the
+attribute's initial value.  The returned string
+may span multiple lines; it will be neatly
+formatted and properly indented by a service
+function called inside
+\code{file-header-key}.\refill
+
+The Lisp \code{mapcar}\c
+\findex{mapcar}
+function called in the body
+of \code{make-file-header}\c
+\findex{make-file-header}
+applies its second argument, here an anonymous
+\code{lambda}\c
+\findex{lambda}
+function, to each element of the list supplied as
+its third argument.  The keywords that are
+inserted are determined by the entries in the
+lists \code{file-header-standard-entries}\c
+\vindex{file-header-standard-entries}
+and
+\code{file-header-extra-entries},\c
+\vindex{file-header-extra-entries}
+which are
+appended into one big list.\refill
+
+Here is a simple example of one of these
+initial value-returning functions:\refill
+\begin{verbatim}
+(defun file-header-codetable ()
+  "Return as a string the default codetable value."
+  "ISO/ASCII"
+  )
+\end{verbatim}
+
+If you want to add a new file header attribute
+entry, you need to add an entry to
+\code{file-header-extra-entries},\c
+\vindex{file-header-extra-entries}
+and write a
+function to return an appropriate initial
+value.\refill
+
+This is best illustrated by a real example---the
+addition of a copyright attribute\c
+\cpsubindex{attribute}{copyright}
+in the file header.\refill
+
+First we insert the lines\refill
+\begin{verbatim}
+(setq file-header-extra-entries
+      '(
+        ("copyright" file-header-copyright)
+        ))
+\end{verbatim}
+
+\noindent
+in the \file{.emacs} file.\refill
+
+Next, we write the function to return the initial
+value:\refill
+\begin{verbatim}
+(defun file-header-copyright ()
+  "Return as a string the default copyright value."
+  "None.  This file is PUBLIC DOMAIN."
+)
+\end{verbatim}
+
+That is all there is to it.  To test the new code,
+you can compile it inside Emacs in Emacs-Lisp
+editing mode by typing \kbd{ESC C-x} with the
+cursor inside the function, and then run it by
+name from the minibuffer:
+\kbd{ESC ESC (file-header-copyright)}.\refill
+
+When you run \code{make-file-header},\c
+\findex{make-file-header}
+it should now produce an attribute entry
+like\refill
+\begin{verbatim}
+%%%     copyright     = "None.  This file is PUBLIC DOMAIN.",
+\end{verbatim}
+
+When everything is working, save the new Emacs
+Lisp file, and run \kbd{M-x byte-compile-file} on
+it.  You can then load it interactively with
+\kbd{M-x load-file}, or better, automatically at
+Emacs start-up time by adding the line\refill
+\begin{verbatim}
+(load "myfilhdr" t t nil)
+\end{verbatim}
+
+\noindent
+assuming you called the modified file \file{myfilhdr.el}.\refill
+
+If the code in \file{myfilhdr.el} is short, you
+can keep it in your \file{.emacs} instead, and
+altogether avoid the need for a separate file and
+the byte compilation and \code{load}\c
+\findex{load}
+command.
+Compilation is only useful for speeding up the
+loading of large files of Emacs Lisp code.\refill
+
+You probably will not have to do any more than
+this, unless you add a new attribute that must be
+updated each time the function
+\code{update-file-header-and-save}\c
+\findex{update-file-header-and-save}
+is invoked.  In
+such a case, you'll have to study its body, and
+the functions it calls, to make the necessary
+modifications.\refill
+
+\node Bug reporting, Bibliography, Advanced customization, Top
+
+\chapter{Bug reporting}\c
+\cindex{bug reporting}
+
+Bug reports, and comments, are actively solicited.
