
\title{A \LaTeX\ Tour: Part 1}
\author[David Carlisle]{David Carlisle}
%                        Mathematics Department\\
%                        Manchester University}

\begin{Article}

\section{Introduction}
In this article I hope to give a `guided tour' around the files
that make up the basic \LaTeX\ distribution. Subsequent articles in
this mini-series will cover other packages by the \LaTeX\ development
team, and also some of the main contributed packages.

The primary source for \LaTeX\ is the `\textsc{ctan}\footnote
{\texttt{ftp.tex.ac.uk} in the UK}' network of archives, so
if I refer to path names of files this relates to the \textsc{ctan} file
structure. Note however that if you obtained \LaTeX\ as part of a
`pre-packaged' \TeX\ distribution, then these files may have been
moved (typically documentation files may be separated from \TeX\
source files). Hopefully this will not cause any confusion.

\section{The Components of \LaTeX}

The \LaTeX\ distribution at the \textsc{ctan} archives is organised into
the following directories.

\begin{filedesc}
\item[base] Contains the core \LaTeX\ files. You need at least these
files for a minimal \LaTeX\ installation.

\item[unpacked] Includes \emph{all} the files in \texttt{base}
together with the result of `unpacking' the source files. (More about
this later.) Thus when obtaining \LaTeX\ you should get either
\texttt{base} or \texttt{unpacked}, but not both. Getting the former
saves on time transferring the files, but getting the latter saves
time that would be taken unpacking the source files, so which is
preferable depends on the relative speed (and cost) of your machine
and your connection to the archives.

\item[packages] Consists of seven independent \LaTeX\ `extensions'
that are written and supported by the \LaTeX\ developers (or the
American Mathematical Society).

\texttt{amsfonts}, \texttt{amslatex}, \texttt{babel}, \texttt{graphics},
\texttt{mfnfss}, \texttt{psnfss} and \texttt{tools}

These packages will be described in more detail later in the series.

\item[fonts] The metafont sources and \TeX\
font metric files of a few fonts that \LaTeX\ requires that are not
part of the original plain \TeX\ distribution.

\item[doc] This directory is not part of the main \LaTeX\
distribution, it is generated by the \textsc{ctan} archives.
As a convenience
for those people that have not yet installed \LaTeX, some of the main
introductory documentation files which are available as \LaTeX\ files
in the base distribution are made available in this directory as dvi
and \PS\ files.

\item[contrib]  This directory contains an ever growing number of
contributed \LaTeX\ packages, and other extensions, that have been
contributed by \LaTeX\ users. They are not part of the `official'
\LaTeX\ distribution, but many of them form a vital part of any
`working' \LaTeX\ installation. The packages are divided into two
subdirectories `\texttt{supported}' and `\texttt{other}', however at
the current time one should ignore this distinction when looking for
packages to fetch from the archives. Contrary to
expectations some of the best supported packages are distributed (at
their author's request) from \path|contrib/other|.
\end{filedesc}

Unfortunately (for mainly historical reasons) people in search of
contributed \LaTeX\ packages also need to look in more distant
\textsc{ctan} directories.
Firstly, the \path|macros/latex209/contrib| area on
\textsc{ctan} contains packages that were written for the previous
version of \LaTeX\ that has been obsolete for 19 months now.
Any packages that are still distributed from this \LaTeX2.09 tree are
likely to be less than well supported, but you can still find some
useful files there.
Secondly, there are some packages that work with multiple formats, not
just \LaTeX, and these are to be found under \path|macros/generic|
or in their own top-level directory, such as \path|macros/musictex|.

\section{Documentation in the Base Distribution}
The documentation that comes with \LaTeX\ is of two forms: plain
(ASCII) text files with extension \texttt{.txt}, or \LaTeX\ documents
distributed as \LaTeX\ source with extension \texttt{.tex}.
Generally speaking the text files are mainly of interest to people
installing \LaTeX, who may need information before they have a working
system. Information of more general interest to \LaTeX\ users is
normally distributed as a \LaTeX\ document.

\subsection{The ASCII text files}
\subsubsection{Installation instructions}
\begin{filedesc}
\item[00readme] Provides a general introduction to the system,
and should be the first file to look at when installing \LaTeX\ for
the first time. 
\item[install] Provides `generic' installation instructions, but for
many \TeX\ versions  more specific 
specific instructions that have been contributed by the authors or
users of those systems, thus \File|emtex| gives instructions for the
popular em\TeX\ implementation, \File|web2ctex| gives specific
instructions on installing under \textsc{unix}, etc.

\item[tex2] If you have a \TeX\ that pre-dates version 3.0 (which was
released in 1989) by far the best thing to do is to update your \TeX,
but if that is really not possible this file details how \LaTeX\ may
be built under \TeX2.

\item[autoload] Describes the installation of an `autoloading' version
of \LaTeX. 
This produces a much smaller format by saving less common commands in
external files rather than in memory. These files are automatically
`autoloaded' as required. 
This version of \LaTeX\ is particularly recommended if you are using
a small installation (for instance a `small' em\TeX\ on a sub-386 PC). 

\end{filedesc}

\subsubsection{Other text files}

\begin{filedesc}
\item[legal] Contains the copyright notices and distribution
conditions for \LaTeX.

\item[bugs] Contains instructions on how to compile a bug report
            (see below).

\item[patches] Describes the \LaTeX\ patch mechanism that is used for
 distributing small updates between the `full' releases. This file
also contains a list of all the files that have changed since the last
full release. 
\item[changes] 
A Change Log of all the changes made to the \LaTeX\ files.
This is mainly intended for internal use by the \LaTeX\ developers,
but some people like to read it.
\end{filedesc}


\subsection{The \LaTeX\ `guides'}

These documents are distributed as \LaTeX\ source (i.e, \texttt{.tex}
files)  although as noted in the above introduction, the \textsc{ctan}
archives distribute most of them in ready-formatted versions in the
directory \path|latex/doc| so you can read these before installing
\LaTeX\ if you wish.
Unlike the ASCII text files described above, most of these documents 
are primarily intended for \emph{users} of the system rather than
system managers and software installers.

\begin{filedesc}
\item[usrguide] \emph{\LaTeXe\ for Authors}. 
This document describes all the main new features of
the 2e release of \LaTeX. It was written originally with the user of
the old \LaTeX\,2.09 in mind, but newcomers to \LaTeX\ who have never
used the old version should still gain something by reading this
document. It does not however cover the majority of \LaTeX\ commands
that were not changed, and so it is not a substitute for a full
\LaTeX\ manual.
\item[clsguide] \emph{\LaTeXe~for class and package writers}.
 A companion to to \texttt{usrguide}, gives details of
the \LaTeX\ commands for structuring class files and extension
packages.
\item[fntguide] \emph{\LaTeXe{} font selection}.
For font addicts only, but if you want to know the detailed
specification of the `New Font Selection Scheme' commands, here is the
place to look.
\item[cfgguide] \emph{Configuration options for \LaTeXe}.
Discusses what you can (and can not) do to configure a \LaTeX\
installation to the requirements of your local site.
\item[ltx3info] \emph{The \LaTeX3 Project}. A brief summary of the
aims of the \LaTeX3 project, the group of volunteers that has taken on
the maintenance and development of \LaTeX.
\item[modguide] \emph{Modifying \LaTeX}. This document discusses some
of the rationale behind the \LaTeX\ distribution conditions as
expressed in \texttt{legal.txt} and \texttt{cfgguide.tex}. Unless you
are making a distribution of a modified version of \LaTeX, or are
particularly interested in software copyright issues, you probably do
not want to read this.
\end{filedesc}

\subsection{\LaTeX~News}
As well as these larger documents there are a series of one-page
`newsletters'. A new one is produced with each full release of \LaTeX.
These detail any changes that have occurred in \LaTeX\
or the main extension packages over the six months since the previous
release. (\LaTeX\ releases  occur at regular intervals, in June and
December of each year.) Currently the four files
\texttt{ltnews01}--\texttt{ltnews04} are distributed corresponding to
the four releases of \LaTeX\ since June 1994.

\subsection{Example Documents}
There are two (very) small example documents, as described in the
\LaTeX\ book by Leslie Lamport.
\begin{filedesc}
\item[small2e] A very small (1 page) \LaTeX\ document.
\item[sample2e] A slightly larger document.
\end{filedesc}


\subsection{Documented sources}
The source for the \LaTeX\ format, and for all the packages and
classes in the core distribution is distributed as `\texttt{dtx}'
files. These are \LaTeX\ documents which may be processed in the usual
way to produce typeset documentation.
For example a command such as  \texttt{latex ltpictur.dtx}
would produce documented source of the picture mode commands.
The files with names of the form 
`\texttt{lt}\ldots\texttt{.dtx}' make up the source of
the \LaTeX\ format. If you want to produce a combined document
incorporating all these files, you may process
\File|source2e.tex|. This document will
produce a typeset version of the \LaTeX\ sources, together with
change log and index. It is well over 500 pages long, and so may take a
long time to produce. It may produce an index that is too large to be
handled by the `makeindex' program on smaller machines.


\subsection{Errata}
The principal documentation for \LaTeX\ is the two books \emph{\LaTeX:
A Document Preparation System}, and \emph{The \LaTeX\ Companion}.
Errata for these (and the German edition of \emph{The Companion}) are
available as \texttt{manual.err}, \texttt{compan.err} and
\texttt{begleit.err}.

\section{The \LaTeX\ Bug Report Database}
As described in the file \texttt{bugs.txt} mentioned above, the
\LaTeX3 project maintain a database of bug reports for \LaTeX.

If, after checking with colleagues, reading the manual, etc.,\  you
decide that some behaviour of \LaTeX\ is incorrect then you may
send a message to the \LaTeX\ bug database. Before doing this
you should check that your \LaTeX\ is not more than one year old (the
bug my have been fixed in a recent release). If you have access
to the World Wide Web, you may access the database and see if the
problem is already reported by using the search page accessible from:
\URL|http://www.tex.ac.uk/CTAN/latex/bugs.html|.

If you decide to send a report, two files are available to help compose
a message in the correct format:
\begin{filedesc}
\item[latexbug.tex] \LaTeX\ this file and you will be prompted for
information such as your name, and the name of a test file that shows
the problem. A mail message will be written to the file
\File|latexbug.msg| which should be sent to 
\Email|latex-bugs@uni-mainz.de|. 
(You should  \emph{always} use \File|latexbug.tex| to generate
messages to be sent to this bug address. It is an interface to
a database (The GNU GNATS problem tracking system) and can not handle
messages that are not in the special format written by
\File|latexbug.tex|. 
\item[latexbug.el] For users of the GNU Emacs text editor, a more
convenient interface is provided by this file. It runs
\File|latexbug.tex| automatically, and provides online help for
filling in the various fields, and finally automatically mails the
message to the correct address.
\end{filedesc}

\section{Docstrip files}
As mentioned above, \LaTeX\ is distributed as documented
sources. The files that are actually used by \TeX\ are extracted from
these files by running \File|docstrip.tex|. The \LaTeX\ distribution
contains many files with extension \texttt{.ins} that control how
\texttt{docstrip} extracts each file. Most of these are never used
individually, as they would just `unpack' one small part of the
distribution. The file \File|unpack.ins| is a `master' installation
script that calls the smaller install files in turn and so unpacks the
whole distribution. Normally running \TeX\ on this file is the first
step in installing \LaTeX. This step may be omitted however if the
\File|unpacked| directory is obtained from \textsc{ctan} rather than
\File|base|. \File|unpacked| is \emph{exactly} the result of obtaining
base and running \TeX\ on \File|unpack.ins|. If you have a slow
machine you may prefer this route as it saves unpacking time, but
conversely it requires downloading more files, so if you are
transferring the files via a slow connection such as a modem
then you may prefer to get the smaller `base' distribution.

There are three install files that are \emph{not} included into
\File|unpack.ins| so you may have need to run these if you need the
following features.
\begin{filedesc}
\item[autoload] Processing \File|autoload.ins| will generate
the source file for the `autoload' version of
\LaTeX, \File|latexa.ltx|, 
as described in \File|autoload.txt|. This should be processed
with ini\TeX\ to create a format file to be used in place of the
standard \File|latex.fmt|. As well as the modified format, various
packages are created containing the code that has been taken out of the
format. Normally these do not need to be invoked explicitly as they
are loaded on demand when they are needed. Currently the following
package files are produced.
\begin{filedesc}
\item[autopict] Source for \env{picture}  mode.
\item[autotabg] Source for \env{tabbing} environment.
\item[autoerr] The texts of most \LaTeX\ error commands.
\item[autofss1] Less used font selection commands.
\item[autoout1] Code related to \verb|\enlargethispage|.
\end{filedesc}
The autoload format is still quite experimental, and so the range of
such `autoloading' packages may change with future releases.
\item[cmextra] Processing \File|cmextra.ins| installs the 
`\texttt{fd}' files
for the `concrete' variants of the Computer Modern fonts, and also the
AMS Cyrillic fonts.
\item[olddc] If using the Computer Modern fonts in the 8-bit `T1'
encoding, \LaTeX\ defaults to using the `dc fonts'. During 1995 these
fonts were updated and the names of the fonts \emph{changed}. Thus the
10\,pt roman font corresponding to \File|cmr10| is now \File|dcr1000|
rather than \File|dcr10|. The install file \File|unpack.ins| includes
\File|newdc.ins| so by default \LaTeX\ will use the new 1995 names (dc
fonts release 1.2 or later) when using T1 font encoding. If you still
have the old dc fonts, then you must process \File|olddc.ins| to
produce suitable \texttt{fd} files referring to the old names.
\end{filedesc}

\section{The Standard \LaTeX\ Classes}

The general appearance of a \LaTeX\ document, and the specification
of the commands available is specified in a \emph{document
class}. This may be further modified by loading \emph{packages}, as
described in \texttt{usrguide}. In this section I give a brief
overview of the available classes in the base distribution. They all
have extension \texttt{.cls} (after being unpacked from the
\texttt{.dtx} source file during the installation process).

\begin{filedesc}
\item[article] `\class{Article} Class'. In some sense the canonical
reference class against which all others are judged.
This class (which is generated from the same \File|classes.dtx| source
as \class{report} and \class{book} described below) is a mixed blessing.
On one hand it provides quite a rich collection of commands for marking
up documents that means that it serves well as as the basic `generic'
class to be used when no more suitable specific class is available. On
the other hand the visual appearance of documents produced with this
class is very distinctive. Many people who say they
``don't like \LaTeX''
and so use some other format such as plain, in fact are misled into
believing that \LaTeX\ \emph{is} this class. In fact by loading
\class{article} and then making small adjustments one can produce
very different visual designs. The class file for \BV~ is an example of
such a non-standard class based on \class{article}.

However for many purposes, portability is more important than
original typographical design, and in these cases the \class{article}
class has the big advantage of being installed at all \LaTeX\ sites.

\item[report] `\class{Report} Class'. Very similar to \class{article}
 (and produced from the same source).
The main differences being that this class has a
higher level of sectioning command (\verb|\chapter|) than is available
in \class{article}, and the front matter is typeset differently.

\item[book] The \class{book} class is again very similar to
\class{report}
with the addition of a few extra features for controlling the front
matter and back matter.
It is unlikely that you would want to use this class `as
is' as for a book, you would almost certainly want to spend some
effort (and perhaps money!) on an original design. However it can be
used as a basis or example of the implementation of a \LaTeX\ class
for book production.

\item[letter] This provides commands for producing one or more
letters. Many sites use this as a basis for producing site-specific
letter class files, for instance with a modified heading that inserts
a departmental logo and address.\footnote{One should be able to
find details of such local variants in the famous `local guide'.}


\item[proc] Proceedings class. This is a variant of \class{article}
class (and inputs the \File|article.cls| file when used).
It defaults to two column mode and makes one or two other small
adjustments. It may be used as a model for how make a class that
builds on another.

\item[slides] The \class{slides} class.
This class essentially provides the functionality that was formally
built into \SLiTeX. It provides a
mechanism for producing pages suitable for projecting on an overhead
projector. It is described in the \LaTeX\ book, and some people like
it, however if you are making a lot of such presentations you may
prefer to look at the contributed classes \class{seminar}
(T.~v.~Zandt) or \class{foiltex} (J. Hafner). these provide alternatives
to the standard class that many people find more useful.

\end{filedesc}

As well as these `Standard Classes' the base distribution contains a
few other special purpose classes.

\begin{filedesc}
\item[minimal] This is the minimal \LaTeX\ class.
It just sets up a text area, and a font in a single size.
None of the normal sectioning or font size commands are available. 
This class is not intended to be used in documents, but it is often
useful when testing macros as it loads very quickly.
\item[ltxguide] A special purpose class for the `\LaTeX\ guides'
mentioned earlier. 
\item[ltnews] The class file used for the `\LaTeX~News' news sheets.
\item[ltxdoc] This class is used in all the \texttt{dtx} documentation
files. It is based on the \class{article} class and the \package{doc}
package, but with additional commands for documenting the \LaTeX\
sources. It was not conceived as a class for general use, but some
people find it convenient to use it when documenting their own package
files.
\end{filedesc}


\section{Standard Packages}

\subsection{Encoding Packages}
One of the main features of the 2e release of \LaTeX\ is that it
attempts to remove all `hard wired' assumptions about the encodings
being used, both for input and also in the fonts used for typesetting.

It maintains a strict distinction between the \emph{Input Encoding}
and the \emph{Output Encoding}. The input encoding relates to the text
that you type, this may be a standard encoding such as ASCII (The
traditional 7-bit encoding) or ISO-latin-1, or
a platform specific encoding such as `Windows ANSI' as used on
MicroSoft Windows 3.x machines.
The output encoding for text fonts is usually either OT1 (The encoding
devised by Knuth and implemented in the original Computer Modern \TeX\
fonts.) or T1 the new \TeX\ encoding also known as `Cork' after the
meeting where it was agreed.

\LaTeX\ maintains this separation by \emph{always} translating input
to an \emph{Internal Encoding}. This is essentially traditional \TeX\
7-bit input. This internal encoding is then translated to the encoding
used in the font without reference to the original input mechanism
used. Thus if you specify an input encoding that includes the
character \textbf{\'{e}} you may type that directly at the keyboard,
and see it as a single character, however internally \LaTeX\ will
treat this as \verb|\'{e}|. If you are using 7-bit OT1 encoded fonts
this command will use the \verb|\accent| primitive to add an accute to
the \textbf{e}, however if you are using T1 fonts, the existing
\textbf{\'{e}} will be accessed directly. Note however that the
position of \textbf{\'{e}} in the output encoding (T1) is typically
\emph{different} from the position of the character in the input
encoding used.
\begin{filedesc}
\item[inputenc] 
Specifies that an 8-bit input encoding is being used. 
A package option should always be used which sets up
the default encoding. The currently available options
include \package{latin1}, \package{latin2},
\package{ansinew}, \package{cp437}, \package{cp437de},
\package{applemac}. (The two IBM codepage 437 variants differ just in
one slot, the former uses $\beta$, the latter uses \ss.)

So typical usage (to specify ISO Latin-1 input conventions) would be:\\
\verb|\usepackage[latin1]{inputenc}|

\item[fontenc]
Specifies the default output encoding for text fonts. Currently
the available options are \package{OT1} and \package{T1}.
So to specify that fonts in the the T1 (Cork) encoding be used in the
document one would declare:\\
\verb|\usepackage[T1]{fontenc}|

\end{filedesc}

\subsection{Remaining Packages in the Base Distribution}
\begin{filedesc}
\item[alltt] Defines the \env{alltt} environment, similar to
\env{verbatim} except  that \verb|\|, \verb|{| and \verb|}| retain
their usual \TeX\ meanings.
\item[doc]  The package defining the commands used for documenting all
the \LaTeX\ code in the distribution.
\item[shortvrb] This package (really a small part of the \package{doc}
package) defines the \verb|\MakeShortVerb| command that allows
shorthands like \verb"|\foo|"  instead of \verb"\verb|\foo|" This is
very convenient if you are documenting \TeX\ or some other situation
where you need to make a lot of use of short sections of verbatim text.
\item[exscale]  For mainly historical reasons \LaTeX\ always uses the
math extension font (used for brackets and sum and integral signs
etc.) at the same size, whatever the current font size. This package
modifies this behaviour so that magnified fonts are used at larger
sizes. At the same time it makes the plain \TeX\ commands \verb|\big|,
\verb|\bigg| etc., work as expected in conjunction with \LaTeX\ size
commands. 
\item[flafter] \LaTeX\ floats such as the \env{figure} and
\env{table} environment can float \emph{up} to the top of the
current page. This means that it is possible that the figure appears
before its first reference. Some publisher's styles do not allow
this. \package{flafter} redefines the float placement algorithm so that
a float never appears before its position in the source file, so by
using this package, and placing the \env{figure} environment after
the first reference to the figure, one can ensure that figure will
appear after the reference.
\item[graphpap] The \verb|\graphpaper| command produces a grid for use
in the \env{picture} environment.
\item[ifthen] Provides an `if \ldots then \ldots else\ldots' programming
construct for use in \LaTeX\ packages. Many of the examples in `The
\LaTeX\ Companion' assume this package has been loaded.
\item[makeindx]   Implements support for generating an index.
\item[pict2e]     This package produces an error message to say that
it has not been written. Even if it were written one would be advised
to instead use the \package{PSTricks} package, as described in
Sebastian Rahtz' article elsewhere in this issue.
\item[showidx]    This causes the argument of each \verb|\index|
command to be printed on the page where it occurs. See also
\File|idx.tex| described below.
\item[syntonly] Used to process a document without
   typesetting it. On some systems this speeds things up considerably,
and so may (possibly) be useful while debugging documents.
\item[tracefnt] This allows you to control how much information about
   \LaTeX's font loading is displayed.
\item[latexsym] Loads the special \LaTeX\ symbol font and then
defines commands such as \verb|\Box| that use this font. These
commands were defined by default in \LaTeX2.09.
\item[newlfont]   Defines `old' font commands to act in the `new'
way. For example it makes \verb|\rm| essentially equivalent to
\verb|\rmfamily|. This package is not now recommended but is
distributed so old documents written using the \LaTeX2.09 version of
this package still work. 
\item[oldlfont] A companion to \package{newlfont}. This package is
only to be used for old documents that used the \LaTeX2.09 package of
the same name.
\end{filedesc}

\section{Font Definition Files}
Unpacking the \LaTeX\ distribution creates dozens of `font definition
files' with extension `\texttt{.fd}' from their documented sources (with
extension \texttt{.fdd}). These map the internal \LaTeX\ model of fonts
on to the external file names as used on your system. Normally you
never need to load these explicitly into a \LaTeX\ document and they
will not be considered in detail here except to say that if you
obtain some new fonts from the \TeX\ archives, make sure to also get
the related \texttt{fd} files, and install them where \LaTeX\ can
find them.

\section{Makeindex Styles}
The distribution includes three styles (with extension \texttt{.ist})
for the \emph{makeindex} index generator. They modify the makeindex
defaults so as to work with the special requirements of the
\package{doc} package.

\begin{filedesc}
\item[gind] Produces indices of command definition and use.
\item[gglo] Produces `change log' entries (using the \LaTeX\
\verb|\glossary| command rather than \verb|\index|).
\item[source2e] This style is only produced if the \LaTeX\ document
\File|source2e.tex| is processed. It is almost identical to
\File|gind.ist| but defines `I' to be in the series
`\mbox{I--J--K}' rather than `\mbox{I--II--III}'. This is needed for
the numbering conventions used in that document.
\end{filedesc}
\section{Miscellaneous Utilities and Files}
\begin{filedesc}
\item[idx.tex]          Print out index entries in your document.
\item[lablst.tex]       Generate list of labels used in a
document. You may prefer instead to have the labels show up in the
margins of your drafts, in which case use the \package{showkeys}
package from the `tools' collection to be described later in this
`tour'.
\item[ltxcheck.tex] This `document' should always be processed after
\LaTeX\ has been installed. It produces no output but checks various
components of the system are configured correctly for your machine
type.
\item[nfssfont.tex]      Test file for testing a font. A more
extensive font test is available if you use the \package{fontsmpl}
package from the `tools' collection.
\item[testpage.tex]      Test file for checking the accuracy of a
printer. This is particularly useful to see if you need to specify any
offsets to your printer driver to ensure that the printed text is
correctly positioned on the paper.
\item[Makefile.unx]     A very simplistic template `Makefile' for
installing the \LaTeX\ base distribution under \textsc{unix}.
Many \textsc{unix} \TeX\
distributions come with far more suitable installation procedures. For
example the excellent `te\TeX' distribution allows you to install \TeX,
\LaTeX, metafont, dvips, xdvi, and a host of other utilities and fonts
just by typing \texttt{sh install.sh}.
\item[latex209.def] This file is loaded whenever a document begining
with \verb|\documentstyle| is seen. It forces \LaTeX\ into `2.09
compatibility mode' which is exceedingly slow, but a fairly accurate
emulation of the old version of \LaTeX. This enables old documents to
be processed under the current system.
\end{filedesc}
\end{Article}