+Electronic mail to the author is most convenient,
+but postal mail, preferably accompanied by
+machine-readable material on Apple Macintosh or
+IBM PC floppy disks, are also acceptable.  Shorter
+communications via FAX are also possible.  Here
+are the necessary addresses and telephone numbers:\refill
+
+\begin{verbatim}
+Nelson H. F. Beebe
+Center for Scientific Computing
+Department of Mathematics
+University of Utah
+Salt Lake City, UT 84112
+USA
+Tel: +1 801 581 5254
+FAX: +1 801 581 4148
+Email: beebe@math.utah.edu
+URL: http://www.math.utah.edu/~beebe
+\end{verbatim}
+
+\node Bibliography, Concept Index, Bug Reporting, Top
+
+\begin{ifinfo}
+\begin{description}
+\item[Beebe:TB11-4-485-487]
+Nelson H. F. Beebe.
+{{From the President}}.
+\emph{TUGboat}, 11(4):485--487, November
+1990.\refill
+
+\item[Lamport:LDP85]
+Leslie Lamport.
+\emph{{\LaTeX}---A Document Preparation
+System---User's Guide and Reference Manual}.
+Ad{\-d}i{\-s}on-Wes{\-l}ey, 1985.\refill
+
+\item[Lottor:CACM-34-11-21]
+Mark Lottor.
+Internet domain system.
+\emph{Communications of the Association for Computing Machinery},
+34(11):21--22, November 1991.\refill
+This letter reports that the ZONE program at the
+Network Information Systems Center at SRI
+International in July 1991 found approximately
+535,000 Internet hosts in 16,000 domains. The 10
+largest domains were EDU (educational)--206,000,
+COM (commercial)--144,000, GOV
+(government)---36,000, MIL (military) 26,000, AU
+(Australia)--22,000, DE (Germany)---21,000, CA
+(Canada)--19,000, ORG (organizations)---15,000, SE
+(Sweden)---12,000, and CH
+(Switzerland)---10,000.\refill
+
+\item[Unilogic:SDP84]
+Unilogic, Ltd.
+\emph{Scribe Document Production System User
+Manual}, April 1984.\refill
+\end{description}
+\end{ifinfo}
+
+\begin{iftex}
+\bibliography{filehdr}
+\end{iftex}
+
+\onecolumn
+
+\node Concept index, Function index, Bibliography, Top
+
+\begin{ifinfo}
+\chapter*{Concept index}
+\end{ifinfo}
+\begin{iftex}
+\unnumbered{Concept index}
+\end{iftex}
+\cindex{concept index}
+\cpsubindex{index}{concept}
+\printindex{cp}
+
+\onecolumn
+\node Function index, Person index, Concept index, Top
+
+\begin{ifinfo}
+\chapter*{Function index}
+\end{ifinfo}
+\begin{iftex}
+\unnumbered{Function index}
+\end{iftex}
+\cindex{function index}
+\cpsubindex{index}{function}
+\printindex{fn}
+
+\onecolumn
+\node Person index, Program index, Function index, Top
+
+\begin{ifinfo}
+\chapter*{Person index}
+\end{ifinfo}
+\begin{iftex}
+\unnumbered{Person index}
+\end{iftex}
+\cindex{person index}
+\cpsubindex{index}{person}
+\printindex{tp}
+
+\onecolumn
+\node Program index, Variable index, Person index, Top
+
+\begin{ifinfo}
+\chapter*{Program index}
+\end{ifinfo}
+\begin{iftex}
+\unnumbered{Program index}
+\end{iftex}
+\cindex{program index}
+\cpsubindex{index}{program}
+\printindex{pg}
+
+\onecolumn
+\node Variable index, Top, Program index, Top
+
+\begin{ifinfo}
+\chapter*{Variable index}
+\end{ifinfo}
+\begin{iftex}
+\unnumbered{Variable index}
+\end{iftex}
+\cindex{variable index}
+\cpsubindex{index}{variable}
+\printindex{vr}
+
+\end{document}
+%%% This is for GNU Emacs file-specific customization:
+%%% Local Variables:
+%%% fill-column: 50
+%%% End: