\input texinfo
@c $Id: latex2e.texi 578 2017-08-06 00:04:43Z jimhefferon $
@comment %**start of header (This is for running Texinfo on a region.)
@setfilename latex2e.info
@set UPDATED August 2017
@include common.texi
@settitle @LaTeX{}2e unofficial reference manual (@value{UPDATED})
@comment %**end of header (This is for running Texinfo on a region.)

@c latex 2.09 commands should all be present now,
@c xx but latex2e stuff is missing.
@c xx random list of a few of the missing items is at the end of this file
@c
@c xx misc commands from clsguide.pdf: \ignorespacesafterend,
@c   \normalsfcodes
@c xx color (include info from clsguide.pdf)
@c xx ending a run with errors
@c xx ctan, distributions, components of TeX
@c xx classes and packages -- required, additional, useful; oberdiek; fonts
@c
@c xx merge http://ctan.org/pkg/latex-info (CTAN package latex-info)
@c xx merge http://ctan.org/pkg/latex2e-reference
@c xx merge permuted-index
@c xx merge latex-manual from savannah
@c xx merge display style math
@c xx vertical mode, horizontal mode
@c
@c xx The typeset source2e has an index with all kernel
@c xx commands, though some are internal and shouldn't be included.
@c xx classes.dtx et al. define additional commands.
@c xx See also http://ctan.org/pkg/macros2e.

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

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

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

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

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

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

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

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

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

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

@shortcontents
@contents

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

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

@clear HAS-MATH 
@iftex
@set HAS-MATH
@end iftex

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

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

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


@node About this document
@chapter About this document

@findex @url{@value{LTXREFMAN_HOME_PAGE}} @r{home page}
This is an unofficial reference manual for the @LaTeX{}2e document
preparation system, which is a macro package for the @TeX{}
typesetting program (@pxref{Overview}).  This document's home page is
@url{@value{LTXREFMAN_HOME_PAGE}}.  That page has links to the
current output in various formats, sources, mailing list archives and
subscriptions, and other infrastructure.

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

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

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

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

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

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

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

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

@end table


@node Overview
@chapter Overview of @LaTeX{}

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

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

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

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

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

@menu
* Starting and ending::  The standard beginning and end of a document.
* Output files::         Files produced.
* @TeX{} engines::          Programs that can compile @TeX{} and  @LaTeX{}.
* @LaTeX{} command syntax:: General syntax of @LaTeX{} commands.
@end menu


@node Starting and ending
@section Starting and ending

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

@LaTeX{} files have a simple global structure, with a standard beginning
and ending.  Here is a ``hello, world'' example:

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

@cindex document class, defined
@noindent
Here, the @samp{article} is the so-called @dfn{document class},
implemented in a file @file{article.cls}.  Any document class can be
used.  A few document classes are defined by @LaTeX{} itself, and vast
array of others are widely available.  @xref{Document classes}.

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

The @code{\begin@{document@} ... \end@{document@}} is a so-called
@cindex environment
@dfn{environment}; the @samp{document} environment (and no others) is
required in all @LaTeX{} documents (@pxref{document}).  @LaTeX{}
provides many environments itself, and many more are defined separately.
@xref{Environments}.

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


@node Output files
@section Output files

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

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

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

@end table

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

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

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

@end table

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


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

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

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

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

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

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

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

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

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

@end table

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


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

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

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

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

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

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

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

@menu
* Environment::          Area of the source with distinct behavior.
* Declaration::          Change the value or meaning of a command.
* \makeatletter and \makeatother::    Change the status of the at-sign character.
@end menu


@node Environment
@subsection Environments

Synopsis:

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

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

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

See@tie{}@ref{Environments} for a list of environments. 

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

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

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


@node Declaration
@subsection Command declarations

A command that changes the value, or changes the meaning, of some other
command or parameter.  For instance, the @code{\mainmatter} command
changes the setting of page numbers from roman numerals to arabic.


@node \makeatletter and \makeatother
@subsection @code{\makeatletter} and @code{\makeatother}

Synopsis:

@example
\makeatletter
  ... definition of commands with @@ in their name ..
\makeatother
@end example

Used to redefine internal @LaTeX{} commands.  @code{\makeatletter} makes
the at-sign character@tie{}@code{@@} have the category code of a letter,
11.  @code{\makeatother} sets the category code of@tie{}@code{@@} to 12,
its original value.

As each character is read by @TeX{} for @LaTeX{}, it is assigned a
character category code, or 
@cindex catcode
@cindex character category code
@cindex category code, character
@dfn{catcode} for short. For instance, the backslash@tie{}@code{\} is
assigned the catcode 0, for characters that start a command.  These two
commands alter the catcode assigned to @code{@@}.

The alteration is needed because many of @LaTeX{}'s commands use
@code{@@} in their name, to prevent users from accidentally defining a
command that replaces one of @LaTeX{}'s own.  Command names consist of a
category@tie{}0 character, ordinarily backslash, followed by letters,
category@tie{}11 characters (except that a command name can also consist
of a category@tie{}0 character followed by a single non-letter symbol).
So under the default category codes, user-defined commands cannot
contain an @code{@@}.  But @code{\makeatletter} and @code{\makeatother}
allow users to define or redefine commands named with @code{@@}.

Use these two commands inside a @file{.tex} file, in the preamble, when
defining or redefining a command with @code{@@} in its name.  Don't use
them inside @file{.sty} or @file{.cls} files since the
@code{\usepackage} and @code{\documentclass} commands set the at sign to
have the character code of a letter.

@PkgIndex{macros2e}
For a comprehensive list of macros with an at-sign
in their names see @url{http://ctan.org/pkg/macros2e}. These macros are
mainly intended to package or class authors.

The example below is typical.  In the user's class file is a command
@code{\thesis@@universityname}.  The user wants to change the
definition.  These three lines should go in the preamble, before the
@code{\begin@{document@}}.

@example
\makeatletter
\renewcommand@{\thesis@@universityname@}@{Saint Michael's College@}
\makeatother
@end example

@menu
* \@@ifstar:: Define your own commands with *-variants.
@end menu


@node \@@ifstar
@subsubsection @code{\@@ifstar}

@findex \@@ifstar
@cindex commands, star-variants
@cindex star-variants, commands

Synopsis:

@example
\newcommand@{\mycmd@}@{\@@ifstar@{\mycmd@@star@}@{\mycmd@@nostar@}@}
\newcommand@{\mycmd@@nostar@}[@var{non-starred command number of args}]@{@var{body of non-starred command}@} 
\newcommand@{\mycmd@@star@}[@var{starred command number of args}]@{@var{body of starred command}@}
@end example

Many standard @LaTeX{} environments or commands have a variant with the
same name but ending with a star character@tie{}@code{*}, an asterisk.
Examples are the @code{table} and @code{table*} environments and the
@code{\section} and @code{\section*} commands.

When defining environments, following this pattern is straightforward
because @code{\newenvironment} and @code{\renewenvironment} allow the
environment name to contain a star.  For commands the situation is more
complex.  As in the synopsis above, there will be a user-called command,
given above as @code{\mycmd}, which peeks ahead to see if it is followed
by a star.  For instance, @LaTeX{} does not really have a
@code{\section*} command; instead, the @code{\section} command peeks
ahead.  This command does not accept arguments but instead expands to
one of two commands that do accept arguments.  In the synopsis these two
are @code{\mycmd@@nostar} and @code{\mycmd@@star}.  They could take the
same number of arguments or a different number, or no arguments at all.
As always, in a @LaTeX{} document a command using at-sign@tie{}@code{@@}
must be enclosed inside a @code{\makeatletter ... \makeatother} block
(@pxref{\makeatletter and \makeatother}).

This example of @code{\@@ifstar} defines the command @code{\ciel} and a
variant @code{\ciel*}.  Both have one required argument.  A call to
@code{\ciel@{night@}} will return "starry night sky" while
@code{\ciel*@{blue@}} will return "starry not blue sky".

@example
\newcommand*@{\ciel@@unstarred@}[1]@{starry #1 sky@}
\newcommand*@{\ciel@@starred@}[1]@{starry not #1 sky@}
\newcommand*@{\ciel@}@{\@@ifstar@{\ciel@@starred@}@{\ciel@@unstarred@}@}
@end example

In the next example, the starred variant takes a different number of
arguments than does the unstarred one.  With this definition, Agent
007's @code{``My name is \agentsecret*@{Bond@},
\agentsecret@{James@}@{Bond@}.''} is equivalent to @code{``My name is
\textsc@{Bond@}, \textit@{James@} textsc@{Bond@}.''}

@example
\newcommand*@{\agentsecret@@unstarred@}[2]@{\textit@{#1@} \textsc@{#2@}@}
\newcommand*@{\agentsecret@@starred@}[1]@{\textsc@{#1@}@}
\newcommand*@{\agentsecret@}@{\@@ifstar@{\agentsecret@@starred@}@{\agentsecret@@unstarred@}@}
@end example

There are two sometimes more convenient ways to accomplish the work of
@code{\@@ifstar}.  The @file{suffix} package allows the construct
@code{\newcommand\mycommand@{@var{unstarred version}@}} followed by
@code{\WithSuffix\newcommand\mycommand*@{@var{starred version}@}}.  And
@LaTeX{}3 has the @file{xparse} package that allows this code.

@example
\NewDocumentCommand\foo@{s@}@{\IfBooleanTF#1
  @{@var{starred version}@}%
  @{@var{unstarred version}@}% 
  @}
@end example


@node Document classes
@chapter Document classes

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

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

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

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

@table @code
@item article
For a journal article, a presentation, and miscellaneous general use.

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

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

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

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

@end table

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

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


@node Document class options
@section Document class options

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

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

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

Here is the list of the standard class options.

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

@example
10pt  11pt  12pt
@end example

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


@node Additional packages
@section Additional packages

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

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

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

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


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

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

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

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

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


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


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

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

A class file or package file typically has four parts.  
@enumerate
In the @dfn{identification part}, the file says that it is a @LaTeX{}
package or class and describes itself, using the @code{\NeedsTeXFormat}
and @code{\ProvidesClass} or @code{\ProvidesPackage} commands.
@item
The @dfn{preliminary declarations part} declares some commands and
can also load other files. Usually these commands will be those needed
for the code used in the next part.  For example, an @code{smcmemo}
class might be called with an option to read in a file with a list of
people for the to-head, as @code{\documentclass[mathto]@{smcmemo@}}, and
therefore needs to define a command
@code{\newcommand@{\setto@}[1]@{\def\@@tolist@{#1@}@}} used in that
file.
@item
In the @dfn{handle options part} the class or package declares
and processes its options.  Class options allow a user to start their
document as @code{\documentclass[@var{option list}]@{@var{class
name}@}}, to modify the behavior of the class.  An example is when you
declare @code{\documentclass[11pt]@{article@}} to set the default
document font size.  
@item
Finally, in the @dfn{more declarations part} the class or package usually does
most of its work: declaring new variables, commands and fonts, and
loading other files.
@end enumerate


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


@item \IfFileExists@{@var{file name}@}@{@var{true code}@}@{@var{false code}@}
@item \InputIfFileExists@{@var{file name}@}@{@var{true code}@}@{@var{false code}@}
@findex \IfFileExists
@findex \InputIfFileExists
Execute @var{true code} if @LaTeX{} can find the file @file{@var{file
name}} and @var{false code} otherwise.  In the second case it inputs the
file immediately after executing @var{true code}.  Thus
@code{\IfFileExists@{img.pdf@}@{\includegraphics@{img.pdf@}@}@{\typeout@{WARNING:
img.pdf not found@}@}} will include the graphic @file{img.pdf} if it is
found but otherwise just give a warning.

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

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

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

If you request a @var{release date} and the date of
the package installed on your system is earlier, then you get a warning
on the screen and in the log like @code{You have requested, on input
line 4, version `2038/01/19' of document class article, but only version
`2014/09/29 v1.4h Standard LaTeX document class' is available.}

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

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

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

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

To specify a version of the format that you know to have certain
features, include the optional @var{format date} on which those features
were implemented.  If present it must be in the form @code{YYYY/MM/DD}.
If the format version installed on your system is earlier than
@var{format date} then you get a warning like @samp{You have requested
release `2038/01/20' of LaTeX, but only release `2016/02/01' is
available.}

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

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

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

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

If your own code is bringing in a package twice then you can collapse
that to once, for example replacing the two
@code{\RequirePackage[landscape]@{geometry@}\RequirePackage[margins=1in]@{geometry@}}
with the single
@code{\RequirePackage[landscape,margins=1in]@{geometry@}}.  But if you
are loading a package that in turn loads another package then you need
to queue up the options you desire for this other package.  For
instance, suppose the package @code{foo} loads the package
@code{geometry}.  Instead of
@code{\RequirePackage@{foo@}\RequirePackage[draft]@{graphics@}} you must
write @code{\PassOptionsToPackage@{draft@}@{graphics@}
\RequirePackage@{foo@}}.  (If @code{foo.sty} loads an option in conflict
with what you want then you may have to look into altering its source.)

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

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

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

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

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

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


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

When a user writes @code{\documentclass@{smcmemo@}} then @LaTeX{} loads
the file @file{smcmemo.cls}.  Similarly, a user writing
@code{\usepackage@{test@}} prompts @LaTeX{} to load the file
@code{test.sty}.  If the name of the file does not match the declared
class or package name then you get a warning.  Thus, if you invoke
@code{\documentclass@{smcmemo@}}, and the file @file{smcmemo.cls} has
the statement @code{\ProvidesClass@{xxx@}} then you get a warning like
@code{You have requested document class `smcmemo', but the document
class provides 'xxx'.}  This warning does not prevent @LaTeX{} from
processing the rest of the class file normally.

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

The date in the optional argument allows class and package users to ask
to be warned if the version of the class or package installed on their
system is earlier than @var{release date}, by using the optional arguments
such as @code{\documentclass@{smcmemo@}[2018/10/12]} or
@code{\usepackage@{foo@}[[2017/07/07]]}.  (Note that package users only
rarely include a date, and class users almost never do.)

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

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

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

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

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


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

@cindex typefaces
@cindex fonts

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

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


@node Font styles
@section Font styles

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

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

This first group of commands is typically used with an argument, as in
@code{\textit@{@var{text}@}}.  In the table below, the corresponding
command in parenthesis is the ``declaration form'', which takes no
arguments, as in @code{@{\itshape @var{text}@}}.  The scope of the
declaration form lasts until the next type style command or the end of
the current group.

These commands, in both the argument form and the declaration form,
are cumulative; e.g., you can say either @code{\sffamily\bfseries} or
@code{\bfseries\sffamily} to get bold sans serif.

You can alternatively use an environment form of the declarations; for
instance, @code{\begin@{ttfamily@}...\end@{ttfamily@}}.

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

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

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

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

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

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

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

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

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

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

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

@end table

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

@LaTeX{} also provides the following commands, which unconditionally
switch to the given style, that is, are @emph{not} cumulative.  Also,
they are used differently than the above commands:
@code{@{\@var{cmd}...@}} instead of @code{\@var{cmd}@{...@}}.  These
are two unrelated constructs.

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

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

@item \it
@cindex italic font
Italics.

@item \rm
@cindex roman font
Roman.

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

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

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

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

@end ftable

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

(Some people consider the unconditional font-switching commands, such
as @code{\tt}, obsolete and that only the cumulative commands
(@code{\texttt}) should be used.  Others think that both sets of
commands have their place and sometimes an unconditional font switch
is precisely what you want; for one example,
@pxref{description,,@code{description}}.)

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

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

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

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

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

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

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

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

@end table

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

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


@node Font sizes
@section Font sizes

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

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

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

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

The commands as listed here are ``declaration forms''. The scope of
the declaration form lasts until the next type style command or the
end of the current group.  You can also use the environment form of
these commands; for instance, @code{\begin@{tiny@}...\end@{tiny@}}.


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

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

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

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

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

@c Sorry about the ugly @t{@ }.  The idea is to make the lists line up
@c in Info.  Since the items are so short, it seems nice to have them
@c on the same line instead of using @table.

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

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

@itemize @w{}
@item @code{m}@t{@ } Medium (normal)
@item @code{b}@t{@ } Bold
@item @code{c}@t{@ } Condensed
@item @code{bc} Bold condensed
@item @code{bx} Bold extended
@end itemize

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

@itemize @w{}
@item @code{ul} Ultra light
@item @code{el} Extra light
@item @code{l}@t{@ } Light
@item @code{sl} Semi light
@item @code{m}@t{@ } Medium (normal)
@item @code{sb} Semi bold
@item @code{b}@t{@ } Bold
@item @code{eb} Extra bold
@item @code{ub} Ultra bold
@end itemize
 
@cindex widths, of fonts
The possible values for width, individually, are (the percentages
are just guides and are not followed precisely by all fonts):

@itemize @w{}
@item @code{uc} Ultra condensed, 50%
@item @code{ec} Extra condensed, 62.5%
@item @code{c}@t{@ } Condensed, 75%
@item @code{sc} Semi condensed, 87.5%
@item @code{m}@t{@ } Medium, 100%
@item @code{sx} Semi expanded, 112.5%
@item @code{x}@t{@ } Expanded, 125%
@item @code{ex} Extra expanded, 150%
@item @code{ux} Ultra expanded, 200%
@end itemize

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

@itemize @w{}
@item @code{n}@t{@ } Upright (normal)
@item @code{it} Italic
@item @code{sl} Slanted (oblique)
@item @code{sc} Small caps
@item @code{ui} Upright italics
@item @code{ol} Outline
@end itemize

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

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

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

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

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

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

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

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

@end table


@node Layout
@chapter Layout

@cindex layout commands

Commands for controlling the general page layout.

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


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

@findex \onecolumn
@cindex one-column output

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

This command is fragile (@pxref{\protect}).


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

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

Synopses:

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

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

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

This command is fragile (@pxref{\protect}).

These parameters control typesetting in two-column output:

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

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

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

@end ftable

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

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

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

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

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

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

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

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

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

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

@end ftable

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

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

Two column text here.
@end example


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

@findex \flushbottom

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

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

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


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

@findex \raggedbottom
@cindex stretch, omitting vertical

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

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


@node Page layout parameters
@section Page layout parameters

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

@end ftable


@node Floats
@section Floats

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

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

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

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

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

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

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

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

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

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

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

@end table

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


@node Sectioning
@chapter Sectioning

@cindex sectioning commands

Sectioning commands provide the means to structure your text into units:

@ftable @code
@item \part
@item \chapter
(@code{report} and @code{book} class only)
@item \section
@item \subsection
@item \subsubsection
@item \paragraph
@item \subparagraph
@end ftable

All sectioning commands take the same general form, e.g.,

@example
\chapter[@var{toctitle}]@{@var{title}@}
@end example

In addition to providing the heading @var{title} in the main text, the
section title can appear in two other places:

@enumerate
@item
The table of contents.
@item
The running head at the top of the page.
@end enumerate

You may not want the same text in these places as in the main text.
To handle this, the sectioning commands have an optional argument
@var{toctitle} that, when given, specifies the text for these other
places.

@cindex @code{*}-form of sectioning commands
Also, all sectioning commands have @code{*}-forms that print
@var{title} as usual, but do not include a number and do not make an
entry in the table of contents.  For instance:

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

@findex \appendix
@cindex appendix, creating
The @code{\appendix} command changes the way following sectional units
are numbered.  The @code{\appendix} command itself generates no text
and does not affect the numbering of parts.  The normal use of this
command is something like

@example
\chapter@{A Chapter@}
@dots{}
\appendix
\chapter@{The First Appendix@}
@end example

@findex secnumdepth @r{counter}
@cindex section numbers, printing
@anchor{Sectioning/secnumdepth}
The @code{secnumdepth} counter controls printing of section numbers.
The setting

@example
\setcounter@{secnumdepth@}@{@var{level}@}
@end example

@noindent
suppresses heading numbers at any depth @math{> @var{level}}, where
@code{chapter} is level zero.  (@xref{\setcounter}.)

@menu
* \@@startsection:: Redefine layout of start of sections, subsections, etc.
@end menu


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

@findex \@@startsection
@cindex section, redefining

Synopsis:

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

Redefine the behavior of commands that start sectioning divisions such
as @code{\section} or @code{\subsection}.

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

Technically, this command has the form:
@example
\@@startsection@{@var{name}@}@{@var{level}@}@{@var{indent}@}@{@var{beforeskip}@}@{@var{afterskip}@}@{@var{style}@}
    *[@var{toctitle}]@{@var{title}@}
@end example
@noindent so that issuing:
@example
\renewcommand@{\section@}@{\@@startsection@{@var{name}@}@{@var{level}@}@{@var{indent}@}%
     @{@var{beforeskip}@}@{@var{afterskip}@}@{@var{style}@}@}
@end example
@noindent redefine @code{\section} while keeping its standard calling form
@code{\section*[@var{toctitle}]@{@var{title}@}}.  @xref{Sectioning} and
the examples below.

@table @var

@item name
@anchor{\@@startsection/name} Name of the counter (which must be defined
separately) used to number for the sectioning header.  Most commonly
either @code{section}, @code{subsection}, or @code{paragraph}.  Although
in those three cases the name of the counter is also the name of the
sectioning command itself, using the same name is not required.

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

@item level
@anchor{\@@startsection/level} An integer giving the depth of the
sectioning command: 0 for @code{chapter} (only applies to the standard
@code{book} and @code{report} classes), 1 for @code{section}, 2 for
@code{subsection}, 3 for @code{subsubsection}, 4 for @code{paragraph},
and 5 for @code{subparagraph}.  In the @code{book} and @code{report}
classes @code{part} has level -1, while in the @code{article} class
@code{part} has level 0.

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

If @var{level} is less than or equal to the value of @var{tocdepth} then
the table of contents will have an entrie for this sectioning unit.
For instance, in an @code{article}, if @var{tocdepth} is 1 then the table of
contents will list sections but not subsections.
@c xx add, and cross reference to, tocdepth

@item indent
@anchor{\@@startsection/indent} A length giving the indentation of all
of the title lines with respect to the left margin.  To have the
title flush with the margin use @code{0pt}.  A negative indentation
such as @code{-1em} will move the title into the left margin.

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

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

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

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

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

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

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

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

This will put section titles in large boldface type, centered.

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

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

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

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

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


@node Cross references
@chapter Cross references

@cindex cross references

One reason for numbering things such as figures and equations is to
refer the reader to them, as in ``See Figure~3 for more details.''

@cindex label
Including the figure number in the source is poor practice since if that
number changes as the document evolves then you must remember to update
this reference by hand.  Instead, @LaTeX{} has you write a @dfn{label}
like @code{\label@{eq:GreensThm@}} and refer to it with @code{See
equation~\ref@{eq:GreensThm@}}.

@LaTeX{} writes the information from the labels to a file with the same
name as the file containing the @code{\label@{...@}} but with an
@file{.aux} extension.  (The information has the format
@code{\newlabel@{@var{label}@}@{@{@var{currentlabel}@}@{@var{pagenumber}@}@}}
where @var{currentlabel} is the current value of the macro
@code{\@@currentlabel} that is usually updated whenever you call
@code{\refstepcounter@{@var{counter}@}}.)

@cindex forward reference
@cindex reference, forward
The most common side effect of the prior paragraph happens when your
document has a @dfn{forward reference}, a @code{\ref@{@var{key}@}} that
appears earlier than the associated @code{\label@{@var{key}@}}; see the
example in the @code{\pageref@{...@}} description.  @LaTeX{} gets the
information for references from the @file{.aux} file.  If this is the
first time you are compiling the document then you will get a message
@code{LaTeX Warning: Label(s) may have changed. Rerun to get
cross references right.} and in the output the reference will appear as
two question marks@tie{}@samp{??}, in boldface.  Or, if you change some
things so the references change then you get the same warning and the
output contains the old reference information.  The solution in either
case is just to compile the document a second time.

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


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

@findex \label

Synopsis:

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

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

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

A common convention is to use labels consisting of a prefix and a suffix
separated by a colon or period.  This helps to avoid accidentally
creating two labels with the same name, and makes your source more
readable.  Some commonly-used prefixes:

@table @code
@item ch
for chapters
@item sec
for lower-level sectioning commands
@item fig
for figures
@item tab
for tables
@item eq
for equations
@end table

Thus, @code{\label@{fig:Euler@}} is a label for a figure with a portrait
of the great man.

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

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


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

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

Synopsis:

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

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

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

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


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

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

Synopsis:

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

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

In this example, the @code{\ref@{popular@}} produces @samp{2}.  Note
that it is a forward reference since it comes before
@code{\label@{popular@}}.

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


@node Environments
@chapter Environments

@cindex environments
@findex \begin
@findex \end

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

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

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

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

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


@node abstract
@section @code{abstract}

@EnvIndex{abstract}
@cindex abstracts

Synopsis:

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

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

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

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

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

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


@node array
@section @code{array}

@EnvIndex{array}
@cindex arrays, math

Synopsis:

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

or

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

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

The required argument @var{cols} describes the number of columns, their
alignment, and the formatting of the intercolumn regions.  See
@ref{tabular} for the complete description of @var{cols}, and of the
other common features of the two environments, including the optional
@var{pos} argument.

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

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

Here is an example of an array:

@example
\begin@{equation@}
  \begin@{array@}@{cr@}
    \sqrt@{y@}  &12.3 \\
    x^2       &3.4       
  \end@{array@}
\end@{equation@}
@end example

The next example works if @code{\usepackage@{amsmath@}} is in the
preamble:

@example
\begin@{equation@}
  \begin@{vmatrix@}@{cc@}
    a  &b \\
    c  &d       
  \end@{vmatrix@}=ad-bc
\end@{equation@}
@end example


@node center
@section @code{center}

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

Synopsis:

@example
\begin@{center@}
  ... text ...
\end@{center@}
@end example

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

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

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

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

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

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

A double backslash after the final line is optional.

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


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

@findex \centering
@cindex centering text, declaration for

A declaration that causes material in its scope to be centered.  It is
most often used inside an environment such as @code{figure}, or in a
@code{parbox}.

Unlike the @code{center} environment, the @code{\centering} command does
not add vertical space above and below the text.

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

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

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

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


@node description
@section @code{description}

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

Synopsis:

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

Environment to make a labelled list of items.  Each item's @var{label}
is typeset in bold, flush-left.  Each item's text may contain multiple
paragraphs.  Although the labels on the items are optional there is no
sensible default, so all items should have labels.

@findex \item
The list consists of at least one item, created with the @code{\item}
command (@pxref{\item}).  Having no items causes the @LaTeX{} error
@samp{Something's wrong--perhaps a missing \item}).

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

For other major @LaTeX{} labelled list environments, see @ref{itemize}
and @ref{enumerate}.  For information about customizing list layout, see
@ref{list}; also, the package @file{enumitem} is useful for this.

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

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


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

@EnvIndex{displaymath}

Synopsis:

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

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

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

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

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

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

The output from this example is centered and alone on its line. 
@example
\begin@{displaymath@}
  \int_1^2 x^2\,dx=7/3
\end@{displaymath@}
@end example
Also, the integral sign is larger than the inline version  
@code{\( \int_1^2 x^2\,dx=7/3 \)} produces.


@node document
@section @code{document}

@EnvIndex{document}

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

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


@node \AtBeginDocument

@findex \AtBeginDocument
@cindex beginning of document hook

Synopsis:

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

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

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


@node \AtEndDocument

@findex \AtEndDocument
@cindex end of document hook

Synopsis:

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

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

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


@node enumerate
@section @code{enumerate}

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

Synopsis:

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

Environment to produce a numbered list of items.  The format of the
label numbering depends on whether this environment is nested within
another; see below.

@findex \item
The list consists of at least one item.  Having no items causes the
@LaTeX{} error @samp{Something's wrong--perhaps a missing \item}.  Each
item is produced with an @code{\item} command.

This example lists the top two finishers in the 1908 Olympic marathon.

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

Enumerations may be nested within a paragraph-making environment,
including @code{itemize} (@pxref{itemize}), @code{description}
(@pxref{description}) and @code{enumeration}, up to four levels deep.
The format of the label produced depends on the place in the nesting.
This gives @LaTeX{}'s default for the format at each nesting level
(where 1 is the outermost level):

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

@findex \enumi
@findex \enumii
@findex \enumiii
@findex \enumiv
The @code{enumerate} environment uses the counters @code{\enumi} through
@code{\enumiv} counters (@pxref{Counters}).  If you use the optional
argument to @code{\item} then the counter is not incremented for that
item (@pxref{\item}).

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

@findex \Alph @r{example}
@example
\renewcommand@{\labelenumi@}@{\textbf@{\Alph@{enumi@}@}@}
\begin@{enumerate@}
  \item eI
  \item bi:
  \item si:
\end@{enumerate@}
@end example

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

For more on customizing the layout see @ref{list}.  Also, the package
@file{enumitem} is useful for this.



@node eqnarray
@section @code{eqnarray}

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

@cindex align @r{environment, from @code{amsmath}}
@cindex amsmath @r{package, replacing @code{eqnarray}}
@cindex Madsen, Lars
First, a caveat: the @code{eqnarray} environment is depreciated.  It has
infelicities that cannot be overcome, including spacing that is
inconsistent with other mathematics elements (see the article ``Avoid
eqnarray!''@: by Lars Madsen
@url{http://tug.org/TUGboat/tb33-1/tb103madsen.pdf}).  New documents
should include the @file{amsmath} package and use the displayed
mathematics environments provided there, such as the @code{align}
environment.

Nevertheless, for completeness and for a reference when working with old
documents, a synopsis:

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

or 

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

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

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

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

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

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

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


@node equation
@section @code{equation}

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

Synopsis:

@example
\begin@{equation@}
  math text
\end@{equation@}
@end example

Make a @code{displaymath} environment (@pxref{displaymath}) with an
equation number in the right margin.

The equation number is generated using the @code{equation} counter.

Note that the @file{amsmath} package has extensive displayed equation
facilities.  Those facilities are the best approach for such output in
new documents.


@node figure
@section @code{figure}

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

Synopsis:

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

or

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

A class of floats (@pxref{Floats}).  Because they cannot be split across
pages, they are not typeset in sequence with the normal text but instead
are ``floated'' to a convenient place, such as the top of a following
page.

For the possible values of @var{placement} and their effect on the 
float placement algorithm, see @ref{Floats}.

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

The figure body is typeset in a @code{parbox} of width @code{\textwidth}
and so it can contain text, commands, etc.

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

This example makes a figure out of a graphic.  It requires one of the
packages @file{graphics} or @file{graphicx}.  The graphic, with its
caption, will be placed at the top of a page or, if it is pushed to the
end of the document, on a page of floats.

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


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

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

Synopsis:

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

or

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

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

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

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

For example, this document

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

produces this file @file{JH.sty}.

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


@node flushleft
@section @code{flushleft}

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

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

@findex \\ @r{for @code{flushleft}}
The @code{flushleft} environment allows you to create a paragraph
consisting of lines that are flush to the left-hand margin and ragged
right. Each line must be terminated with the string @code{\\}.

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


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

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

The @code{\raggedright} declaration corresponds to the
@code{flushleft} environment.  This declaration can be used inside an
environment such as @code{quote} or in a @code{parbox}.

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


@node flushright
@section @code{flushright}

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

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

@findex \\ (for @code{flushright})
The @code{flushright} environment allows you to create a paragraph
consisting of lines that are flush to the right-hand margin and ragged
left.  Each line must be terminated with the control sequence @code{\\}.

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


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

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

The @code{\raggedleft} declaration corresponds to the
@code{flushright} environment.  This declaration can be used inside an
environment such as @code{quote} or in a @code{parbox}.

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


@node itemize
@section @code{itemize}

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

Synopsis:

@example
\begin@{itemize@}
\item @var{item1}
\item @var{item2}
...
\end@{itemize@}
@end example

The @code{itemize} environment produces an ``unordered'', ``bulleted''
list.  Itemized lists can be nested within one another, up to four
levels deep.  They can also be nested within other paragraph-making
environments, such as @code{enumerate} (@pxref{enumerate}).

Each item of an @code{itemize} list begins with an @code{\item} command.
There must be at least one @code{\item} command within the environment.

By default, the marks at each level look like this:

@enumerate
@item @bullet{} (bullet)
@item @b{-@w{-}} (bold en-dash)
@item * (asterisk)
@iftex
@item @math{\cdot} (centered dot)
@end iftex
@ifnottex
@item . (centered dot, rendered here as a period)
@end ifnottex
@end enumerate

@findex \labelitemi
@findex \labelitemii
@findex \labelitemiii
@findex \labelitemiv
The @code{itemize} environment uses the commands @code{\labelitemi}
through @code{\labelitemiv} to produce the default label.  So, you can
use @code{\renewcommand} to change the labels.  For instance, to have
the first level use diamonds:

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

@findex \leftmargin
@findex \leftmargini
@findex \leftmarginii
@findex \leftmarginiii
@findex \leftmarginiv
@findex \leftmarginv
@findex \leftmarginvi
The @code{\leftmargini} through @code{\leftmarginvi} parameters define
the distance between the left margin of the enclosing environment and
the left margin of the list.  By convention, @code{\leftmargin} is set
to the appropriate @code{\leftmargin@var{N}} when a new level of
nesting is entered.

The defaults vary from @samp{.5em} (highest levels of nesting) to
@samp{2.5em} (first level), and are a bit reduced in two-column mode.
This example greatly reduces the margin space for outermost lists:

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

@c xx should be in its own generic section
Some parameters that affect list formatting:

@ftable @code
@item \itemindent
Extra indentation before each item in a list; default zero.

@item \labelsep
Space between the label and text of an item; default @samp{.5em}.

@item \labelwidth
Width of the label; default @samp{2em}, or @samp{1.5em} in two-column mode.

@item \listparindent
Extra indentation added to second and subsequent paragraphs within a
list item; default @samp{0pt}.

@item \rightmargin
Horizontal distance between the right margin of the list and the
enclosing environment; default @samp{0pt}, except in the @code{quote},
@code{quotation}, and @code{verse} environments, where it is set equal
to @code{\leftmargin}.

@end ftable

Parameters affecting vertical spacing between list items (rather
loose, by default).

@ftable @code
@item \itemsep
Vertical space between items.  The default is @code{2pt plus1pt
minus1pt} for @code{10pt} documents, @code{3pt plus2pt minus1pt} for
@code{11pt}, and @code{4.5pt plus2pt minus1pt} for @code{12pt}.

@item \parsep
Extra vertical space between paragraphs within a list item.  Defaults
are the same as @code{\itemsep}.

@item \topsep
Vertical space between the first item and the preceding paragraph.
For top-level lists, the default is @code{8pt plus2pt minus4pt} for
@code{10pt} documents, @code{9pt plus3pt minus5pt} for @code{11pt},
and @code{10pt plus4pt minus6pt} for @code{12pt}.  These are reduced
for nested lists.

@item \partopsep
Extra space added to @code{\topsep} when the list environment starts a
paragraph.  The default is @code{2pt plus1pt minus1pt} for @code{10pt}
documents, @code{3pt plus1pt minus1pt} for @code{11pt}, and @code{3pt
plus2pt minus2pt} for @code{12pt}.

@end ftable

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

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


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

@EnvIndex{letter}

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


@node list
@section @code{list}

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

The @code{list} environment is a generic environment which is used for
defining many of the more specific environments. It is seldom used in
documents, but often in macros.

@example
\begin@{list@}@{@var{labeling}@}@{@var{spacing}@}
\item @var{item1}
\item @var{item2}
...
\end@{list@}
@end example

The mandatory @var{labeling} argument specifies how items should be
labelled (unless the optional argument is supplied to @code{\item}).
This argument is a piece of text that is inserted in a box to form the
label.  It can and usually does contain other @LaTeX{} commands.

The mandatory @var{spacing} argument contains commands to change the
spacing parameters for the list.  This argument will most often be
empty, i.e., @code{@{@}}, which leaves the default spacing.

The width used for typesetting the list items is specified by
@code{\linewidth} (@pxref{Page layout parameters}).

@menu
* \item::          An entry in a list.
@end menu


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

Synopsis:

@example
\item text of item
@end example

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

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

Because the optional argument @var{optional label} is surrounded by
square brackets@tie{}(@code{[} and @code{]}), to use square brackets
inside the optional argument you must hide them inside curly braces, as
in @code{\item[Close square bracket, @{]@}]}.  Similarly, to use an open
square bracket as first character in the text of the item, also hide it
inside curly braces.  @xref{@LaTeX{} command syntax}.

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

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

The first item is labelled @samp{1.}, the second item is labelled
@samp{sometimes}, and the third item is labelled @samp{2.} (note that,
because of the optional label in the second item, the third item does
not get a @samp{3.}).
   


@node math
@section @code{math}

@EnvIndex{math}
@cindex in-line formulas

Synopsis:

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

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


@node minipage
@section @code{minipage}

@EnvIndex{minipage}
@cindex minipage, creating a

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

The @code{minipage} environment typesets its body @var{text} in a
block that will not be broken across pages.  This is similar to the
@code{\parbox} command (@pxref{\parbox}), but unlike @code{\parbox},
other paragraph-making environments can be used inside a minipage.

@c (xxref positions)
The arguments are the same as for @code{\parbox} (@pxref{\parbox}).

@cindex indentation of paragraphs, in minipage
@cindex paragraph indentation, in minipage
@findex \parindent
By default, paragraphs are not indented in the @code{minipage}
environment.  You can restore indentation with a command such as
@code{\setlength@{\parindent@}@{1pc@}} command.

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

However, don't put one minipage inside another if you are using
footnotes; they may wind up at the bottom of the wrong minipage.


@node picture
@section @code{picture}

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

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

@findex \unitlength
The @code{picture} environment allows you to create just about any
kind of picture you want containing text, lines, arrows and circles.
You tell @LaTeX{} where to put things in the picture by specifying
their coordinates.  A coordinate is a number that may have a decimal
point and a minus sign---a number like @code{5}, @code{0.3} or
@code{-3.1416}.  A coordinate specifies a length in multiples of the
unit length @code{\unitlength}, so if @code{\unitlength} has been set
to @code{1cm}, then the coordinate 2.54 specifies a length of 2.54
centimeters.

You should only change the value of @code{\unitlength}, using the
@code{\setlength} command, outside of a @code{picture} environment.
The default value is @code{1pt}.

@PkgIndex{picture}
The @code{picture} package redefine the @code{picture} environment so
that everywhere a number is used in a @var{picture commands} to specify
a coordinate, one can use alternatively a length. Be aware however that
this will prevent scaling those lengths by changing @code{\unitlength}.


@cindex position, in picture
A @dfn{position} is a pair of coordinates, such as @code{(2.4,-5)}, specifying
the point with x-coordinate @code{2.4} and y-coordinate @code{-5}.
Coordinates are specified in the usual way with respect to an origin,
which is normally at the lower-left corner of the picture.  Note that
when a position appears as an argument, it is not enclosed in braces;
the parentheses serve to delimit the argument.

The @code{picture} environment has one mandatory argument which is a
position (@var{width},@var{height}), which specifies the size of the
picture.  The environment produces a rectangular box with these
@var{width} and @var{height}.

The @code{picture} environment also has an optional position argument
(@var{xoffset},@var{yoffset}), following the size argument, that can
change the origin.  (Unlike ordinary optional arguments, this argument
is not contained in square brackets.) The optional argument gives the
coordinates of the point at the lower-left corner of the picture
(thereby determining the origin).  For example, if @code{\unitlength}
has been set to @code{1mm}, the command

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

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

The environment's mandatory argument determines the nominal size of the
picture.  This need bear no relation to how large the picture really is;
@LaTeX{} will happily allow you to put things outside the picture, or even
off the page.  The picture's nominal size is used by @LaTeX{} in determining
how much room to leave for it.

Everything that appears in a picture is drawn by the @code{\put}
command. The command

@example
\put (11.3,-.3)@{...@}
@end example

@noindent puts the object specified by @code{...} in the
picture, with its reference point at coordinates @math{(11.3,-.3)}.
The reference points for various objects will be described below.

@findex lR box
The @code{\put} command creates an @dfn{LR box}.  You can put anything
that can go in an @code{\mbox} (@pxref{\mbox}) in the text argument of
the @code{\put} command.  When you do this, the reference point will
be the lower left corner of the box.

The @code{picture} commands are described in the following sections.

@menu
* \circle::             Draw a circle.
* \makebox (picture)::  Draw a box of the specified size.
* \framebox (picture):: Draw a box with a frame around it.
* \dashbox::            Draw a dashed box.
* \frame::              Draw a frame around an object.
* \line::               Draw a straight line.
* \linethickness::      Set the line thickness.
* \thicklines::         A heavier line thickness.
* \thinlines::          The default line thickness.
* \multiput::           Draw multiple instances of an object.
* \oval::               Draw an ellipse.
* \put::                Place an object at a specified place.
* \shortstack::         Make a pile of objects.
* \vector::             Draw a line with an arrow.
@end menu


@node \circle
@subsection @code{\circle}

@findex \circle

Synopsis:

@example
\circle[*]@{@var{diameter}@}
@end example

The @code{\circle} command produces a circle with a diameter as close
to the specified one as possible.  The @code{*}-form of the command
draws a solid circle.

Circles up to 40@dmn{pt} can be drawn.


@node \makebox (picture)
@subsection @code{\makebox}

@findex \makebox @r{(for @code{picture})}

Synopsis:

@example
\makebox(@var{width},@var{height})[@var{position}]@{@var{text}@}
@end example

The @code{\makebox} command for the picture environment is similar to
the normal @code{\makebox} command except that you must specify a
@var{width} and @var{height} in multiples of @code{\unitlength}.

The optional argument, @code{[@var{position}]}, specifies the quadrant that
your @var{text} appears in.  You may select up to two of the following:

@table @code
@item t
Moves the item to the top of the rectangle.

@item b
Moves the item to the bottom.

@item l
Moves the item to the left.

@item r
Moves the item to the right.

@end table

@xref{\makebox}.


@node \framebox (picture)
@subsection @code{\framebox}

@findex \framebox

Synopsis:

@example
\framebox(@var{width},@var{height})[@var{pos}]@{...@}
@end example

The @code{\framebox} command is like @code{\makebox} (see previous
section), except that it puts a frame around the outside of the box
that it creates.

@findex \fboxrule
@findex \fboxsep
The @code{\framebox} command produces a rule of thickness
@code{\fboxrule}, and leaves a space @code{\fboxsep} between the rule
and the contents of the box.


@node \dashbox
@subsection @code{\dashbox}

@findex \dashbox

Draws a box with a dashed line.  Synopsis:

@example
\dashbox@{@var{dlen}@}(@var{rwidth},@var{rheight})[@var{pos}]@{@var{text}@}
@end example

@code{\dashbox} creates a dashed rectangle around @var{text} in a
@code{picture} environment.  Dashes are @var{dlen} units long, and the
rectangle has overall width @var{rwidth} and height @var{rheight}.
The @var{text} is positioned at optional @var{pos}.  @c xxref positions.

A dashed box looks best when the @var{rwidth} and @var{rheight} are
multiples of the @var{dlen}.


@node \frame
@subsection @code{\frame}

@findex \frame

Synopsis:

@example
\frame@{@var{text}@}
@end example

The @code{\frame} command puts a rectangular frame around @var{text}.
The reference point is the bottom left corner of the frame.  No extra
space is put between the frame and the object.


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

@findex \line

Synopsis:

@example
\line(@var{xslope},@var{yslope})@{@var{length}@}
@end example

The @code{\line} command draws a line with the given @var{length} and
slope @var{xslope}/@var{yslope}.

@cindex @code{pict2e} package
@cindex graphics packages
Standard @LaTeX{} can only draw lines with @math{@var{slope} = x/y},
where @math{x} and @math{y} have integer values from @minus{}6
through@tie{}6.  For lines of any slope, and plenty of other shapes,
see @code{pict2e} and many other packages on CTAN.


@node \linethickness
@subsection @code{\linethickness}

@findex \linethickness

The @code{\linethickness@{@var{dim}@}} command declares the thickness
of horizontal and vertical lines in a picture environment to be
@var{dim}, which must be a positive length.

@code{\linethickness} does not affect the thickness of slanted lines,
circles, or the quarter circles drawn by @code{\oval}.


@node \thicklines
@subsection @code{\thicklines}

@findex \thicklines

The @code{\thicklines} command is an alternate line thickness for
horizontal and vertical lines in a picture environment;
cf.@tie{}@ref{\linethickness} and @ref{\thinlines}.


@node \thinlines
@subsection @code{\thinlines}

@findex \thinlines

The @code{\thinlines} command is the default line thickness for
horizontal and vertical lines in a picture environment;
cf.@tie{}@ref{\linethickness} and @ref{\thicklines}.


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

@findex \multiput

Synopsis:

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

The @code{\multiput} command copies the object @var{obj} in a regular
pattern across a picture.  @var{obj} is first placed at position
@math{(x,y)}, then at @math{(x+\delta x,y+\delta y)}, and so on,
@var{n} times.


@node \oval
@subsection @code{\oval}

@findex \oval

Synopsis:

@example
\oval(@var{width},@var{height})[@var{portion}]
@end example

The @code{\oval} command produces a rectangle with rounded corners.  The
optional argument @var{portion} allows you to produce only half of the
oval via the following:

@table @code
@item t
selects the top half;
@item b
selects the bottom half;
@item r
selects the right half;
@item l
selects the left half.
@end table

It is also possible to produce only one quarter of the oval by setting
@var{portion} to @code{tr}, @code{br}, @code{bl}, or @code{tl}.

The ``corners'' of the oval are made with quarter circles with a
maximum radius of 20@dmn{pt}, so large ``ovals'' will look more like
boxes with rounded corners.


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

@findex \put

Synopsis:

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

The @code{\put} command places the material specified by the
(mandatory) argument in braces at the given coordinate,
(@var{xcoord},@var{ycoord}).


@node \shortstack
@subsection @code{\shortstack}

@findex \shortstack

Synopsis:

@example
\shortstack[@var{position}]@{...\\...\\...@}
@end example

The @code{\shortstack} command produces a stack of objects.  The valid
positions are:

@table @code
@item r
Move the objects to the right of the stack.
@item l
Move the objects to the left of the stack
@item c
Move the objects to the centre of the stack (default)
@end table

@findex \\ @r{(for @code{\shortstack} objects)}
Objects are separated with @code{\\}.


@node \vector
@subsection @code{\vector}

@findex \vector

Synopsis:

@example
\vector(@var{xslope},@var{yslope})@{@var{length}@}
@end example

The @code{\vector} command draws a line with an arrow of the specified
length and slope.  The @math{@var{xslope}} and @math{@var{yslope}}
values must lie between @minus{}4 and +4, inclusive.


@node quotation and quote
@section @code{quotation} and @code{quote}

@EnvIndex{quotation}
@cindex quoted text with paragraph indentation, displaying
@cindex displaying quoted text with paragraph indentation
@cindex paragraph indentations in quoted text
@EnvIndex{quote}
@cindex quoted text without paragraph indentation, displaying
@cindex displaying quoted text without paragraph indentation
@cindex paragraph indentations in quoted text, omitting

Synopsis:

@example
\begin@{quotation@}
@var{text}
\end@{quotation@}
@end example

or 

@example
\begin@{quote@}
@var{text}
\end@{quote@}
@end example

Include a quotation. 

In both environments, margins are indented on both sides by
@code{\leftmargin} and the text is justified at both.  As with the main
text, leaving a blank line produces a new paragraph.

To compare the two: in the @code{quotation} environment, paragraphs are
indented by 1.5@dmn{em} and the space between paragraphs is small,
@code{0pt plus 1pt}.  In the @code{quote} environment, paragraphs are
not indented and there is vertical space between paragraphs (it is the
rubber length @code{\parsep}).  Thus, the @code{quotation} environment
may be more suitable for documents where new paragraphs are marked by an
indent rather than by a vertical separation.  In addition, @code{quote}
may be more suitable for a short quotation or a sequence of short
quotations.

@example
\begin@{quotation@}
\it Four score and seven years ago
  ... shall not perish from the earth.
\hspace@{1em plus 1fill@}---Abraham Lincoln
\end@{quotation@}
@end example


@node tabbing
@section @code{tabbing}

@EnvIndex{tabbing}
@cindex tab stops, using
@cindex lining text up using tab stops
@cindex alignment via tabbing

Synopsis:

@example
\begin@{tabbing@}
@var{row1col1} \= @var{row1col2} \= @var{row1col3} \= @var{row1col4} \\
@var{row2col1} \>                \> @var{row2col3} \\
...
\end@{tabbing@}
@end example

The @code{tabbing} environment provides a way to align text in
columns.  It works by setting tab stops and tabbing to them much as
was done on an ordinary typewriter.  It is best suited for cases where
the width of each column is constant and known in advance.

This environment can be broken across pages, unlike the @code{tabular}
environment.

The following commands can be used inside a @code{tabbing} environment:

@ftable @code
@item \\ @r{(tabbing)}
End a line.

@item \= @r{(tabbing)}
Sets a tab stop at the current position.

@item \> @r{(tabbing)}
@findex \>
Advances to the next tab stop.

@item \<
Put following text to the left of the local margin (without changing
the margin).  Can only be used at the start of the line.

@item \+
Moves the left margin of the next and all the
following commands one tab stop to the right, beginning tabbed line if
necessary.

@item \-
Moves the left margin of the next and all the
following commands one tab stop to the left, beginning tabbed line if
necessary.

@item \' @r{(tabbing)}
Moves everything that you have typed so far in the
current column, i.e., everything from the most recent @code{\>},
@code{\<}, @code{\'}, @code{\\}, or @code{\kill} command, to the right
of the previous column, flush against the current column's tab stop.

@item \` @r{(tabbing)}
Allows you to put text flush right against any tab stop, including tab
stop@tie{}0.  However, it can't move text to the right of the last column
because there's no tab stop there.  The @code{\`} command moves all the
text that follows it, up to the @code{\\} or @code{\end@{tabbing@}}
command that ends the line, to the right margin of the tabbing
environment.  There must be no @code{\>} or @code{\'} command between
the @code{\`} and the command that ends the line.

@item \a @r{(tabbing)}
@findex \a' @r{(acute accent in tabbing)}
@findex \a` @r{(grave accent in tabbing)}
@findex \a= @r{(macron accent in tabbing)}
In a @code{tabbing} environment, the commands @code{\=}, @code{\'} and
@code{\`} do not produce accents as usual (@pxref{Accents}).  Instead,
the commands @code{\a=}, @code{\a'} and @code{\a`} are used.

@item \kill
Sets tab stops without producing text.  Works just like @code{\\}
except that it throws away the current line instead of producing
output for it.  The effect of any @code{\=}, @code{\+} or @code{\-}
commands in that line remain in effect.

@item \poptabs
@findex \poptabs
Restores the tab stop positions saved by the last @code{\pushtabs}.

@item \pushtabs
Saves all current tab stop positions. Useful for temporarily changing
tab stop positions in the middle of a @code{tabbing} environment.

@item \tabbingsep
Distance to left of tab stop moved by @code{\'}.

@end ftable

This example typesets a Pascal function in a traditional format:

@example
\begin@{tabbing@}
function \= fact(n : integer) : integer;\\
         \> begin \= \+ \\
               \> if \= n $>$ 1 then \+ \\
                        fact := n * fact(n-1) \- \\
                  else \+ \\
                        fact := 1; \-\- \\
            end;\\
\end@{tabbing@}
@end example


@node table
@section @code{table}

@EnvIndex{table}
@cindex tables, creating
@cindex creating tables

Synopsis:

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

A class of floats (@pxref{Floats}).  Because they cannot be split across
pages, they are not typeset in sequence with the normal text but instead
are ``floated'' to a convenient place, such as the top of a following
page.

For the possible values of @var{placement} and their effect on the 
float placement algorithm, see @ref{Floats}.

The table body is typeset in a @code{parbox} of width @code{\textwidth}
and so it can contain text, commands, etc.

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

In this example the table and caption will float to the bottom of a page,
unless it is pushed to a float page at the end.

@example
\begin@{table@}[b]
  \centering
  \begin@{tabular@}@{r|p@{2in@}@} \hline
    One &The loneliest number \\
    Two &Can be as sad as one.
         It's the loneliest number since the number one.
  \end@{tabular@}
  \caption@{Cardinal virtues@}
  \label@{tab:CardinalVirtues@}
\end@{table@}
@end example 


@node tabular
@section @code{tabular}

@EnvIndex{tabular}
@cindex lines in tables
@cindex lining text up in tables

Synopsis:

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

@noindent
or

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

These environments produce a table, a box consisting of a sequence of
horizontal rows.  Each row consists of items that are aligned vertically
in columns.  This illustrates many of the features.

@example
\begin@{tabular@}@{l|l@}
  \textit@{Player name@}  &\textit@{Career home runs@}  \\ 
  \hline
  Hank Aaron  &755 \\
  Babe Ruth   &714
\end@{tabular@}
@end example

The vertical format of two left-aligned columns, with a vertical bar
between them, is specified in @code{tabular}'s argument @code{@{l|l@}}.
@findex & 
Columns are separated with an ampersand @code{&}.  A horizontal rule
between two rows is created with @code{\hline}.
@findex \\ @r{for @code{tabular}}
The end of each row is marked with a double backslash@tie{}@code{\\}.
This @code{\\} is optional after the last row unless an @code{\hline}
command follows, to put a rule below the table.

The required and optional arguments to @code{tabular} consist of:

@table @var
@item width
Required for @code{tabular*}, not allowed for @code{tabular}. Specifies
the width of the @code{tabular*} environment.  The space between columns
should be rubber, as with @code{@@@{\extracolsep@{\fill@}@}}, to allow
the table to stretch or shrink to make the specified width, or else you
are likely to get the @code{Underfull \hbox (badness 10000) in alignment
...} warning.

@item pos
Optional.  Specifies the table's vertical position.  The default is to
align the table so its vertical center matches the baseline of the
surrounding text.  There are two other possible alignments: @code{t}
aligns the table so its top row matches the baseline of the surrounding
text, and @code{b} aligns on the bottom row.

This only has an effect if there is other text.  In the common case of a
@code{tabular} alone in a @code{center} environment this option makes
no difference.

@item cols
Required.  Specifies the formatting of columns.  It consists of a
sequence of the following specifiers, corresponding to the types of
column and intercolumn material.

@table @code
@item l
A column of left-aligned items.

@item r
A column of right-aligned items.

@item c
A column of centered items.

@item |
A vertical line the full height and depth of the environment.

@item @@@{@var{text or space}@}
This inserts @var{text or space} at this location in every row.  The
@var{text or space} material is typeset in LR mode.  This text is
fragile (@pxref{\protect}).

This specifier is optional: with no @@-expression, @LaTeX{}'s
@code{book}, @code{article}, and @code{report} classes will put on
either side of each column a space of length @code{\tabcolsep}, which
by default is @samp{6pt}.  That is, by default adjacent columns are
separated by 12pt (so @code{\tabcolsep} is misleadingly-named since it
is not the separation between tabular columns).  By implication, a
space of 6pt also comes before the first column and after the final
column, unless you put a @code{@@@{...@}} or @code{|} there.

If you override the default and use an @@-expression then you must
insert any desired space yourself, as in @code{@@@{\hspace@{1em@}@}}.

An empty expression @code{@@@{@}} will eliminate the space, including
the space at the start or end, as in the example below where the tabular
lines need to lie on the left margin.

@example
\begin@{flushleft@}
  \begin@{tabular@}@{@@@{@}l@}
    ...
  \end@{tabular@}
\end@{flushleft@}
@end example

This example shows text, a decimal point, between the columns, arranged
so the numbers in the table are aligned on that decimal point.

@example 
\begin@{tabular@}@{r@@@{$.$@}l@}
  $3$ &$14$  \\
  $9$ &$80665$
\end@{tabular@}
@end example

@findex \extracolsep
An @code{\extracolsep@{@var{wd}@}} command in an @@-expression causes an
extra space of width @var{wd} to appear to the left of all subsequent
columns, until countermanded by another @code{\extracolsep} command.
Unlike ordinary intercolumn space, this extra space is not suppressed by
an @@-expression.  An @code{\extracolsep} command can be used only in an
@@-expression in the @code{cols} argument.  Below, @LaTeX{} inserts the
right amount of intercolumn space to make the entire table 4 inches
wide.

@example
\begin@{center@}
  \begin@{tabular*@}@{4in@}@{l@@@{\ \ldots\extracolsep@{\fill@}@}l@}
    Seven times down, eight times up 
    &such is life!
  \end@{tabular*@}
\end@{center@}
@end example

To insert commands that are automatically executed before a given
column, load the @code{array} package and use the @code{>@{...@}}
specifier.
@c xx should fully explain array, tabularx, and all other base packages...

@item p@{@var{wd}@}
Each item in the column is typeset in a parbox of width @var{wd}.

Note that a line break double backslash @code{\\} may not appear in the
item, except inside an environment like @code{minipage}, @code{array},
or @code{tabular}, or inside an explicit @code{\parbox}, or in the scope
of a @code{\centering}, @code{\raggedright}, or @code{\raggedleft}
declaration (when used in a @code{p}-column element these declarations
must appear inside braces, as with @code{@{\centering .. \\
..@}}). Otherwise @LaTeX{} will misinterpret the double backslash as
ending the row.

@item *@{@var{num}@}@{@var{cols}@}
Equivalent to @var{num} copies of @var{cols}, where @var{num} is a
positive integer and @var{cols} is a list of specifiers.  Thus
@code{\begin@{tabular@}@{|*@{3@}@{l|r@}|@}} is equivalent to
@code{\begin@{tabular@}@{|l|rl|rl|r|@}}.  Note that @var{cols} may
contain another @code{*}-expression.
 
@end table
@end table

Parameters that control formatting:
@c xx defaults, own node (xref from array)?

@ftable @code
@item \arrayrulewidth
A length that is the thickness of the rule created by @code{|},
@code{\hline}, and @code{\vline} in the @code{tabular} and @code{array}
environments.  The default is @samp{.4pt}. Change it as in
@code{\setlength@{\arrayrulewidth@}@{0.8pt@}}.

@item \arraystretch
A factor by which the spacing between rows in the @code{tabular} and
@code{array} environments is multiplied.  The default is @samp{1}, for
no scaling.  Change it as @code{\renewcommand@{\arraystretch@}@{1.2@}}.

@item \doublerulesep
A length that is the distance between the vertical rules produced by the
@code{||} specifier.  The default is @samp{2pt}.

@item \tabcolsep
A length that is half of the space between columns. The default is
@samp{6pt}.  Change it with @code{\setlength}.

@end ftable

The following commands can be used inside the body of a @code{tabular}
environment, the first two inside an entry and the second two between
lines:

@menu
* \multicolumn::        Make an item spanning several columns.
* \vline::              Draw a vertical line.
* \cline::              Draw a horizontal line spanning some columns.
* \hline::              Draw a horizontal line spanning all columns.
@end menu


@node \multicolumn
@subsection @code{\multicolumn}

@findex \multicolumn

Synopsis:

@example
\multicolumn@{@var{numcols}@}@{@var{cols}@}@{@var{text}@}
@end example

Make an @code{array} or @code{tabular} entry that spans several columns.
The first argument @var{numcols} gives the number of columns to span.
The second argument @var{cols} specifies the formatting of the entry,
with @code{c} for centered, @code{l} for flush left, or @code{r} for
flush right.  The third argument @var{text} gives the contents of that
entry.

In this example, in the first row, the second and third columns are
spanned by the single heading @samp{Name}.

@example
\begin@{tabular@}@{lccl@} 
  \textit@{ID@}       &\multicolumn@{2@}@{c@}@{\textit@{Name@}@} &\textit@{Age@} \\ \hline % row one 
  978-0-393-03701-2 &O'Brian &Patrick                  &55           \\        % row two 
    ...
\end@{tabular@}
@end example

What counts as a column is:@tie{}the column format specifier for the
@code{array} or @code{tabular} environment is broken into parts, where
each part (except the first) begins with @code{l}, @code{c}, @code{r},
or@tie{}@code{p}.  So from @code{\begin@{tabular@}@{|r|ccp@{1.5in@}|@}}
the parts are @code{|r|}, @code{c}, @code{c},
and@tie{}@code{p@{1.5in@}|}.

The @var{cols} argument overrides the @code{array} or @code{tabular}
environment's intercolumn area default adjoining this multicolumn
entry. To affect that area, this argument can contain vertical bars
@code{|} indicating the placement of vertical rules, and @code{@@@{...@}}
expressions.  Thus if @var{cols} is @samp{|c|} then this multicolumn
entry will be centered and a vertical rule will come in the intercolumn
area before it and after it.  This table details the exact behavior.

@example
\begin@{tabular@}@{|cc|c|c|@}
  \multicolumn@{1@}@{r@}@{w@}       % entry one
    &\multicolumn@{1@}@{|r|@}@{x@}  % entry two 
    &\multicolumn@{1@}@{|r@}@{y@}   % entry three
    &z                        % entry four
\end@{tabular@}
@end example

Before the first entry the output will not have a vertical rule because
the @code{\multicolumn} has the @var{cols} specifier @samp{r} with no
initial vertical bar.  Between entry one and entry two there will be a
vertical rule; although the first @var{cols} does not have an ending
vertical bar, the second @var{cols} does have a starting one.  Between
entry two and entry three there is a single vertical rule; despite that
the @var{cols} in both of the surrounding @code{multicolumn}'s call for
a vertical rule, you only get one rule.  Between entry three and entry
four there is no vertical rule; the default calls for one but the
@var{cols} in the entry three @code{\multicolumn} leaves it out, and
that takes precedence.  Finally, following entry four there is a
vertical rule because of the default.

The number of spanned columns @var{numcols} can be 1.  Besides giving
the ability to change the horizontal alignment, this also is useful to
override for one row the @code{tabular} definition's default intercolumn
area specification, including the placement of vertical rules.

In the example below, in the @code{tabular} definition the first column
is specified to default to left justified but in the first row the entry
is centered with @code{\multicolumn@{1@}@{c@}@{\textsc@{Period@}@}}.
Also in the first row, the second and third columns are spanned by a
single entry with @code{\multicolumn@{2@}@{c@}@{\textsc@{Span@}@}},
overriding the specification to center those two columns on the page
range en-dash.

@example
\begin@{tabular@}@{l|r@@@{--@}l@} 
  \multicolumn@{1@}@{c@}@{\textsc@{Period@}@}  
    &multicolumn@{2@}@{c@}@{\textsc@{Span@}@} \\ \hline
  Baroque          &1600           &1760         \\
  Classical        &1730           &1820         \\
  Romantic         &1780           &1910         \\
  Impressionistic  &1875           &1925
\end@{tabular@}
@end example

Note that although the @code{tabular} specification by default puts a
vertical rule between the first and second columns, because there is no
vertical bar in the @var{cols} of either of the first row's
@code{\multicolumn} commands, no rule appears in the first row.


@node \vline
@subsection @code{\vline}

@findex \vline
Draw a vertical line in a @code{tabular} or @code{array} environment
extending the full height and depth of an entry's row.  Can also be
used in an @@-expression, although its synonym vertical
bar@tie{}@code{|} is more common.  This command is rarely used in the
body of a table; typically a table's vertical lines are specified in
@code{tabular}'s @var{cols} argument and overridden as needed with
@code{\multicolumn}.

This example illustrates some pitfalls.  In the first line's second
entry the @code{\hfill} moves the @code{\vline} to the left edge of the
cell.  But that is different than putting it halfway between the two
columns, so in that row between the first and second columns there are
two vertical rules, with the one from the @code{@{c|cc@}} specifier
coming before the one produced by the @code{\vline\hfill}.  In contrast,
the first line's third entry shows the usual way to put a vertical bar
between two columns.  In the second line, the @code{ghi} is the widest
entry in its column so in the @code{\vline\hfill} the @code{\hfill} has
no effect and the vertical line in that entry appears immediately next
to the @code{g}, with no whitespace.

@example
\begin@{tabular@}@{c|cc@}
  x   &\vline\hfill y   &\multicolumn@{1@}@{|r@}@{z@} \\  
  abc &def &\vline\hfill ghi 
\end@{tabular@}
@end example


@node \cline
@subsection @code{\cline}

@findex \cline

Synopsis:

@example
\cline@{@var{i}-@var{j}@}
@end example

Draw a horizontal rule in an @code{array} or @code{tabular} environment
beginning in column @var{i} and ending in column @var{j}. The
dash@tie{}@code{-} must appear in the mandatory argument. To span a
single column use the number twice.

This example puts two horizontal lines between the first and second
rows, one line in the first column only, and the other spanning the
third and fourth columns.  The two lines are side-by-side, at the same
height.

@example
\begin@{tabular@}@{llrr@} 
  a &b &c &d \\ \cline@{1-1@} \cline@{3-4@} 
  e &f &g &h 
\end@{tabular@}
@end example


@node \hline
@subsection @code{\hline}

@findex \hline

Draws a horizontal line the width of the enclosing @code{tabular} or
@code{array} environment.  It's most commonly used to draw a line at the
top, bottom, and between the rows of a table.

In this example the top of the table has two horizontal rules, one above
the other, that span both columns.  The bottom of the table has a single
rule spanning both columns.  Because of the @code{\hline}, the
@code{tabular} second row's line ending double backslash@tie{}@code{\\}
is required.

@example
\begin@{tabular@}@{ll@} \hline\hline
  Baseball   &Red Sox  \\
  Basketball &Celtics  \\ \hline
\end@{tabular@}
@end example


@node thebibliography
@section @code{thebibliography}

@EnvIndex{thebibliography}
@cindex bibliography, creating (manually)

Synopsis:

@example
\begin@{thebibliography@}@{@var{widest-label}@}
\bibitem[@var{label}]@{@var{cite_key@}}
...
\end@{thebibliography@}
@end example

The @code{thebibliography} environment produces a bibliography or
reference list.

In the @code{article} class, this reference list is labelled
``References''; in the @code{report} class, it is labelled
``Bibliography''.  You can change the label (in the standard classes)
by redefining the command @code{\refname}.  For instance, this
eliminates it entirely:

@example
\renewcommand@{\refname@}@{@}
@end example

The mandatory @var{widest-label} argument is text that, when typeset,
is as wide as the widest item label produced by the @code{\bibitem}
commands.  It is typically given as @code{9} for bibliographies with
less than 10 references, @code{99} for ones with less than 100, etc.

@menu
* \bibitem::            Specify a bibliography item.
* \cite::               Refer to a bibliography item.
* \nocite::             Include an item in the bibliography.
* Using BibTeX::        Automatic generation of bibliographies.
@end menu


@node \bibitem
@subsection @code{\bibitem}

@findex \bibitem

Synopsis:

@example
\bibitem[@var{label}]@{@var{cite_key}@}
@end example

The @code{\bibitem} command generates an entry labelled by @var{label}.
If the @var{label} argument is missing, a number is automatically
generated using the @code{enumi} counter.  The @var{cite_key} is a
@cindex citation key
@dfn{citation key} consisting in any sequence of
letters, numbers, and punctuation symbols not containing a comma.

This command writes an entry to the @file{.aux} file containing the
item's @var{cite_key} and @var{label}.  When the @file{.aux} file is
read by the @code{\begin@{document@}} command, the item's @var{label} is
associated with @code{cite_key}, causing references to @var{cite_key}
with a @code{\cite} command (@pxref{\cite}) to produce the associated
@var{label}.


@node \cite
@subsection @code{\cite}

@findex \cite

Synopsis:

@example
\cite[@var{subcite}]@{@var{keys}@}
@end example

The @var{keys} argument is a list of one or more citation keys
(@pxref{\bibitem}), separated by commas.  This command generates an
in-text citation to the references associated with @var{keys} by entries
in the @file{.aux} file.

The text of the optional @var{subcite} argument appears after the
citation.  For example, @code{\cite[p.~314]@{knuth@}} might produce
@samp{[Knuth, p.@tie{}314]}.


@node \nocite
@subsection @code{\nocite}

@findex \nocite

Synopsis:

@example
@code{\nocite@{@var{keys}@}}
@end example

The @code{\nocite} command produces no text, but writes @var{keys},
which is a list of one or more citation keys, to the @file{.aux} file.


@node Using BibTeX
@subsection Using Bib@TeX{}

@cindex using Bib@TeX{}
@cindex bib@TeX{}, using
@cindex bibliography, creating (automatically)
@findex \bibliographystyle
@findex \bibliography

If you use the Bib@TeX{} program by Oren Patashnik (highly
recommended if you need a bibliography of more than a couple of
titles) to maintain your bibliography, you don't use the
@code{thebibliography} environment (@pxref{thebibliography}). Instead,
you include the lines

@example
\bibliographystyle@{@var{bibstyle}@}
\bibliography@{@var{bibfile1},@var{bibfile2}@}
@end example

The @code{\bibliographystyle} command does not produce any output of
its own.  Rather, it defines the style in which the bibliography will
be produced: @var{bibstyle} refers to a file
@var{bibstyle}@file{.bst}, which defines how your citations will look.
The standard @var{bibstyle} names distributed with Bib@TeX{} are:

@table @code
@item alpha
Sorted alphabetically. Labels are formed from name of author and year of
publication.
@item plain
Sorted alphabetically. Labels are numeric.
@item unsrt
Like @code{plain}, but entries are in order of citation.
@item abbrv
Like @code{plain}, but more compact labels.
@end table

In addition, numerous other Bib@TeX{} style files exist tailored to
the demands of various publications.  See
@url{http://mirror.ctan.org/biblio/bibtex/contrib}.

The @code{\bibliography} command is what actually produces the
bibliography.  The argument to @code{\bibliography} refers to files
named @file{@var{bibfile1}.bib}, @file{@var{bibfile2}.bib}, @dots{},
which should contain your database in
Bib@TeX{} format.  Only the entries referred to via @code{\cite} and
@code{\nocite} will be listed in the bibliography.


@node theorem
@section @code{theorem}

@EnvIndex{theorem}
@cindex theorems, typesetting

Synopsis:

@example
\begin@{theorem@}
@var{theorem-text}
\end@{theorem@}
@end example

The @code{theorem} environment produces ``Theorem @var{n}'' in
boldface followed by @var{theorem-text}, where the numbering
possibilities for @var{n} are described under @code{\newtheorem}
(@pxref{\newtheorem}).


@node titlepage
@section @code{titlepage}

@EnvIndex{titlepage}
@cindex making a title page
@cindex title pages, creating

Synopsis:

@example
\begin@{titlepage@}
  ... text and spacing ...
\end@{titlepage@}
@end example

Create a title page, a page with no printed page number or heading.  The
following page will be numbered page one.

To instead produce a standard title page without a @code{titlepage}
environment you can use @code{\maketitle} (@pxref{\maketitle}).

Notice in this example that all formatting, including vertical spacing,
is left to the author.

@example
\begin@{titlepage@}
\vspace*@{\stretch@{1@}@}
\begin@{center@}
  @{\huge\bfseries Thesis \\[1ex] 
                  title@}                  \\[6.5ex]
  @{\large\bfseries Author name@}           \\
  \vspace@{4ex@}
  Thesis  submitted to                    \\[5pt]
  \textit@{University name@}                \\[2cm]
  in partial fulfilment for the award of the degree of \\[2cm]
  \textsc@{\Large Doctor of Philosophy@}    \\[2ex]
  \textsc@{\large Mathematics@}             \\[12ex]
  \vfill
  Department of Mathematics               \\
  Address                                 \\
  \vfill
  \today
\end@{center@}
\vspace@{\stretch@{2@}@}
\end@{titlepage@}
@end example


@node verbatim
@section @code{verbatim}

@EnvIndex{verbatim}
@cindex verbatim text
@cindex simulating typed text
@cindex typed text, simulating
@cindex code, typesetting
@cindex computer programs, typesetting

Synopsis:

@example
\begin@{verbatim@}
@var{literal-text}
\end@{verbatim@}
@end example

The @code{verbatim} environment is a paragraph-making environment in
which @LaTeX{} produces exactly what you type in; for instance the
@code{\} character produces a printed @samp{\}.  It turns @LaTeX{}
into a typewriter with carriage returns and blanks having the same
effect that they would on a typewriter.

The @code{verbatim} uses a monospaced typewriter-like font (@code{\tt}).

@menu
* \verb::       The macro form of the @code{verbatim} environment.
@end menu

@node \verb
@subsection @code{\verb}

@findex \verb
@cindex verbatim text, inline

Synopsis:

@example
\verb@var{char}@var{literal-text}@var{char}
\verb*@var{char}@var{literal-text}@var{char}
@end example

The @code{\verb} command typesets @var{literal-text} as it is input,
including special characters and spaces, using the typewriter
(@code{\tt}) font.  No spaces are allowed between @code{\verb} or
@code{\verb*} and the delimiter @var{char}, which begins and ends the
verbatim text.  The delimiter must not appear in @var{literal-text}.

@cindex visible space
The @code{*}-form differs only in that spaces are printed with a
``visible space'' character.
@tex
(Namely, {\tt\char`\ }.)
@end tex


@node verse
@section @code{verse}

@EnvIndex{verse}
@cindex poetry, an environment for

Synopsis:

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

The @code{verse} environment is designed for poetry, though you may find
other uses for it.

@findex \\ @r{for @code{verse}}
The margins are indented on the left and the right, paragraphs are not
indented, and the text is not justified.  Separate the lines of each
stanza with @code{\\}, and use one or more blank lines to separate the
stanzas.


@node Line breaking
@chapter Line breaking

@cindex line breaking
@cindex breaking lines

The first thing @LaTeX{} does when processing ordinary text is to
translate your input file into a sequence of glyphs and spaces.  To
produce a printed document, this sequence must be broken into lines
(and these lines must be broken into pages).

@LaTeX{} usually does the line (and page) breaking in the text body for
you but in some environments you manually force line breaks.

@menu
* \\::                         Start a new line.
* \obeycr & \restorecr::       Make each input line start a new output line.
* \newline::                   Break the line
* \- (hyphenation)::           Insert explicit hyphenation.
* \discretionary::             Insert explicit hyphenation with control of hyphen character.
* \fussy::                     Be fussy about line breaking.
* \sloppy::                    Be sloppy about line breaking.
* \hyphenation::               Tell @LaTeX{} how to hyphenate a word.
* \linebreak & \nolinebreak::  Forcing & avoiding line breaks.
@end menu


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

@findex \\ @r{force line break}
@cindex new line, starting
@cindex line break, forcing

Synopsis:

@example
\\[@var{morespace}]
@end example

or 

@example
\\*[@var{morespace}]
@end example

Start a new line.  The optional argument @var{morespace} specifies extra
vertical space to be insert before the next line.  This can be a
negative length.  The text before the break is set at its normal length,
that is, it is not stretched to fill out the line width.

Explicit line breaks in the text body are unusual in @LaTeX{}.  In
particular, to start a new paragraph instead leave a blank line.  This
command is mostly used outside of the main flow of text such as in
a @code{tabular} or @code{array} environment.

Under ordinary circumstances (e.g., outside of a @code{p@{...@}} column
in a @code{tabular} environment) the @code{\newline} command is a synonym for
@code{\\} (@pxref{\newline}).

In addition to starting a new line, the starred form @code{\\*} tells
@LaTeX{} not to start a new page between the two lines, by issuing a
@code{\nobreak}.

@example
\title@{My story: \\[0.25in]
       a tale of woe@}
@end example


@node \obeycr & \restorecr
@section @code{\obeycr} & @code{\restorecr}

@findex \obeycr
@findex \restorecr
@cindex new line, output as input

The @code{\obeycr} command makes a return in the input file
(@samp{^^M}, internally) the same as @code{\\} (followed by
@code{\relax}).  So each new line in the input will also be a new line
in the output.

@code{\restorecr} restores normal line-breaking behavior.


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

@findex \newline
@cindex new line, starting (paragraph mode)

In ordinary text this is equivalent to double-backslash (@pxref{\\}); it
breaks a line, with no stretching of the text before it.

Inside a @code{tabular} or @code{array} environment, in a column with a
specifier producing a paragraph box, like typically @code{p@{...@}},
@code{\newline} will insert a line break inside of the column, that is,
it does not break the entire row.  To break the entire row use @code{\\}
or its equivalent @code{\tabularnewline}.

This will print @samp{Name:} and @samp{Address:} as two lines in a
single cell of the table.

@example
\begin@{tabular@}@{p@{1in@}@{\hspace@{2in@}@}p@{1in@}@}
  Name: \newline Address: &Date: \\ \hline
\end@{tabular@}
@end example

The @samp{Date:} will be baseline-aligned with @samp{Name:}.


@node \- (hyphenation)
@section @code{\-} (discretionary hyphen)

@findex \- @r{(hyphenation)}
@cindex hyphenation, forcing

The @code{\-} command tells @LaTeX{} that it may hyphenate the word at
that point.  @LaTeX{} is pretty good at hyphenating, and usually finds
most of the correct hyphenation points, while almost never using an
incorrect one.  The @code{\-} command is used for the exceptional
cases.

When you insert @code{\-} commands in a word, the word will only be
hyphenated at those points and not at any of the hyphenation points
that @LaTeX{} might otherwise have chosen.

@node \discretionary
@section @code{\discretionary} (generalized hyphenation point)
@cindex hyphenation, discretionary
@cindex discretionary hyphenation

Synopsis:

@example
\discretionary@{@var{pre-break-text}@}@{@var{post-break-text}@}@{@var{no-break-text}@}
@end example

@c xxx TODO, complete this node, see LaTeX-fr

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

@findex \fussy

The declaration @code{\fussy} (which is the default) makes @TeX{}
picky about line breaking.  This usually avoids too much space between
words, at the cost of an occasional overfull box.

This command cancels the effect of a previous @code{\sloppy} command
(@pxref{\sloppy}).


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

@findex \sloppy

The declaration @code{\sloppy} makes @TeX{} less fussy about line
breaking. This will avoid overfull boxes, at the cost of loose
interword spacing.

Lasts until a @code{\fussy} command is issued (@pxref{\fussy}).


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

@findex \hyphenation
@cindex hyphenation, defining

Synopsis:

@example
\hyphenation@{@var{word-one} @var{word-two}@}
@end example

The @code{\hyphenation} command declares allowed hyphenation points
with a @code{-} character in the given words.  The words are separated
by spaces.  @TeX{} will only hyphenate if the word matches exactly, no
inflections are tried.  Multiple @code{\hyphenation} commands
accumulate.  Some examples (the default @TeX{} hyphenation patterns
misses the hyphenations in these words):

@example
\hyphenation@{ap-pen-dix col-umns data-base data-bases@}
@end example


@node \linebreak & \nolinebreak
@section @code{\linebreak} & @code{\nolinebreak}

@findex \linebreak
@findex \nolinebreak
@cindex line breaks, forcing
@cindex line breaks, preventing

Synopses:

@example
\linebreak[@var{priority}]
\nolinebreak[@var{priority}]
@end example

By default, the @code{\linebreak} (@code{\nolinebreak}) command forces
(prevents) a line break at the current position.  For
@code{\linebreak}, the spaces in the line are stretched out so that it
extends to the right margin as usual.

With the optional argument @var{priority}, you can convert the command
from a demand to a request.  The @var{priority} must be a number from
0 to@tie{}4.  The higher the number, the more insistent the request.


@node Page breaking
@chapter Page breaking

@cindex page breaking
@cindex breaking pages

@LaTeX{} starts new pages asynchronously, when enough material has
accumulated to fill up a page.  Usually this happens automatically,
but sometimes you may want to influence the breaks.

@menu
* \cleardoublepage::           Start a new right-hand page.
* \clearpage::                 Start a new page.
* \newpage::                   Start a new page.
* \enlargethispage::           Enlarge the current page a bit.
* \pagebreak & \nopagebreak::  Forcing & avoiding page breaks.
@end menu


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

@findex \cleardoublepage
@cindex starting on a right-hand page

The @code{\cleardoublepage} command ends the current page and causes all
the pending floating figures and tables that have so far appeared in the
input to be printed.  In a two-sided printing style, it also makes the
next page a right-hand (odd-numbered) page, producing a blank page if
necessary.


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

@findex \clearpage
@cindex flushing floats and starting a page
@cindex starting a new page and clearing floats

The @code{\clearpage} command ends the current page and causes all the
pending floating figures and tables that have so far appeared in the
input to be printed.


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

@findex \newpage
@cindex new page, starting
@cindex starting a new page

The @code{\newpage} command ends the current page, but does not clear
floats (@pxref{\clearpage}).


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

@findex \enlargethispage
@cindex enlarge current page

@code{\enlargethispage@{size@}}

@code{\enlargethispage*@{size@}}

Enlarge the @code{\textheight} for the current page by the specified
amount; e.g., @code{\enlargethispage@{\baselineskip@}} will allow one
additional line.

The starred form tries to squeeze the material together on the page as
much as possible. This is normally used together with an explicit
@code{\pagebreak}.


@node \pagebreak & \nopagebreak
@section @code{\pagebreak} & @code{\nopagebreak}

@findex \pagebreak
@findex \nopagebreak
@cindex page break, forcing
@cindex page break, preventing

Synopses:

@example
\pagebreak[@var{priority}]
\nopagebreak[@var{priority}]
@end example

By default, the @code{\pagebreak} (@code{\nopagebreak}) command forces
(prevents) a page break at the current position.  With
@code{\pagebreak}, the vertical space on the page is stretched out
where possible so that it extends to the normal bottom margin.

With the optional argument @var{priority}, you can convert the
@code{\pagebreak} command from a demand to a request.  The number must
be a number from 0 to@tie{}4.  The higher the number, the more
insistent the request is.


@node Footnotes
@chapter Footnotes

@cindex footnotes, creating

Place a numbered footnote at the bottom of the current page, as here.

@example
No@"{e}l Coward quipped that having to read a footnote is like having
to go downstairs to answer the door, while in the midst of making
love.\footnote@{I wouldn't know, I don't read footnotes.@}
@end example

You can place multiple footnotes on a page. If the text becomes too long
it will flow to the next page.

You can also produce footnotes by combining the @code{\footnotemark} and
the @code{\footnotetext} commands, which is useful in special
circumstances.

To make bibliographic references come out as footnotes you need to
include a bibliographic style with that behavior.

@menu
* \footnote::                Insert a footnote.
* \footnotemark::            Insert footnote mark only.
* \footnotetext::            Insert footnote text only.
* Footnotes in a table::     Table footnotes.  
* Footnotes in section headings::     Chapter or section titles.  
* Footnotes of footnotes::   Multiple classes of footnotes.  
* Multiple reference to footnotes::   Referring to a footnote more than once.  
* Footnote parameters::      Parameters for footnote formatting.
@end menu


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

@findex \footnote

Synopsis:

@example
\footnote[@var{number}]@{@var{text}@}
@end example

Place a numbered footnote @var{text} at the bottom of the current page.

@example
There are over a thousand footnotes in Gibbon's 
\textit@{Decline and Fall of the Roman Empire@}.\footnote@{After
reading an early version with endnotes David Hume complained, 
``One is also plagued with his Notes, according to the present Method 
of printing the Book'' and suggested that they ``only to be printed 
at the Margin or the Bottom of the Page.''@}
@end example

The optional argument @var{number} allows you to specify the footnote
number.  If you use this option then the footnote number counter is not
incremented, and if you do not use it then the counter is incremented.

@cindex footnotes, symbols instead of numbers
@findex \fnsymbol@r{, and footnotes}
@findex \@@fnsymbol
Change how @LaTeX{} shows the footnote counter with something like
@code{\renewcommand@{\thefootnote@}@{\fnsymbol@{footnote@}@}}, which
uses a sequence of symbols (@pxref{\alph \Alph \arabic \roman \Roman
\fnsymbol}).  To make this change global put that in the preamble.  If
you make the change local then you may want to reset the counter with
@code{\setcounter@{footnote@}@{0@}}.  By default @LaTeX{} uses arabic
numbers.

@LaTeX{}'s default puts many restrictions on where you can use a
@code{\footnote}; for instance, you cannot use it in an argument to a
sectioning command such as @code{\chapter} (it can only be used in outer
paragraph mode).  There are some workarounds; see following sections.
@c xx mention packages that fix this

@cindex Footnotes, in a minipage
@cindex mpfootnote counter
In a @code{minipage} environment the @code{\footnote}
command uses the @code{mpfootnote} counter instead of the
@code{footnote} counter, so they are numbered independently.  They are
shown at the bottom of the environment, not at the bottom of the page.
And by default they are shown alphabetically. @xref{minipage}.


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

@findex \footnotemark

Synopsis, one of:

@example
\footnotemark
\footnotemark[@var{number}]
@end example

Put the current footnote number in the
text. (See@tie{}@ref{\footnotetext} for giving the text of the footnote
separately.)  The version with the optional argument @var{number} uses
that number to determine the mark printed. This command can be used in
inner paragraph mode.

This example gives the same institutional affiliation to both the first
and third authors (@code{\thanks} is a version of @code{footnote}).

@example
\title@{A Treatise on the Binomial Theorem@}
\author@{J Moriarty\thanks@{University of Leeds@} 
  \and A C Doyle\thanks@{Durham University@} 
  \and S Holmes\footnotemark[1]@}
\begin@{document@}
\maketitle
@end example 

If you use @code{\footnotemark} without the optional argument then it
increments the footnote counter but if you use the optional @var{number}
then it does not. This produces several consecutive footnote markers
referring to the same footnote.

@example
The first theorem\footnote@{Due to Gauss.@} 
and the second theorem\footnotemark[\value@{footnote@}] 
and the third theorem.\footnotemark[\value@{footnote@}]
@end example


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

@findex \footnotetext

Synopsis, one of:

@example
\footnotetext@{@var{text}@}
\footnotetext[@var{number}]@{@var{text}@}
@end example

Place @var{text} at the bottom of the page as a footnote.  This command
can come anywhere after the @code{\footnotemark} command.  The optional
argument @var{number} changes the displayed footnote number.  The
@code{\footnotetext} command must appear in outer paragraph mode.


@node Footnotes in a table
@section Footnotes in a table

@cindex Footnotes, in a table

Inside a @code{table} environment the @code{\footnote} command does not
work.  For instance, if the code below appears on its own then the
footnote simply disappears; there is a footnote mark in the table cell
but nothing is set at the bottom of the page.

@example
\begin@{center@}
     \begin@{tabular@}@{l|l@}
     \textsc@{Ship@}  &\textsc@{Book@} \\ \hline 
     \textit@{HMS Sophie@}     &Master and Commander  \\ 
     \textit@{HMS Polychrest@} &Post Captain  \\  
     \textit@{HMS Lively@}     &Post Captain \\
     \textit@{HMS Surprise@}   &A number of books\footnote@{Starting with
                                HMS Surprise.@}
     \end@{tabular@}
\end@{center@}
@end example

The solution is to surround the @code{tabular} environment with a
@code{minipage} environment, as here (@pxref{minipage}).

@example
\begin@{center@}
  \begin@{minipage@}@{.5\textwidth@}
    ... tabular material ...
  \end@{minipage@}
\end@{center@}
@end example

The same technique will work inside a floating @code{table} environment
(@pxref{table}).  To get the footnote at the bottom of the page use the
@file{tablefootnote} package, as illustrated in this example.  If you
put @code{\usepackage@{tablefootnote@}} in the preamble and use the code
shown then the footnote appears at the bottom and is numbered in
sequence with other footnotes.

@example
\begin@{table@}
  \centering
     \begin@{tabular@}@{l|l@}
     \textsc@{Date@}  &\textsc@{Campaign@} \\ \hline 
     1862           &Fort Donelson \\ 
     1863           &Vicksburg     \\  
     1865           &Army of Northern Virginia\footnote@{Ending the war.@}
     \end@{tabular@}
    \caption@{Forces captured by US Grant@}
\end@{table@}
@end example


@node Footnotes in section headings
@section Footnotes in section headings

@cindex footnotes, in section headings
@cindex table of contents, avoiding footnotes
Putting a footnote in a section heading, as in:

@example
\section@{Full sets\protect\footnote@{This material due to ...@}@}
@end example

@PkgIndex{footmisc}
@cindex @code{stable} option to @code{footmisc} package
@noindent
causes the footnote to appear at the bottom of the page where the
section starts, as usual, but also at the bottom of the table of
contents, where it is not likely to be desired.  To have it not appear
on the table of contents use the package @file{footmisc} with the
@code{stable} option.

@example
\usepackage[stable]@{footmisc@}
...
\begin@{document@}
...
\section@{Full sets\footnote@{This material due to ...@}@}
@end example

Note that the @code{\protect} is gone; including it would cause the
footnote to reappear on the table of contents.


@node Footnotes of footnotes
@section Footnotes of footnotes

Particularly in the humanities, authors can have multiple classes of
footnotes, including having footnotes of footnotes.  The package
@file{bigfoot} extends @LaTeX{}'s default footnote mechanism in many
ways, including allow these two, as in this example.

@example
\usepackage@{bigfoot@}
\DeclareNewFootnote@{Default@}
\DeclareNewFootnote@{from@}[alph]   % create class \footnotefrom@{@}
 ...
\begin@{document@}
...
The third theorem is a partial converse of the 
second.\footnotefrom@{First noted in Wilson.\footnote@{Second edition only.@}@}
...
@end example


@node Multiple reference to footnotes
@section Multiple references to footnotes

You can refer to a single footnote more than once.  This example
uses the package @file{cleverref}.

@c from SE user Jake http://tex.stackexchange.com/a/10116/339
@example
\usepackage@{cleveref@}[2012/02/15]   % this version of package or later 
\crefformat@{footnote@}@{#2\footnotemark[#1]#3@}
...
\begin@{document@}
...
The theorem is from Evers.\footnote@{\label@{fn:TE@}Tinker and Evers, 1994.@}
The corollary is from Chance.\footnote@{Evers and Chance, 1990.@}
But the key lemma is from Tinker.\cref@{fn:TE@}
...
@end example

This solution will work with the package @file{hyperref}.
See@tie{}@ref{\footnotemark} for a simpler solution in the common case
of multiple authors with the same affiliation.


@node Footnote parameters
@section Footnote parameters

@cindex footnote parameters
@cindex parameters, for footnotes

@ftable @code
@item \footnoterule
Produces the rule separating the main text on a page from the page's
footnotes.  Default dimensions: @code{0.4pt} thick (or wide), and
@code{0.4\columnwidth} long in the standard document classes (except
@code{slides}, where it does not appear).

@item \footnotesep
The height of the strut placed at the beginning of the footnote.  By
default, this is set to the normal strut for @code{\footnotesize}
fonts (@pxref{Font sizes}), therefore there is no extra space between
footnotes.  This is @samp{6.65pt} for @samp{10pt}, @samp{7.7pt} for
@samp{11pt}, and @samp{8.4pt} for @samp{12pt}.

@end ftable


@node Definitions
@chapter Definitions

@cindex definitions

@LaTeX{} has support for making new commands of many different kinds.

@c xx everything in this chapter needs examples.
@c xx Add DeclareRobustCommand (see clsguide.pdf)

@menu
* \newcommand & \renewcommand::           (Re)define a new command.
* \providecommand::                       Define a new command, if name not used.
* \newcounter::                           Define a new counter.
* \newlength::                            Define a new length.
* \newsavebox::                           Define a new box.
* \newenvironment & \renewenvironment::   Define a new environment.
* \newtheorem::                           Define a new theorem-like environment.
* \newfont::                              Define a new font name.
* \protect::                              Using tricky commands.
@end menu


@node \newcommand & \renewcommand
@section @code{\newcommand} & @code{\renewcommand}

@findex \newcommand
@cindex commands, defining new ones
@cindex commands, redefining
@cindex defining a new command
@cindex new commands, defining

@code{\newcommand} and @code{\renewcommand} define and redefine a
command, respectively.  Synopses:

@example
  \newcommand@{\@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
  \newcommand*@{\@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
\renewcommand@{\@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
\renewcommand*@{\@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
@end example

@cindex starred form, defining new commands
@cindex *-form, defining new commands
The starred form of these two commands requires that the arguments not
contain multiple paragraphs of text (not @code{\long}, in plain @TeX{}
terms).

@table @var
@item cmd
Required; @code{\@var{cmd}} is the command name.  For @code{\newcommand}, it
must not be already defined and must not begin with @code{\end}.  For
@code{\renewcommand}, it must already be defined.

@item nargs
Optional; an integer from 0 to 9, specifying the number of arguments
that the command can take, including any optional argument.  If this
argument is not present, the default is for the command to have no
arguments.  When redefining a command, the new version can have a
different number of arguments than the old version.

@item optargdefault
Optional; if this argument is present then the first argument of defined
command @code{\@var{cmd}} is optional, with default value @var{optargdefault}
(which may be the empty string).  If this argument is not present then
@code{\@var{cmd}} does not take an optional argument.

@cindex positional parameter
That is, if @code{\@var{cmd}} is used with square brackets following,
as in @code{\@var{cmd}[@var{myval}]}, then within @var{defn} the first
@dfn{positional parameter} @code{#1} expands @var{myval}.  On the
other hand, if @code{\@var{cmd}} is called without square brackets
following, then within @var{defn} the positional parameter @code{#1}
expands to the default @var{optargdefault}.  In either case, any
required arguments will be referred to starting with @code{#2}.

Omitting @code{[@var{myval}]} in a call is different from having the
square brackets with no contents, as in @code{[]}.  The former results
in @code{#1} expanding to @var{optargdefault}; the latter results in
@code{#1} expanding to the empty string.

@item defn
The text to be substituted for every occurrence of @code{\@var{cmd}}; the
positional parameter @code{#@var{n}} in @var{defn} is replaced by
the text of the @var{n}th argument.

@end table

@TeX{} ignores spaces in the source following an alphabetic control
sequence, as in @samp{\cmd }.  If you actually want a space there, one
solution is to type @code{@{@}} after the command (@samp{\cmd@{@} };
another solution is to use an explicit control space (@samp{\cmd\ }).

A simple example of defining a new command:
@code{\newcommand@{\RS@}@{Robin Smith@}} results in
@code{\RS} being replaced by the longer text.

Redefining an existing command is similar:
@code{\renewcommand@{\qedsymbol@}@{@{\small QED@}@}}.

Here's a command definition with one required argument:

@example
\newcommand@{\defref@}[1]@{Definition~\ref@{#1@}@}
@end example

@noindent Then, @code{\defref@{def:basis@}} expands to
@code{Definition~\ref@{def:basis@}}, which will ultimately expand to
something like @samp{Definition~3.14}.

An example with two required arguments:
@code{\newcommand@{\nbym@}[2]@{$#1 \times #2$@}} is invoked as
@code{\nbym@{2@}@{k@}}.

An example with an optional argument:

@example
\newcommand@{\salutation@}[1][Sir or Madam]@{Dear #1:@}
@end example

@noindent Then, @code{\salutation} gives @samp{Dear Sir or Madam:} while
@code{\salutation[John]} gives @samp{Dear John:}.  And
@code{\salutation[]} gives @samp{Dear :}.

The braces around @var{defn} do not define a group, that is, they do
not delimit the scope of the result of expanding @var{defn}.  So
@code{\newcommand@{\shipname@}[1]@{\it #1@}} is problematic; in this
sentence,

@example
The \shipname@{Monitor@} met the \shipname@{Merrimac@}.
@end example

@noindent the words @samp{met the} would incorrectly be in italics.  Another
pair of braces in the definition is needed, like this:
@code{\newcommand@{\shipname@}[1]@{@{\it #1@}@}}.  Those braces are
part of the definition and thus do define a group.


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

@findex \providecommand
@cindex commands, defining new ones
@cindex defining a new command
@cindex new commands, defining

Defines a command, as long as no command of this name already exists.
Synopses:

@example
\providecommand@{@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
\providecommand*@{@var{cmd}@}[@var{nargs}][@var{optargdefault}]@{@var{defn}@}
@end example

If no command of this name already exists then this has the same effect
as @code{\newcommand} (@pxref{\newcommand & \renewcommand}).  If a
command of this name already exists then this definition does nothing.
This is particularly useful in a style file, or other file that may be
loaded more than once.


@node \newcounter
@section @code{\newcounter}: Allocating a counter

@findex \newcounter
@cindex counters, defining new

Synopsis, one of:

@example
\newcounter@{@var{countername}@}
\newcounter@{@var{countername}@}[@var{supercounter}]
@end example

Globally defines a new counter named @var{countername} and initialize
the new counter to zero.

The name @var{countername} must consists of letters only, and does not
begin with a backslash.  This name must not already be in use by another
counter.

When you use the optional argument @code{[@var{supercounter}]} then
@var{countername} will be numbered within, or subsidiary to, the
existing counter @var{supercounter}.  For example, ordinarily
@code{subsection} is numbered within @code{section} so that any time
@var{supercounter} is incremented with @code{\stepcounter}
(@pxref{\stepcounter}) or @code{\refstepcounter}
(@pxref{\refstepcounter}) then @var{countername} is reset to zero.

@xref{Counters}, for more information about counters.


@node \newlength
@section @code{\newlength}: Allocating a length

@findex \newlength
@cindex lengths, allocating new
@cindex rubber lengths, defining new
@cindex skip register, plain @TeX{}
@cindex glue register, plain @TeX{}

Allocate a new @dfn{length} register.  Synopsis:

@example
\newlength@{\@var{arg}@}
@end example

This command takes one required argument, which must begin with a
backslash (@samp{\}).  It creates a new length register named
@code{\@var{arg}}, which is a place to hold (rubber) lengths such as
@code{1in plus.2in minus.1in} (what plain @TeX{} calls a @code{skip}
register).  The register gets an initial value of zero.  The control
sequence @code{\@var{arg}} must not already be defined.

@xref{Lengths}, for more about lengths.


@node \newsavebox
@section @code{\newsavebox}: Allocating a box

@findex \newsavebox
@cindex box, allocating new

Allocate a ``bin'' for holding a box.  Synopsis:

@example
\newsavebox@{\@var{cmd}@}
@end example

Defines @code{\@var{cmd}} to refer to a new bin for storing boxes.
Such a box is for holding typeset material, to use multiple times
(@pxref{Boxes}) or to measure or manipulate.  The name
@code{\@var{cmd}} must start with a backslash (@samp{\}), and must not
be already defined.

The allocation of a box is global.  This command is fragile
(@pxref{\protect}).


@node \newenvironment & \renewenvironment
@section @code{\newenvironment} & @code{\renewenvironment}

@findex \newenvironment
@findex \renewenvironment
@cindex environments, defining
@cindex defining new environments
@cindex redefining environments

These commands define or redefine an environment @var{env}, that is,
@code{\begin@{@var{env}@} @var{body} \end@{@var{env}@}}.  Synopses:

@example
   \newenvironment@{@var{env}@}[@var{nargs}][@var{optargdefault}]@{@var{begdefn}@}@{@var{enddefn}@}
  \newenvironment*@{@var{env}@}[@var{nargs}][@var{optargdefault}]@{@var{begdefn}@}@{@var{enddefn}@}
 \renewenvironment@{@var{env}@}[@var{nargs}][@var{optargdefault}]@{@var{begdefn}@}@{@var{enddefn}@}
\renewenvironment*@{@var{env}@}[@var{nargs}][@var{optargdefault}]@{@var{begdefn}@}@{@var{enddefn}@}
@end example

@cindex @code{*}-form of environment commands 	 
The starred form of these commands requires that the arguments not
contain multiple paragraphs of text.  The body of these environments can
still contain multiple paragraphs.

@table @var
@item env
Required; the environment name.  It consists only of letters or the
@code{*} character, and thus does not begin with backslash
(@code{\}).  It must not begin with the string @code{end}.  For
@code{\newenvironment}, the name @var{env} must not be the name of an
already existing environment, and also the command @code{\@var{env}}
must be undefined.  For @code{\renewenvironment}, @var{env} must be the
name of an existing environment.

@item nargs
Optional; an integer from 0 to 9 denoting the number of arguments of
that the environment will take.  When the environment is used these
arguments appear after the @code{\begin}, as in
@code{\begin@{@var{env}@}@{@var{arg1}@}@dots{}@{@var{argn}@}}.  If this
argument is not present then the default is for the environment to have
no arguments.  When redefining an environment, the new version can have
a different number of arguments than the old version.

@item optargdefault
Optional; if this argument is present then the first argument of the
defined environment is optional, with default value @var{optargdefault}
(which may be the empty string).  If this argument is not present then
the environment does not take an optional argument.

That is, when @code{[@var{optargdefault}]} is present in the
environment definition, if @code{\begin@{@var{env}@}} is used with
square brackets following, as in
@code{\begin@{@var{env}@}[@var{myval}]}, then, within @var{begdefn},
the positional parameter @code{#1} expands to @var{myval}.  If
@code{\begin@{@var{env}@}} is called without square brackets
following, then, within within @var{begdefn}, the positional parameter
@code{#1} expands to the default @var{optargdefault}.  In either case,
any required arguments will be referred to starting with @code{#2}.

Omitting @code{[@var{myval}]} in the call is different from having the
square brackets with no contents, as in @code{[]}.  The former results
in @code{#1} expanding to @var{optargdefault}; the latter results in
@code{#1} expanding to the empty string.

@item begdefn
Required; the text expanded at every occurrence of
@code{\begin@{@var{env}@}}.  Within @var{begdef}, the @var{n}th
positional parameter (i.e., @code{#@var{n}}) is replaced by the text
of the @var{n}th argument.

@item enddefn
Required; the text expanded at every occurrence of
@code{\end@{@var{env}@}}.  This may not contain any positional
parameters, so @code{#@var{n}} cannot be used here (but see the final
example below).

@end table

All environments, that is to say the @var{begdefn} code, the environment
body and the @var{enddefn} code, are processed within a group.  Thus, in
the first example below, the effect of the @code{\small} is limited to
the quote and does not extend to material following the environment.

This example gives an environment like @LaTeX{}'s @code{quotation}
except that it will be set in smaller type:

@example
\newenvironment@{smallquote@}@{%
  \small\begin@{quotation@}
@}@{%
  \end@{quotation@}
@}
@end example

This one shows the use of arguments; it gives a quotation environment
that cites the author:

@example
\newenvironment@{citequote@}[1][Shakespeare]@{%
  \begin@{quotation@}
  \noindent\textit@{#1@}: 
@}@{%
  \end@{quotation@}
@}
@end example

@noindent The author's name is optional, and defaults to @samp{Shakespeare}.
In the document, use the environment like this:

@example
\begin@{citequote@}[Lincoln]
  ...
\end@{citequote@}
@end example

The final example shows how to save the value of an argument to use in 
@var{enddefn}, in this case in a box (@pxref{\sbox}):

@example
\newsavebox@{\quoteauthor@}
\newenvironment@{citequote@}[1][Shakespeare]@{%
  \sbox\quoteauthor@{#1@}%
  \begin@{quotation@} 
@}@{%
  \hspace@{1em plus 1fill@}---\usebox@{\quoteauthor@}
  \end@{quotation@}
@}
@end example


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

@findex \newtheorem
@cindex theorems, defining
@cindex defining new theorems

@cindex theorem-like environment
@cindex environment, theorem-like
Define a new theorem-like environment.  Synopses:

@example
\newtheorem@{@var{name}@}@{@var{title}@}
\newtheorem@{@var{name}@}@{@var{title}@}[@var{numbered_within}]
\newtheorem@{@var{name}@}[@var{numbered_like}]@{@var{title}@}
@end example

Using the first form, @code{\newtheorem@{@var{name}@}@{@var{title}@}}
creates an environment that will be labelled with @var{title}.  See the
first example below.

The second form
@code{\newtheorem@{@var{name}@}@{@var{title}@}[@var{numbered_within}]}
creates an environment whose counter is subordinate to the existing
counter @var{numbered_within} (its counter will be reset when
@var{numbered_within} is reset).


The third form
@code{\newtheorem@{@var{name}@}[@var{numbered_like}]@{@var{title}@}},
with optional argument between the two required arguments, will create
an environment whose counter will share the previously defined counter
@var{numbered_like}.

You can specify one of @var{numbered_within} and @var{numbered_like},
or neither, but not both.

This command creates a counter named @var{name}.  In addition, unless
the optional argument @var{numbered_like} is used, inside of the
theorem-like environment the current @code{\ref} value will be that of
@code{\the@var{numbered_within}} (@pxref{\ref}).

This declaration is global.  It is fragile (@pxref{\protect}).

Arguments:

@table @var
@item name
The name of the environment.  It must not begin with a backslash
(@samp{\}).  It must not be the name of an existing environment; indeed,
the command name @code{\@var{name}} must not already be defined as anything.

@item title
The text printed at the beginning of the environment, before the
number. For example, @samp{Theorem}.

@item numbered_within
Optional; the name of an already defined counter, usually a sectional
unit such as @code{chapter} or @code{section}.  When the
@var{numbered_within} counter is reset then the @var{name} environment's
counter will also be reset.

If this optional argument is not used then the command
@code{\the@var{name}} is set to @code{\arabic@{@var{name}@}}.

@item numbered_like
Optional; the name of an already defined theorem-like environment. The
new environment will be numbered in sequence with @var{numbered_like}.

@end table

Without any optional arguments the environments are numbered
sequentially.  The example below has a declaration in the preamble that
results in @samp{Definition@tie{}1} and @samp{Definition@tie{}2} in the
output.

@example
\newtheorem@{defn@}@{Definition@}
\begin@{document@}
\section@{...@}
\begin@{defn@}
  First def 
\end@{defn@}

\section@{...@}
\begin@{defn@}
  Second def
\end@{defn@}
@end example

Because the next example specifies the optional argument
@var{numbered_within} to @code{\newtheorem} as @code{section}, the
example, with the same document body, gives @samp{Definition@tie{}1.1}
and @samp{Definition@tie{}2.1}.

@example
\newtheorem@{defn@}@{Definition@}[section]
\begin@{document@}
\section@{...@}
\begin@{defn@}
  First def 
\end@{defn@}

\section@{...@}
\begin@{defn@}
  Second def
\end@{defn@}
@end example

In the next example there are two declarations in the preamble, the
second of which calls for the new @code{thm} environment to use the same
counter as @code{defn}.  It gives @samp{Definition@tie{}1.1}, followed
by @samp{Theorem@tie{}2.1} and @samp{Definition@tie{}2.2}.

@example
\newtheorem@{defn@}@{Definition@}[section]
\newtheorem@{thm@}[defn]@{Theorem@}
\begin@{document@}
\section@{...@}
\begin@{defn@}
  First def 
\end@{defn@}

\section@{...@}
\begin@{thm@}
  First thm
\end@{thm@}

\begin@{defn@}
  Second def
\end@{defn@}
@end example


@node \newfont
@section @code{\newfont}: Define a new font (obsolete)

@findex \newfont
@cindex fonts, new commands for
@cindex defining new fonts

@code{\newfont}, now obsolete, defines a command that will switch fonts.
Synopsis:

@example
\newfont@{\@var{cmd}@}@{@var{font description}@}
@end example

This defines a control sequence @code{\@var{cmd}} that will change the
current font.  @LaTeX{} will look on your system for a file named
@file{@var{fontname}.tfm}.  The control sequence must must not already
be defined.  It must begin with a backslash (@samp{\}).

@findex .fd @r{file}
This command is obsolete.  It is a low-level command for setting up an
individual font.  Today fonts are almost always defined in families
(which allows you to, for example, associate a boldface with a roman)
through the so-called ``New Font Selection Scheme'', either by using
@file{.fd} files or through the use of an engine that can access
system fonts such as Xe@LaTeX{} (@pxref{@TeX{} engines}).
@c xx explain nfss somewhere

@cindex at clause, in font definitions
@cindex design size, in font definitions
But since it is part of @LaTeX{}, here is an explanation: the
@var{font description} consists of a @var{fontname} and an optional
@dfn{at clause}; this can have the form either @code{at @var{dimen}}
or @code{scaled @var{factor}}, where a @var{factor} of @samp{1000}
means no scaling.  For @LaTeX{}'s purposes, all this does is scale all
the character and other font dimensions relative to the font's design
size, which is a value defined in the @file{.tfm} file.

This example defines two equivalent fonts and typesets a few
characters in each:

@example
\newfont@{\testfontat@}@{cmb10 at 11pt@}
\newfont@{\testfontscaled@}@{cmb10 scaled 1100@}
\testfontat abc
\testfontscaled abc
@end example


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

@findex \protect
@cindex fragile commands
@cindex robust commands

All @LaTeX{} commands are either @dfn{fragile} or @dfn{robust}.  A
fragile command can break when it is used in the argument to certain
other commands.  Commands that contain data that @LaTeX{} writes to an
auxiliary file and re-reads later are fragile.  This includes material
that goes into a table of contents, list of figures, list of tables,
etc.  Fragile commands also include line breaks, any command that has an
optional argument, and many more. To prevent such commands from
breaking, one solution is to preceded them with the command
@code{\protect}.

For example, when @LaTeX{} runs the @code{\section@{@var{section
name}@}} command it writes the @var{section name} text to the
@file{.aux} auxiliary file, moving it there for use elsewhere in the
document such as in the table of contents.  Any argument that is
internally expanded by @LaTeX{} without typesetting it directly is
referred to as a 
@cindex moving arguments
@dfn{moving argument}.  A command is fragile if it can
expand during this process into invalid @TeX{} code.  Some examples of
moving arguments are those that appear in the @code{\caption@{...@}}
command (@pxref{figure}), in the @code{\thanks@{...@}} command
(@pxref{\maketitle}), and in @@-expressions in the @code{tabular} and
@code{array} environments (@pxref{tabular}).

If you get strange errors from commands used in moving arguments, try
preceding it with @code{\protect}.  Every fragile commands must be
protected with their own @code{\protect}.  

Although usually a @code{\protect} command doesn't hurt, length
commands are robust and should not be preceded by a @code{\protect}
command. Nor can a @code{\protect} command be used in the argument to
@code{\addtocounter} or @code{\setcounter} command.

In this example the @code{\caption} command gives a mysterious error
about an extra curly brace.  Fix the problem by preceding each
@code{\raisebox} command with @code{\protect}.

@example
\begin@{figure@}
  ...
  \caption@{Company headquarters of A\raisebox@{1pt@}@{B@}\raisebox@{-1pt@}@{C@}@}
\end@{figure@}
@end example

In the next example the @code{\tableofcontents} command gives an error
because the @code{\(..\)} in the section title expands to illegal @TeX{}
in the @file{.toc} file.  You can solve this by changing @code{\(..\)}
to @code{\protect\(..\protect\)}.

@example
\begin@{document@}
\tableofcontents
...
\section@{Einstein's \( e=mc^2 \)@}
...
@end example


@node Counters
@chapter Counters

@cindex counters, a list of
@cindex variables, a list of

Everything @LaTeX{} numbers for you has a counter associated with
it. The name of the counter is often the same as the name of the
environment or command associated with the number, except that the
counter's name has no backslash@tie{}@code{\}.  Thus, associated with
the @code{\chapter} command is the @code{chapter} counter that keeps
track of the chapter number.  

Below is a list of the counters used in @LaTeX{}'s standard document
classes to control numbering.

@example
part            paragraph       figure          enumi
chapter         subparagraph    table           enumii
section         page            footnote        enumiii
subsection      equation        mpfootnote      enumiv
subsubsection
@end example

The @code{mpfootnote} counter is used by the @code{\footnote} command
inside of a minipage (@pxref{minipage}).  The counters @code{enumi}
through @code{enumiv} are used in the @code{enumerate} environment, for
up to four levels of nesting (@pxref{enumerate}).

New counters are created with @code{\newcounter}.  @xref{\newcounter}.


@menu
* \alph \Alph \arabic \roman \Roman \fnsymbol:: Print value of a counter.
* \usecounter::       Use a specified counter in a list environment.
* \value::            Use the value of a counter in an expression.  
* \setcounter::       Set the value of a counter.
* \addtocounter::     Add a quantity to a counter.
* \refstepcounter::   Add to a counter.
* \stepcounter::      Add to a counter, resetting subsidiary counters.
* \day \month \year:: Numeric date values.
@end menu


@node \alph \Alph \arabic \roman \Roman \fnsymbol
@section @code{\alph \Alph \arabic \roman \Roman \fnsymbol}: Printing counters

@cindex counters, printing

Print the value of a counter, in a specified style.  For instance, if
the counter @var{counter} has the value 1 then a
@code{\alph@{@var{counter}@}} in your source will result in a lower case
letter@tie{}a appearing in the output.

All of these commands take a single counter as an argument, for
instance, @code{\alph@{enumi@}}.  Note that the counter name does not
start with a backslash.

@ftable @code
@item \alph@{@var{counter}@}
Print the value of @var{counter} in lowercase letters: `a', `b', @enddots{}

@item \Alph@{@var{counter}@}
Print in uppercase letters: `A', `B', @enddots{}

@item \arabic@{@var{counter}@}
Print in Arabic numbers: `1', `2', @enddots{}

@item \roman@{@var{counter}@}
Print in lowercase roman numerals: `i', `ii', @enddots{}

@item \Roman@{@var{counter}@}
Print in uppercase roman numerals: `I', `II', @enddots{}

@item \fnsymbol@{@var{counter}@}
Prints the value of @var{counter} in a specific sequence of nine
symbols (conventionally used for labeling footnotes).  The value of
@var{counter} must be between@tie{}1 and@tie{}9, inclusive.

Here are the symbols:

@multitable  @columnfractions .33 .33 .33
@headitem Name@tab Command@tab@iftexthenelse{Symbol,Equivalent Unicode symbol and/or numeric code point}
@item
asterisk@tab@code{\ast}@tab@iftexthenelse{@math{@ast},*}
@item
dagger@tab@code{\dagger}@tab@BES{2020,\dagger}
@item
ddagger@tab@code{\ddagger}@tab@BES{2021,\ddagger}
@item
section-sign@tab@code{\S}@tab@BES{00A7,\S}
@item
paragraph-sign@tab@code{\P}@tab@BES{00B6,\P}
@item
double-vert@tab@code{\parallel}@tab@BES{2016,\parallel}
@item
double-asterisk@tab@code{\ast\ast}@tab@iftexthenelse{@math{@ast@ast},**}
@item
double-dagger@tab@code{\dagger\dagger}@tab@BES{2020,\dagger}@BES{2020,\dagger}
@item
double-ddagger@tab@code{\ddagger\ddagger}@tab@BES{2021,\ddagger}@BES{2021,\ddagger}
@end multitable

@end ftable


@node \usecounter
@section @code{\usecounter@{@var{counter}@}}

@findex \usecounter
@cindex list items, specifying counter
@cindex numbered items, specifying counter

Synopsis:

@example
\usecounter@{@var{counter}@}
@end example

In the @code{list} environment, when used in the second argument, this
command sets up @var{counter} to number the list items.  It initializes
@var{counter} to zero, and arranges that when @code{\item} is called
without its optional argument then @var{counter} is incremented by
@code{\refstepcounter}, making its value be the current @code{ref}
value.  This command is fragile (@pxref{\protect}).

Put in the preamble, this makes a new list environment enumerated with
@var{testcounter}:

@example
\newcounter@{testcounter@}
\newenvironment@{test@}@{%
  \begin@{list@}@{@}@{%
    \usecounter@{testcounter@}
  @}
@}@{%
  \end@{list@}
@}
@end example


@node \value
@section @code{\value@{@var{counter}@}}

@findex \value
@cindex counters, getting value of

Synopsis:

@example
\value@{@var{counter}@}
@end example

This command expands to the value of @var{counter}.  It is often used
in @code{\setcounter} or @code{\addtocounter}, but @code{\value} can
be used anywhere that @LaTeX{} expects a number.  It must not be
preceded by @code{\protect} (@pxref{\protect}).

The @code{\value} command is not used for typesetting the value of the
counter.  @xref{\alph \Alph \arabic \roman \Roman \fnsymbol}.

This example outputs @samp{Test counter is@tie{}6. Other counter
is@tie{}5.}.

@example
\newcounter@{test@} \setcounter@{test@}@{5@}
\newcounter@{other@} \setcounter@{other@}@{\value@{test@}@}
\addtocounter@{test@}@{1@}

Test counter is \arabic@{test@}.
Other counter is \arabic@{other@}.
@end example

This example inserts @code{\hspace@{4\parindent@}}.

@example
\setcounter@{myctr@}@{3@} \addtocounter@{myctr@}@{1@}
\hspace@{\value@{myctr@}\parindent@}
@end example


@node \setcounter
@section @code{\setcounter@{@var{counter}@}@{@var{value}@}}

@findex \setcounter
@cindex counters, setting
@cindex setting counters

Synopsis:

@example
\setcounter@{@var{counter}@}@{@var{value}@}
@end example

The @code{\setcounter} command globally sets the value of @var{counter}
to the @var{value} argument.  Note that the counter name does not start
with a backslash.

In this example the section value appears as @samp{V}.

@example
\setcounter@{section@}@{5@}
Here it is in Roman: \Roman@{section@}.
@end example


@node \addtocounter
@section @code{\addtocounter@{@var{counter}@}@{@var{value}@}}

@findex \addtocounter

The @code{\addtocounter} command globally increments @var{counter} by
the amount specified by the @var{value} argument, which may be negative.

In this example the section value appears as @samp{VII}.

@example
\setcounter@{section@}@{5@}
\addtocounter@{section@}@{2@}
Here it is in Roman: \Roman@{section@}.
@end example


@node \refstepcounter
@section @code{\refstepcounter@{@var{counter}@}}

@findex \refstepcounter

The @code{\refstepcounter} command works in the same way as
@code{\stepcounter} (@pxref{\stepcounter}): it globally increments the
value of @var{counter} by one and resets the value of any counter
numbered within it.  (For the definition of ``counters numbered
within'', @pxref{\newcounter}.)

In addition, this command also defines the current @code{\ref} value
to be the result of @code{\thecounter}.

While the counter value is set globally, the @code{\ref} value is set
locally, i.e., inside the current group.


@node \stepcounter
@section @code{\stepcounter@{@var{counter}@}}

@findex \stepcounter

The @code{\stepcounter} command globally adds one to @var{counter} and
resets all counters numbered within it.  (For the definition of
``counters numbered within'', @pxref{\newcounter}.)


@node \day \month \year
@section @code{\day \month \year}: Predefined counters

@findex \day
@findex \month
@findex \year

@LaTeX{} defines counters for the day of the month (@code{\day},
1--31), month of the year (@code{\month}, 1--12), and year
(@code{\year}, Common Era).  When @TeX{} starts up, they are
set to the current values on the system where @TeX{} is running.  They
are not updated as the job progresses.

The related command @code{\today} produces a string representing the
current day (@pxref{\today}).


@node Lengths
@chapter Lengths

@cindex lengths, defining and using

A @dfn{length} is a measure of distance.  Many @LaTeX{} commands take a
length as an argument.

Lengths come in two types.  A @dfn{rigid length} (what Plain @TeX{}
calls a @dfn{dimen}) such as @code{10pt} cannot contain a @code{plus} or
@code{minus} component.  A @dfn{rubber length} (what Plain @TeX{} calls
a @dfn{skip}) can contain those, as with @code{1cm plus0.05cm
minus0.01cm}.  These give the ability to stretch or shrink; the length
in the prior sentence could appear in the output as long as 1.05@tie{}cm
or as short as 0.99@tie{}cm, depending on what @TeX{}'s typesetting
algorithm finds optimum.

The @code{plus} or @code{minus} component of a rubber length can contain
a @dfn{fill} component, as in @code{1in plus2fill}.  This gives the
length infinite stretchability or shrinkability, so that the length in
the prior sentence can be set by @TeX{} to any distance greater than or
equal to 1@tie{}inch.  @TeX{} actually provides three infinite glue
components @code{fil}, @code{fill}, and @code{filll}, such that the
later ones overcome the earlier ones, but only the middle value is
ordinarily used.  @xref{\hfill}, @xref{\vfill}.

Multiplying an entire rubber length by a number turns it into a rigid
length, so that after @code{\setlength@{\ylength@}@{1in plus 0.2in@}}
and @code{\setlength@{\zlength@}@{3\ylength@}} then the value of
@code{\zlength} is @code{3in}.


@menu
* Units of length::     The units that @LaTeX{} knows.
* \setlength::          Set the value of a length.
* \addtolength::        Add a quantity to a length.
* \settodepth::         Set a length to the depth of something.
* \settoheight::        Set a length to the height of something.
* \settowidth::         Set a length to the width of something.
* Predefined lengths::  Lengths that are, like, predefined.
@end menu


@node Units of length
@section Units of length

@cindex units, of length

@TeX{} and @LaTeX{} know about these units both inside and outside of
math mode.

@table @code
@item pt 
@findex pt
@cindex Point
Point 1/72.27 inch.  The conversion to metric units, to two decimal
places, is 1@dmn{point} = 2.85@dmn{mm} = 28.45@dmn{cm}. 

@item pc
@cindex pica
@findex pc
Pica, 12 pt

@item in 
@findex in
@findex inch
Inch,  72.27 pt

@item  bp 
@findex bp
@cindex Big point
Big point, 1/72 inch.  This length is the definition of a point in
PostScript and many desktop publishing systems.

@item cm 
@cindex Centimeter
@findex cm
Centimeter

@item mm 
@cindex Millimeter
@findex mm
Millimeter

@item dd 
@cindex Didot point
@findex dd
Didot point, 1.07 pt

@item cc 
@cindex Cicero
@findex cc
Cicero, 12 dd

@item sp 
@cindex Scaled point
@findex sp
Scaled point, 1/65536 pt

@end table 

@cindex ex
@cindex x-height
@findex ex
@cindex m-width
@cindex em
@findex em
Two other lengths that are often used are values set by the designer of
the font.  The x-height of the current font @dfn{ex}, traditionally the
height of the lower case letter x, is often used for vertical
lengths. Similarly @dfn{em}, traditionally the width of the capital
letter M, is often used for horizontal lengths (there is also
@code{\enspace}, which is @code{0.5em}).  Use of these can help make a
definition work better across font changes.  For example, a definition
of the vertical space between list items given as
@code{\setlength@{\itemsep@}@{1ex plus 0.05ex minus 0.01ex@}} is more
likely to still be reasonable if the font is changed than a definition
given in points.

@cindex mu, math unit
@findex mu
In math mode, many definitions are expressed in terms of the math unit
@dfn{mu} given by 1 em = 18 mu, where the em is taken from the current
math symbols family.  @xref{Spacing in math mode}.


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

@findex \setlength
@cindex lengths, setting

Synopsis:

@example
\setlength@{@var{\len}@}@{@var{amount}@}
@end example

The @code{\setlength} sets the value of @dfn{length command}
@cindex length command
@code{\@var{len}} to the @var{value} argument which can be expressed in any
units that @LaTeX{} understands, i.e., inches (@code{in}), millimeters
(@code{mm}), points (@code{pt}), big points (@code{bp}), etc.


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

@findex \addtolength
@cindex lengths, adding to

Synopsis:

@example
\addtolength@{@var{\len}@}@{@var{amount}@}
@end example


The @code{\addtolength} command increments a length command @code{\@var{len}}
by the amount specified in the @var{amount} argument, which may be
negative.


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

@findex \settodepth

Synopsis:

@example
\settodepth@{\@var{len}@}@{@var{text}@}
@end example

The @code{\settodepth} command sets the value of a length command
@code{\@var{len}} equal to the depth of the @var{text} argument.


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

@findex \settoheight

Synopsis:

@example
\settoheight@{\@var{len}@}@{text@}
@end example

The @code{\settoheight} command sets the value of a length command @code{\@var{len}}
equal to the height of the @code{text} argument.



@node \settowidth
@section @code{\settowidth@{\@var{len}@}@{@var{text}@}}

@findex \settowidth

Synopsis:

@example
\settowidth@{\@var{len}@}@{@var{text}@}
@end example

The @code{\settowidth} command sets the value of the command @var{\len}
to the width of the @var{text} argument.


@node Predefined lengths
@section Predefined lengths

@cindex lengths, predefined
@cindex predefined lengths

@code{\width}
@findex \width

@code{\height}
@findex \height

@code{\depth}
@findex \depth

@code{\totalheight}
@findex \totalheight

These length parameters can be used in the arguments of the box-making
commands (@pxref{Boxes}).  They specify the natural width, etc., of
the text in the box. @code{\totalheight} equals @math{@code{@backslashchar{}height} +
@code{@backslashchar{}depth}}. To make a box with the text stretched to double the
natural size, e.g., say

@example
\makebox[2\width]@{Get a stretcher@}
@end example


@node Making paragraphs
@chapter Making paragraphs

@cindex making paragraphs
@cindex paragraphs

A paragraph is ended by one or more completely blank lines---lines not
containing even a @code{%}.  A blank line should not appear where a new
paragraph cannot be started, such as in math mode or in the argument of
a sectioning command.

@menu
* \indent::        Indent this paragraph.
* \noindent::      Do not indent this paragraph.
* \parskip::       Space added before paragraphs.
* Marginal notes:: Putting remarks in the margin.
@end menu


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

@findex \indent
@findex \parindent
@cindex indent, forcing

@code{\indent} produces a horizontal space whose width equals to the
@code{\parindent} length, the normal paragraph indentation.  It is used
to add paragraph indentation where it would otherwise be suppressed.

The default value for @code{\parindent} is @code{1em} in two-column
mode, otherwise @code{15pt} for @code{10pt} documents, @code{17pt} for
@code{11pt}, and @code{1.5em} for @code{12pt}.


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

@findex \noindent
@cindex indent, suppressing

When used at the beginning of the paragraph, this command suppresses any
paragraph indentation, as in this example.

@example
... end of the prior paragraph.

\noindent This paragraph is not indented.
@end example

It has no effect when used in the middle of a paragraph.

To eliminate paragraph indentation in an entire document, put
@code{\setlength@{\parindent@}@{0pt@}} in the preamble.


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

@findex \parskip
@cindex vertical space before paragraphs

@code{\parskip} is a rubber length defining extra vertical space added
before each paragraph.  The default is @code{0pt plus1pt}.


@node Marginal notes
@section Marginal notes

@cindex marginal notes
@cindex notes in the margin
@cindex remarks in the margin
@findex \marginpar

Synopsis:

@example
\marginpar[@var{left}]@{@var{right}@}
@end example

The @code{\marginpar} command creates a note in the margin.  The first
line of the note will have the same baseline as the line in the text
where the @code{\marginpar} occurs.

When you only specify the mandatory argument @var{right}, the text
will be placed

@itemize @bullet
@item
in the right margin for one-sided layout (option @code{oneside}, see @ref{Document class options});
@item
in the outside margin for two-sided layout (option @code{twoside}, see @ref{Document class options});
@item
in the nearest margin for two-column layout (option @code{twocolumn}, see @ref{Document class options}).
@end itemize

@findex \reversemarginpar
@findex \normalmarginpar
The command @code{\reversemarginpar} places subsequent marginal notes
in the opposite (inside) margin.  @code{\normalmarginpar} places them
in the default position.

When you specify both arguments, @var{left} is used for the left
margin, and @var{right} is used for the right margin.

The first word will normally not be hyphenated; you can enable
hyphenation there by beginning the node with @code{\hspace@{0pt@}}.

These parameters affect the formatting of the note:

@ftable @code
@item \marginparpush
Minimum vertical space between notes; default @samp{7pt} for
@samp{12pt} documents, @samp{5pt} else.

@item \marginparsep
Horizontal space between the main text and the note; default
@samp{11pt} for @samp{10pt} documents, @samp{10pt} else.

@item \marginparwidth
Width of the note itself; default for a one-sided @samp{10pt} document
is @samp{90pt}, @samp{83pt} for @samp{11pt}, and @samp{68pt} for
@samp{12pt}; @samp{17pt} more in each case for a two-sided document.
In two column mode, the default is @samp{48pt}.

@end ftable

The standard @LaTeX{} routine for marginal notes does not prevent
notes from falling off the bottom of the page.
@c  @TeX{} FAQ entry on this topic (xx when there):
@c @url{http://www.tex.ac.uk/cgi-bin/texfaq2html?label=marginparside}.
@c (+marginfix)


@node Math formulas
@chapter Math formulas

@cindex math formulas
@cindex formulas, math
@cindex math mode, entering
@EnvIndex{math}
@EnvIndex{displaymath}
@EnvIndex{equation}

There are three environments that put @LaTeX{} in math mode:

@table @code
@item math
For formulas that appear right in the text.
@item displaymath
For formulas that appear on their own line.
@item equation
The same as the displaymath environment except that it adds an equation
number in the right margin.
@end table

@findex \(
@findex \)
@findex \[
@findex \]
The @code{math} environment can be used in both paragraph and LR mode,
but the @code{displaymath} and @code{equation} environments can be used
only in paragraph mode.  The @code{math} and @code{displaymath}
environments are used so often that they have the following short forms:

@example
\(...\)   @r{instead of}   \begin@{math@}...\end@{math@}
\[...\]   @r{instead of}   \begin@{displaymath@}...\end@{displaymath@}
@end example

@findex $
In fact, the @code{math} environment is so common that it has an even
shorter form:

@example
$ ... $   @r{instead of}   \(...\)
@end example

@findex \boldmath
@findex \unboldmath
The @code{\boldmath} command changes math letters and symbols to be in
a bold font.  It is used @emph{outside} of math mode.  Conversely, the
@code{\unboldmath} command changes math glyphs to be in a normal font;
it too is used @emph{outside} of math mode.

@c xx own section? Math fonts?
@findex \displaystyle
The @code{\displaystyle} declaration forces the size and style of the
formula to be that of @code{displaymath}, e.g., with limits above and
below summations.  For example:

@example
$\displaystyle \sum_@{n=0@}^\infty x_n $
@end example

@c xx see also \cal, \mathcal

@menu
* Subscripts & superscripts::   Also known as exponent or index.
* Math symbols::                Various mathematical squiggles.
* Math functions::              Math function names like sin and exp.
* Math accents::                Accents in math.
* Spacing in math mode::        Thick, medium, thin and negative spaces.
* Math miscellany::             Stuff that doesn't fit anywhere else.
@end menu


@node Subscripts & superscripts
@section Subscripts & superscripts

@cindex superscript
@cindex subscript
@cindex exponent
@findex _
@findex ^

In math mode, use the caret character@tie{}@code{^} to make the
@var{exp} appear as a superscript: @code{^@{@var{exp}@}}.
Similarly, in math mode, underscore@tie{}@code{_@{@var{exp}@}} makes a
subscript out of @var{exp}.

In this example the @code{0} and @code{1} appear as subscripts while the
@code{2} is a superscript.

@example
\( (x_0+x_1)^2 \)
@end example 

To have more than one character in @var{exp} use curly braces as in
@code{e^@{-2x@}}.

@LaTeX{} handles superscripts on superscripts, and all of that stuff, in
the natural way, so expressions such as @code{e^@{x^2@}} and
@code{x_@{a_0@}} will look right.  It also does the right thing when
something has both a subscript and a superscript.  In this example the
@code{0} appears at the bottom of the integral sign while the @code{10}
appears at the top.
 
@example
\int_0^@{10@} x^2 \,dx
@end example

You can put a superscript or subscript before a symbol with a construct
such as @code{@{@}_t K^2} in math mode (the initial @code{@{@}} prevents
the prefixed subscript from being attached to any prior symbols in the
expression).

Outside of math mode, a construct like @code{A
test$_\textnormal@{subscript@}$} will produce a subscript typeset in
text mode, not math mode.  Note that there are packages specialized for
writing Chemical formulas such as @file{mhchem}.
@c xx display mode


@node Math symbols
@section Math symbols

@cindex math symbols
@cindex symbols, math
@cindex greek letters

@LaTeX{} provides almost any mathematical symbol you're likely to need.
For example, if you include @code{$\pi$} in your source, you will get
the pi symbol @BES{03C0,\pi}.
 
Below is a list of commonly-available symbols.  It is by no means an
exhaustive list.  Each symbol here is described with a short phrase, and
its symbol class (which determines the spacing around it) is given in
parenthesis.  Unless said otherwise, the commands for these symbols can
be used only in math mode.

To redefine a command so that it can be used whatever the current mode,
see @ref{\ensuremath}.


@c xx Add Negation: @code{} for negations of relevant symbols
@c Useful: http://www.w3.org/TR/WD-math-970515/section6.html

@ftable @code
@item \|
@BES{2225,\|} Parallel (relation). Synonym:@tie{}@code{\parallel}.

@item \aleph
@BES{2135,\aleph} Aleph, transfinite cardinal (ordinary).

@item \alpha
@BES{03B1,\alpha} Lower case Greek letter alpha (ordinary).

@item \amalg
@BES{2A3F,\amalg} Disjoint union (binary)

@item \angle
@BES{2220,\angle} Geometric angle (ordinary). Similar: less-than
sign@tie{}@code{<} and angle bracket@tie{}@code{\langle}.

@item \approx
@BES{2248,\approx} Almost equal to (relation).

@item \ast
@BES{2217,\ast} Asterisk operator, convolution, six-pointed
(binary). Synonym:@tie{}@code{*}, which is often a superscript or
subscript, as in the Kleene star. Similar:@tie{}@code{\star}, which is
five-pointed, and is sometimes used as a general binary operation, and
sometimes reserved for cross-correlation.

@item \asymp
@BES{224D,\asymp} Asymptotically equivalent (relation).

@item \backslash
\ Backslash (ordinary).  Similar: set minus@tie{}@code{\setminus}, and
@code{\textbackslash} for backslash outside of math mode.

@item \beta
@BES{03B2,\beta} Lower case Greek letter beta (ordinary).

@item \bigcap
@BES{22C2,\bigcap} Variable-sized, or n-ary, intersection (operator). Similar:
binary intersection@tie{}@code{\cap}.

@item \bigcirc
@BES{26AA,\bigcirc} Circle, larger (binary).  Similar: function
composition@tie{}@code{\circ}.
@c bb Best unicode symbol for this?

@item \bigcup
@BES{22C3,\bigcup} Variable-sized, or n-ary, union (operator). Similar: binary
union@tie{}@code{\cup}.

@item \bigodot
@BES{2A00,\bigodot} Variable-sized, or n-ary, circled dot operator (operator).

@item \bigoplus
@BES{2A01,\bigoplus} Variable-sized, or n-ary, circled plus operator (operator).

@item \bigotimes
@BES{2A02,\bigotimes} Variable-sized, or n-ary, circled times operator (operator).

@item \bigtriangledown
@BES{25BD,\bigtriangledown} Variable-sized, or n-ary, open triangle pointing down
(operator).

@item \bigtriangleup
@BES{25B3,\bigtriangleup} Variable-sized, or n-ary, open triangle pointing up (operator).

@item \bigsqcup
@BES{2A06,\bigsqcup} Variable-sized, or n-ary, square union (operator).

@item \biguplus
@BES{2A04,\biguplus} Variable-sized, or n-ary, union operator with a plus
(operator).  (Note that the name has only one p.)

@item \bigvee
@BES{22C1,\bigvee} Variable-sized, or n-ary, logical-and (operator).

@item \bigwedge
@BES{22C0,\bigwedge} Variable-sized, or n-ary, logical-or (operator).

@item \bot
@BESU{22A5,bot} Up tack, bottom, least element of a partially ordered
set, or a contradiction (ordinary).  See also@tie{}@code{\top}.

@item \bowtie
@BES{22C8,\bowtie} Natural join of two relations (relation).

@item \Box
@BESU{25A1,Box} Modal operator for necessity; square open box
(ordinary).  @value{NeedsAMSSymb}
@c bb Best Unicode equivalent?

@item \bullet
@cindex bullet symbol
@BES{2022,\bullet} Bullet (binary).  Similar: multiplication
dot@tie{}@code{\cdot}.

@item \cap
@BES{2229,\cap} Intersection of two sets (binary).  Similar: variable-sized
operator@tie{}@code{\bigcap}.

@item \cdot
@BES{22C5,\cdot} Multiplication (binary).  Similar: Bullet
dot@tie{}@code{\bullet}.

@item \chi
@BES{03C7,\chi} Lower case Greek chi (ordinary).

@item \circ
@BES{2218,\circ} Function composition, ring operator (binary).  Similar:
variable-sized operator@tie{}@code{\bigcirc}.

@item \clubsuit
@BES{2663,\clubsuit} Club card suit (ordinary).

@item \complement
@BESU{2201,complement} Set complement, used as a superscript as in
@code{$S^\complement$} (ordinary).  @value{NeedsAMSSymb} Also
used: @code{$S^@{\mathsf@{c@}@}$} or@tie{}@code{$\bar@{S@}$}.

@item \cong
@BES{2245,\cong} Congruent (relation).

@item \coprod
@BES{2210,\coprod} Coproduct (operator).

@item \cup
@BES{222A,\cup} Union of two sets (binary).  Similar: variable-sized
operator@tie{}@code{\bigcup}.

@item \dagger
@BES{2020,\dagger} Dagger relation (binary).

@item \dashv
@BES{22A3,\dashv} Dash with vertical, reversed turnstile (relation).  Similar:
turnstile@tie{}@code{\vdash}.

@item \ddagger
@BES{2021,\ddagger} Double dagger relation (binary).

@item \Delta
@BES{0394,\Delta} Greek upper case delta, used for increment (ordinary).

@item \delta
@BES{03B4,\delta} Greek lower case delta (ordinary).

@item \Diamond
@BESU{25C7,Diamond} Large diamond operator (ordinary).  @value{NeedsAMSSymb}
@c bb Best Unicode equivalent?

@item \diamond
@BES{22C4,\diamond} Diamond operator, or diamond bullet (binary).  Similar: large
diamond@tie{}@code{\Diamond}, circle bullet@tie{}@code{\bullet}.

@item \diamondsuit
@BES{2662,\diamondsuit} Diamond card suit (ordinary).

@item \div
@BES{00F7,\div} Division sign (binary).

@item \doteq
@BES{2250,\doteq} Approaches the limit (relation).  Similar: geometrically equal
to@tie{}@code{\Doteq}.

@item \downarrow
@BES{2193,\downarrow} Down arrow, converges (relation).  Similar: double line down
arrow@tie{}@code{\Downarrow}.

@item \Downarrow
@BES{21D3,\Downarrow} Double line down arrow (relation).  Similar: single line down
arrow@tie{}@code{\downarrow}.

@item \ell
@BES{2113,\ell} Lower-case cursive letter l (ordinary).

@item \emptyset
@BES{2205,\emptyset} Empty set symbol (ordinary).  The variant form is
@code{\varnothing}.
@c bb Why Unicode has \revemptyset but no \emptyset?
	
@item \epsilon
@BES{03F5,\epsilon} Lower case lunate epsilon (ordinary). Similar to
Greek text letter. More widely used in mathematics is the script small
letter epsilon @code{\varepsilon}@tie{}@BES{03B5,\varepsilon}. Related:
the set membership relation @code{\in}@tie{}@BES{2208,\in}.
@c src: David Carlisle http://tex.stackexchange.com/a/98018/339 and
@c Unicode referenced there asserts varepsilon is much more widely used.

@item \equiv
@BES{2261,\equiv} Equivalence (relation).

@item \eta
@BES{03B7,\eta} Lower case Greek letter (ordinary).

@item \exists
@BES{2203,\exists} Existential quantifier (ordinary).

@item \flat
@BES{266D,\flat} Musical flat (ordinary).

@item \forall
@BES{2200,\forall} Universal quantifier (ordinary).

@item \frown
@BES{2322,\frown} Downward curving arc (ordinary).

@item \Gamma
@BES{0393,\Gamma} Upper case Greek letter (ordinary).

@item \gamma
@BES{03B3,\gamma} Lower case Greek letter (ordinary).

@item \ge
@BES{2265,\ge} Greater than or equal to (relation).  This is a synonym
for@tie{}@code{\geq}.

@item \geq
@BES{2265,\geq} Greater than or equal to (relation).  This is a synonym
for@tie{}@code{\ge}.

@item \gets
@BES{2190,\gets} Is assigned the value (relation).
Synonym:@tie{}@code{\leftarrow}.

@item \gg
@BES{226B,\gg} Much greater than (relation).  Similar: much less
than@tie{}@code{\ll}.

@item \hbar
@BES{210F,\hbar} Planck constant over two pi (ordinary).

@item \heartsuit
@BES{2661,\heartsuit} Heart card suit (ordinary).

@item \hookleftarrow
@BES{21A9,\hookleftarrow} Hooked left arrow (relation).

@item \hookrightarrow
@BES{21AA,\hookrightarrow} Hooked right arrow (relation).

@item \iff
@BES{27F7,\iff} If and only if (relation).  It is @code{\Longleftrightarrow}
with a @code{\thickmuskip} on either side.

@item \Im
@BES{2111,\Im} Imaginary part (ordinary).  See: real part@tie{}@code{\Re}.

@item \in
@BES{2208,\in} Set element (relation).  See also: lower case lunate
epsilon@tie{}@code{\epsilon}@BES{03F5,\epsilon} and small letter script
epsilon@tie{}@code{\varepsilon}.

@item \infty
@BES{221E,\infty} Infinity (ordinary).

@item \int
@BES{222B,\int} Integral (operator).

@item \iota
@BES{03B9,\iota} Lower case Greek letter (ordinary).

@item \Join
@BESU{2A1D,Join} Condensed bowtie symbol (relation).  Not available in Plain
@TeX{}.

@item \kappa
@BES{03BA,\kappa} Lower case Greek letter (ordinary).

@item \Lambda
@BES{039B,\Lambda} Upper case Greek letter (ordinary).

@item \lambda
@BES{03BB,\lambda} Lower case Greek letter (ordinary).

@item \land
@BES{2227,\land} Logical and (binary).  This is a synonym for @code{\wedge}.
See also logical or@tie{}@code{\lor}.

@item \langle
@BES{27E8,\langle} Left angle, or sequence, bracket (opening).  Similar:
less-than@tie{}@code{<}. Matches@tie{}@code{\rangle}.

@item \lbrace
@BES{007B,\lbrace} Left curly brace
(opening). Synonym:@tie{}@code{\@{}. Matches@tie{}@code{\rbrace}.

@item \lbrack
@BES{005B,\lbrack} Left square bracket (opening).
Synonym:@tie{}@code{[}. Matches@tie{}@code{\rbrack}.

@item \lceil
@BES{2308,\lceil} Left ceiling bracket, like a square bracket but with the bottom
shaved off (opening). Matches@tie{}@code{\rceil}.

@item \le
@BES{2264,\le} Less than or equal to (relation).  This is a synonym
for@tie{}@code{\leq}.

@item \leadsto
@BESU{21DD,leadsto} Squiggly right arrow (relation).  @value{NeedsAMSSymb}
To get this symbol outside of math mode you can put
@code{\newcommand*@{\Leadsto@}@{\ensuremath@{\leadsto@}@}} in the
preamble and then use @code{\Leadsto} instead.
@c bb Best Unicode equivalent?

@item \Leftarrow
@BES{21D0,\Leftarrow} Is implied by, double-line left arrow (relation).  Similar:
single-line left arrow@tie{}@code{\leftarrow}.

@item \leftarrow
@BES{2190,\leftarrow} Single-line left arrow (relation).
Synonym:@tie{}@code{\gets}. Similar: double-line left
arrow@tie{}@code{\Leftarrow}.

@item \leftharpoondown
@BES{21BD,\leftharpoondown} Single-line left harpoon, barb under bar (relation).

@item \leftharpoonup
@BES{21BC,\leftharpoonup} Single-line left harpoon, barb over bar (relation).

@item \Leftrightarrow
@BES{21D4,\Leftrightarrow} Bi-implication; double-line double-headed arrow (relation).
Similar: single-line double headed arrow@tie{}@code{\leftrightarrow}.

@item \leftrightarrow
@BES{2194,\leftrightarrow} Single-line double-headed arrow (relation).  Similar:
double-line double headed arrow@tie{}@code{\Leftrightarrow}.

@item \leq
@BES{2264,\leq} Less than or equal to (relation).  This is a synonym
for@tie{}@code{\le}.

@item \lfloor
@BES{230A,\lfloor} Left floor bracket (opening). Matches:@tie{}@code{\floor}.

@item \lhd
@BESU{25C1,lhd} Arrowhead, that is, triangle, pointing left (binary).
@value{NeedsAMSSymb} For the normal subgroup symbol you should load
@file{amssymb} and use@tie{}@code{\vartriangleleft} (which is a relation
and so gives better spacing).

@item \ll
@BES{226A,\ll} Much less than (relation).  Similar: much greater
than@tie{}@code{\gg}.

@item \lnot
@BES{00AC,\lnot} Logical negation (ordinary). Synonym:@tie{}@code{\neg}.

@item \longleftarrow
@BES{27F5,\longleftarrow} Long single-line left arrow (relation).  Similar: long
double-line left arrow@tie{}@code{\Longleftarrow}.

@item \longleftrightarrow
@BES{27F7,\longleftrightarrow} Long single-line double-headed arrow (relation).  Similar: long
double-line double-headed arrow@tie{}@code{\Longleftrightarrow}.

@item \longmapsto
@BES{27FC,\longmapsto} Long single-line left arrow starting with vertical bar
(relation).  Similar: shorter version@tie{}@code{\mapsto}.

@item \longrightarrow
@BES{27F6,\longrightarrow} Long single-line right arrow (relation).  Similar: long
double-line right arrow@tie{}@code{\Longrightarrow}.

@item \lor
@BES{2228,\lor} Logical or (binary).  Synonym: wedge@tie{}@code{\wedge}. 

@item \mapsto
@BES{21A6,\mapsto} Single-line left arrow starting with vertical bar (relation).
Similar: longer version@tie{}@code{\longmapsto}.

@item \mho
@BESU{2127,mho} Conductance, half-circle rotated capital omega (ordinary).
@value{NeedsAMSSymb}

@item \mid
@BES{2223,\mid} Single-line vertical bar (relation).  A typical use of
@code{\mid} is for a set @code{\@{\, x \mid x\geq 5 \,\@}}.

Similar: @code{\vert} and@tie{}@code{|} produce the same single-line
vertical bar symbol but without any spacing (they fall in class
ordinary) and you should not use them as relations but instead only as
ordinals, i.e., footnote symbols.  For absolute value, see the entry
for@tie{}@code{\vert} and for norm see the entry for@tie{}@code{\Vert}.

@item \models
@BES{22A8,\models} Entails, or satisfies; double turnstile, short double dash
(relation).  Similar: long double dash@tie{}@code{\vDash}.

@item \mp
@BES{2213,\mp} Minus or plus (relation).

@item \mu
@BES{03BC,\mu} Lower case Greek letter (ordinary).

@item \nabla
@BES{2207,\nabla} Hamilton's del, or differential, operator (ordinary).

@item \natural
@BES{266E,\natural} Musical natural notation (ordinary).

@item \ne
@BES{2260,\ne} Not equal (relation). Synonym:@tie{}@code{\neq}.

@item \nearrow
@BES{2197,\nearrow} North-east arrow (relation).

@item \neg
@BES{00AC,\neg} Logical negation (ordinary).
Synonym:@tie{}@code{\lnot}. Sometimes instead used for
negation:@tie{}@code{\sim}.

@item \neq
@BES{2260,\neq} Not equal (relation). Synonym:@tie{}@code{\ne}.

@item \ni
@BES{220B,\ni} Reflected membership epsilon; has the member
(relation). Synonym:@tie{}@code{\owns}. Similar: is a member
of@tie{}@code{\in}.

@item \not
@BES{0020,\not}@BES{00A0,}@BES{0338,} Long solidus, or slash, used to overstrike a
following operator (relation).
@c Need blank space for it to overstrike

Many negated operators that don't require @code{\not} are available,
particularly with the @file{amssymb} package. For example, @code{\notin}
is probably typographically preferable to @code{\not\in}.

@item \notin
@BES{2209,\notin} Not an element of (relation).  Similar: not subset
of@tie{}@code{\nsubseteq}.

@item \nu
@BES{03BD,\nu} Lower case Greek letter (ordinary).

@item \nwarrow
@BES{2196,\nwarrow} North-west arrow (relation).

@item \odot
@BES{2299,\odot} Dot inside a circle (binary).  Similar: variable-sized
operator@tie{}@code{\bigodot}.

@item \oint
@BES{222E,\oint} Contour integral, integral with circle in the middle (operator).

@item \Omega
@BES{03A9,\Omega} Upper case Greek letter (ordinary).

@item \omega
@BES{03C9,\omega} Lower case Greek letter (ordinary).

@item \ominus
@BES{2296,\ominus} Minus sign, or dash, inside a circle (binary).

@item \oplus
@BES{2295,\oplus} Plus sign inside a circle (binary).  Similar: variable-sized
operator@tie{}@code{\bigoplus}.

@item \oslash
@BES{2298,\oslash} Solidus, or slash, inside a circle (binary).

@item \otimes
@BES{2297,\otimes} Times sign, or cross, inside a circle (binary).  Similar:
variable-sized operator@tie{}@code{\bigotimes}.

@item \owns
@BES{220B,\owns} Reflected membership epsilon; has the member
(relation). Synonym:@tie{}@code{\ni}. Similar: is a member
of@tie{}@code{\in}.

@item \parallel
@BES{2225,\parallel} Parallel (relation). Synonym:@tie{}@code{\|}.

@item \partial
@BES{2202,\partial} Partial differential (ordinary).

@item \perp
@BES{27C2,\perp} Perpendicular (relation).  Similar:@tie{}@code{\bot} uses the
same glyph but the spacing is different because it is in the class
ordinary.

@item \phi
@BES{03D5,\phi} Lower case Greek letter (ordinary).  The variant form is
@code{\varphi}@tie{}@BES{03C6,\varphi}.

@item \Pi
@BES{03A0,\Pi} Upper case Greek letter (ordinary).

@item \pi
@BES{03C0,\pi} Lower case Greek letter (ordinary).  The variant form is
@code{\varpi}@tie{}@BES{03D6,\varpi}.

@item \pm
@BES{00B1,\pm} Plus or minus (binary).

@item \prec
@BES{227A,\prec} Precedes (relation). Similar: less than@tie{}@code{<}.

@item \preceq
@BES{2AAF,\preceq} Precedes or equals (relation). Similar: less than or
equals@tie{}@code{\leq}.

@item \prime
@BES{2032,\prime} Prime, or minute in a time expression (ordinary).
Typically used as a superscript: @code{$f^\prime$}; @code{$f^\prime$}
and @code{$f'$} produce the same result.  An advantage of the second
is that @code{$f'''$} produces the desired symbol, that is, the same
result as @code{$f^@{\prime\prime\prime@}$}, but uses rather less
typing.  You can only use @code{\prime} in math mode.  Using the right
single quote@tie{}@code{'} in text mode produces a different character
(apostrophe).

@item \prod
@BES{220F,\prod} Product (operator).

@item \propto
@BES{221D,\propto} Is proportional to (relation)

@item \Psi
@BES{03A8,\Psi} Upper case Greek letter (ordinary).

@item \psi
@BES{03C8,\psi} Lower case Greek letter (ordinary).

@item \rangle
@BES{27E9,\rangle} Right angle, or sequence, bracket (closing). Similar: greater
than@tie{}@code{>}.  Matches:@code{\langle}.

@item \rbrace
@BES{007D,\rbrace} Right curly brace
(closing). Synonym:@tie{}@code{\@}}. Matches@tie{}@code{\lbrace}.

@item \rbrack
@BES{005D,\rbrack} Right square bracket
(closing). Synonym:@tie{}@code{]}. Matches@tie{}@code{\lbrack}.

@item \rceil
@BES{2309,\rceil} Right ceiling bracket (closing). Matches@tie{}@code{\lceil}.

@item \Re
@BES{211C,\Re} Real part, real numbers, cursive capital R (ordinary). Related:
double-line, or blackboard bold, R@tie{}@code{\mathbb@{R@}}; to access
this, load the @file{amsfonts} package.

@item \restriction
@BESU{21BE,restriction} Restriction of a function
(relation). Synonym:@tie{}@code{\upharpoonright}.  @value{NeedsAMSSymb}

@item \revemptyset
@BESU{29B0,revemptyset} Reversed empty set symbol (ordinary).  Related:
@code{\varnothing}. @value{NeedsSTIX}

@item \rfloor
@BES{230B,\rfloor} Right floor bracket, a right square bracket with the top cut
off (closing). Matches@tie{}@code{\lfloor}.

@item \rhd
@BESU{25C1,rhd} Arrowhead, that is, triangle, pointing right (binary).
@value{NeedsAMSSymb} For the normal subgroup symbol you should instead
load @file{amssymb} and use@tie{}@code{\vartriangleright} (which
is a relation and so gives better spacing).

@item \rho
@BES{03C1,\rho} Lower case Greek letter (ordinary).  The variant form is
@code{\varrho}@tie{}@BES{03F1,\varrho}.

@item \Rightarrow
@BES{21D2,\Rightarrow} Implies, right-pointing double line arrow (relation). Similar:
right single-line arrow@tie{}@code{\rightarrow}.

@item \rightarrow
@BES{2192,\rightarrow} Right-pointing single line arrow (relation). Synonym:@tie{}@code{\to}. Similar: right double line arrow@tie{}@code{\Rightarrow}.

@item \rightharpoondown
@BES{21C1,\rightharpoondown} Right-pointing harpoon with barb below the line (relation).

@item \rightharpoonup
@BES{21C0,\rightharpoonup} Right-pointing harpoon with barb above the line (relation).

@item \rightleftharpoons
@BES{21CC,\rightleftharpoons} Right harpoon up above left harpoon down (relation).

@item \searrow
@BES{2198,\searrow} Arrow pointing southeast (relation).

@item \setminus
@BES{29F5,\setminus} Set difference, reverse solidus or slash, like \
(binary). Similar: backslash@tie{}@code{\backslash} and also
@code{\textbackslash} outside of math mode.

@item \sharp
@BES{266F,\sharp} Musical sharp (ordinary).

@item \Sigma
@BES{03A3,\Sigma} Upper case Greek letter (ordinary).

@item \sigma
@BES{03C3,\sigma} Lower case Greek letter (ordinary). The variant form is
@code{\varsigma}@tie{}@BES{03C2,\varsigma}.

@item \sim
@BES{223C,\sim} Similar, in a relation (relation).

@item \simeq
@BES{2243,\simeq} Similar or equal to, in a relation (relation).

@item \smallint
@BES{222B,\smallint} Integral sign that does not change to a larger size in a
display (operator).

@item \smile
@BES{2323,\smile} Upward curving arc, smile (ordinary).

@item \spadesuit
@BES{2660,\spadesuit} Spade card suit (ordinary).

@item \sqcap
@BES{2293,\sqcap} Square intersection symbol (binary). Similar:
intersection@tie{}@code{cap}.

@item \sqcup
@BES{2294,\sqcup} Square union symbol (binary). Similar:
union@tie{}@code{cup}. Related: variable-sized
operator@tie{}@code{\bigsqcup}.

@item \sqsubset
@BESU{228F,sqsubset} Square subset symbol (relation). Similar:
subset@tie{}@code{\subset}. @value{NeedsAMSSymb}

@item \sqsubseteq
@BES{2291,\sqsubseteq} Square subset or equal symbol (binary). Similar: subset or
equal to@tie{}@code{\subseteq}.

@item \sqsupset
@BESU{2290,sqsupset} Square superset symbol (relation). Similar:
superset@tie{}@code{\supset}. @value{NeedsAMSSymb}

@item \sqsupseteq
@BES{2292,\sqsupseteq} Square superset or equal symbol (binary). Similar: superset or
equal@tie{}@code{\supseteq}.

@item \star
@BES{22C6,\star} Five-pointed star, sometimes used as a general binary operation
but sometimes reserved for cross-correlation (binary). Similar: the
synonyms asterisk@tie{}@code{*} and @code{\ast}, which are six-pointed,
and more often appear as a superscript or subscript, as with the Kleene
star.

@item \subset
@BES{2282,\subset} Subset (occasionally, is implied by) (relation).

@item \subseteq
@BES{2286,\subseteq} Subset or equal to (relation).

@item \succ
@BES{227B,\succ} Comes after, succeeds (relation). Similar: is less
than@tie{}@code{>}.

@item \succeq
@BES{2AB0,\succeq} Succeeds or is equal to (relation). Similar: less
than or equal to@tie{}@code{\leq}.

@item \sum
@BES{2211,\sum} Summation (operator). Similar: Greek capital
sigma@tie{}@code{\Sigma}.

@item \supset
@BES{2283,\supset} Superset (relation).

@item \supseteq
@BES{2287,\supseteq} Superset or equal to (relation).

@item \surd
@BES{221A,\surd} Radical symbol (ordinary).  The @LaTeX{} command
@code{\sqrt@{...@}} typesets the square root of the argument, with a bar
that extends to cover the argument.

@item \swarrow
@BES{2199,\swarrow} Southwest-pointing  arrow (relation).

@item \tau
@BES{03C4,\tau} Lower case Greek letter (ordinary).

@item \theta
@BES{03B8,\theta} Lower case Greek letter (ordinary). The variant form is
@code{\vartheta}@tie{}@BES{03D1,\vartheta}.

@item \times
@BES{00D7,\times} Primary school multiplication sign (binary). See
also@tie{}@code{\cdot}.

@item \to
@BES{2192,\to} Right-pointing single line arrow (relation).
Synonym:@tie{}@code{\rightarrow}.

@item \top
@BESU{22A4,top} Top, greatest element of a partially ordered set
(ordinary). See also@tie{}@code{\bot}.

@item \triangle
@BES{25B3,\triangle} Triangle (ordinary).

@item \triangleleft
@BES{25C1,\triangleleft} Not-filled triangle pointing left
(binary). Similar:@tie{}@code{\lhd}. For the normal subgroup symbol you
should load @file{amssymb} and use@tie{}@code{\vartriangleleft} (which
is a relation and so gives better spacing).

@item \triangleright
@BES{25B7,\triangleright} Not-filled triangle pointing right
(binary). For the normal subgroup symbol you should instead load
@file{amssymb} and use@tie{}@code{\vartriangleright} (which is a
relation and so gives better spacing).

@item \unlhd
@BESU{22B4,unlhd} Left-pointing not-filled underlined arrowhead, that
is, triangle, with a line under (binary). @value{NeedsAMSSymb}  For
the normal subgroup symbol load @file{amssymb} and
use@tie{}@code{\vartrianglelefteq} (which is a relation and so gives
better spacing).

@item \unrhd
@BESU{22B5,unrhd} Right-pointing not-filled underlined arrowhead, that
is, triangle, with a line under (binary). @value{NeedsAMSSymb}  For
the normal subgroup symbol load @file{amssymb} and
use@tie{}@code{\vartrianglerighteq} (which is a relation and so gives
better spacing).

@item \Uparrow
@BES{21D1,\Uparrow} Double-line upward-pointing arrow
(relation). Similar: single-line up-pointing
arrow@tie{}@code{\uparrow}.

@item \uparrow
@BES{2191,\uparrow} Single-line upward-pointing arrow, diverges
(relation). Similar: double-line up-pointing
arrow@tie{}@code{\Uparrow}.

@item \Updownarrow
@BES{21D5,\Updownarrow} Double-line upward-and-downward-pointing arrow
(relation). Similar: single-line upward-and-downward-pointing
arrow@tie{}@code{\updownarrow}.

@item \updownarrow
@BES{2195,\updownarrow} Single-line upward-and-downward-pointing arrow (relation). Similar:
double-line upward-and-downward-pointing arrow@tie{}@code{\Updownarrow}.

@item \upharpoonright
@BESU{21BE,upharpoonright} Up harpoon, with barb on right side
(relation). Synonym:@tie{}@code{@backslashchar{}restriction}.  @value{NeedsAMSSymb}

@item \uplus
@BES{228E,\uplus} Multiset union, a union symbol with a plus symbol in
the middle (binary). Similar: union@tie{}@code{\cup}. Related:
variable-sized operator@tie{}@code{\biguplus}.

@item \Upsilon
@BES{03A5,\Upsilon} Upper case Greek letter (ordinary).

@item \upsilon
@BES{03C5,\upsilon} Lower case Greek letter (ordinary).

@item \varepsilon
@BES{03B5,\varepsilon} Small letter script epsilon (ordinary).  This is
more widely used in mathematics than the non-variant lunate epsilon form
@code{\epsilon}@tie{}@BES{03F5,\epsilon}. Related: set
membership@tie{}@code{\in}.

@item \vanothing
@BESU{2205,varnothing} Empty set symbol. Similar:
@code{\emptyset}. Related: @code{\revemptyset}. @value{NeedsAMSSymb}

@item \varphi
@BES{03C6,\varphi} Variant on the lower case Greek letter (ordinary).
The non-variant form is @code{\phi}@tie{}@BES{03D5,\phi}.

@item \varpi
@BES{03D6,\varpi} Variant on the lower case Greek letter (ordinary).
The non-variant form is @code{\pi}@tie{}@BES{03C0,\pi}.

@item \varrho
@BES{03F1,\varrho} Variant on the lower case Greek letter (ordinary).
The non-variant form is @code{\rho}@tie{}@BES{03C1,\rho}.

@item \varsigma
@BES{03C2,\varsigma} Variant on the lower case Greek letter
(ordinary).  The non-variant form is
@code{\sigma}@tie{}@BES{03C3,\sigma}.

@item \vartheta
@BES{03D1,\vartheta} Variant on the lower case Greek letter
(ordinary).  The non-variant form is
@code{\theta}@tie{}@BES{03B8,\theta}.

@item \vdash
@BES{22A2,\vdash} Provable; turnstile, vertical and a dash
(relation). Similar: turnstile rotated a
half-circle@tie{}@code{\dashv}.

@item \vee
@BES{2228,\vee} Logical or; a downwards v shape (binary). Related:
logical and@tie{}@code{\wedge}. Similar: variable-sized
operator@tie{}@code{\bigvee}.

@item \Vert
@BES{2016,\Vert} Vertical double bar (ordinary). Similar: vertical single
bar@tie{}@code{\vert}.

For a norm symbol, you can use the @file{mathtools} package and add
@code{\DeclarePairedDelimiter\norm@{\lVert@}@{\rVert@}} to your
preamble. This gives you three command variants for double-line
vertical bars that are correctly horizontally spaced: if in the
document body you write the starred version @code{$\norm*@{M^\perp@}$}
then the height of the vertical bars will match the height of the
argument, whereas with @code{\norm@{M^\perp@}} the bars do not grow
with the height of the argument but instead are the default height,
and @code{\norm[@var{size command}]@{M^\perp@}} also gives bars that
do not grow but are set to the size given in the @var{size command},
e.g., @code{\Bigg}.

@item \vert
@BES{007C,\vert} Single line vertical bar (ordinary). Similar: double-line
vertical bar@tie{}@code{\Vert}. For such that, as in the definition of a 
set, use@tie{}@code{\mid} because it is a relation.  

For absolute value you can use the @file{mathtools} package and add
@code{\DeclarePairedDelimiter\abs@{\lvert@}@{\rvert@}} to your
preamble. This gives you three command variants for single-line vertical
bars that are correctly horizontally spaced: if in the document body you
write the starred version @code{$\abs*@{\frac@{22@}@{7@}@}$} then the
height of the vertical bars will match the height of the argument,
whereas with @code{\abs@{\frac@{22@}@{7@}@}} the bars do not grow with
the height of the argument but instead are the default height, and
@code{\abs[@var{size command}]@{\frac@{22@}@{7@}@}} also gives bars
that do not grow but are set to the size given in the @var{size
command}, e.g., @code{\Bigg}.

@item \wedge
@BES{2227,\wedge} Logical and (binary).  Synonym:@tie{}@code{\land}.  See also
logical or @code{\vee}. Similar: variable-sized
operator@tie{}@code{\bigwedge}.

@item \wp
@BES{2118,\wp} Weierstrass p (ordinary).

@item \wr
@BES{2240,\wr} Wreath product (binary).

@item \Xi
@BES{039E,\Xi} Upper case Greek letter (ordinary).

@item \xi
@BES{03BE,\xi} Lower case Greek letter (ordinary).

@item \zeta
@BES{03B6,\zeta} Lower case Greek letter (ordinary).

@end ftable


@node Math functions
@section Math functions

@cindex math functions
@cindex functions, math

These commands produce roman function names in math mode with proper
spacing.

@ftable @code
@item \arccos
@math{\arccos}

@item \arcsin
@math{\arcsin}

@item \arctan
@math{\arctan}

@item \arg
@math{\arg}

@item \bmod
Binary modulo operator (@math{x \bmod y})

@item \cos
@math{\cos}

@item \cosh
@math{\cosh}

@item \cot
@math{\cot}

@item \coth
@math{\coth}

@item \csc
@math{\csc}

@item \deg
@math{\deg}

@item \det
@math{\det}

@item \dim
@math{\dim}

@item \exp
@math{\exp}

@item \gcd
@math{\gcd}

@item \hom
@math{\hom}

@item \inf
@math{\inf}

@item \ker
@math{\ker}

@item \lg
@math{\lg}

@item \lim
@math{\lim}

@item \liminf
@math{\liminf}

@item \limsup
@math{\limsup}

@item \ln
@math{\ln}

@item \log
@math{\log}

@item \max
@math{\max}

@item \min
@math{\min}

@item \pmod
parenthesized modulus, as in (@math{\pmod 2^n - 1})

@item \Pr
@math{\Pr}

@item \sec
@math{\sec}

@item \sin
@math{\sin}

@item \sinh
@math{\sinh}

@item \sup
@iftex
@math{\mathop {\rm sup}}
@end iftex
@ifnottex
@math{\sup}
@end ifnottex
@c don't try to use \sup with dvi/pdf output since that turned into a
@c Texinfo command and it's not worth hassling with different versions
@c when it's just three roman letters anyway.

@item \tan
@math{\tan}

@item \tanh
@math{\tanh}

@end ftable


@node Math accents
@section Math accents

@cindex math accents
@cindex accents, mathematical

@LaTeX{} provides a variety of commands for producing accented letters
in math.  These are different from accents in normal text
(@pxref{Accents}).

@ftable @code
@item \acute
@cindex acute accent, math
Math acute accent: @math{\acute{x}}.

@item \bar
@cindex bar-over accent, math
@cindex macron accent, math
Math bar-over accent: @math{\bar{x}}.

@item \breve
@cindex breve accent, math
Math breve accent: @math{\breve{x}}.

@item \check
@cindex check accent, math
@cindex h@'a@v{c}ek accent, math
Math h@'a@v{c}ek (check) accent: @math{\check{x}}.

@item \ddot
@cindex double dot accent, math
Math dieresis accent: @math{\ddot{x}}.

@item \dot
@cindex overdot accent, math
@cindex dot over accent, math
Math dot accent: @math{\dot{x}}.

@item \grave
@cindex grave accent, math
Math grave accent: @math{\grave{x}}.

@item \hat
@cindex hat accent, math
@cindex circumflex accent, math
Math hat (circumflex) accent: @math{\hat{x}}.

@item \imath
@cindex dotless i, math
Math dotless i.

@item \jmath
@cindex dotless j, math
Math dotless j.

@item \mathring
@cindex ring accent, math
Math ring accent: @ringaccent{x}.  @c don't bother implementing in texinfo

@item \tilde
@cindex tilde accent, math
Math tilde accent: @math{\tilde{x}}.

@item \vec
@cindex vector symbol, math
Math vector symbol: @math{\vec{x}}.

@item \widehat
@cindex wide hat accent, math
Math wide hat accent: @math{\widehat{x+y}}.

@item \widetilde
@cindex wide tilde accent, math
Math wide tilde accent: @math{\widetilde{x+y}}.

@end ftable


@node Spacing in math mode
@section Spacing in math mode

@cindex spacing within math mode
@cindex math mode, spacing

In a @code{math} environment, @LaTeX{} ignores the spaces that you use
in the source, and instead puts in the spacing according to the normal
rules for mathematics texts.  

Many math mode spacing definitions are expressed in terms of the math unit
@dfn{mu} given by 1 em = 18 mu, where the em is taken from the current
math symbols family (@pxref{Units of length}).
@LaTeX{} provides the following commands for use in math mode:

@table @code
@item \;
@findex \;
@findex \thickspace
Normally @code{5.0mu plus 5.0mu}.  The longer name is
@code{\thickspace}.  Math mode only.

@item \:
@itemx \>
@findex \:
@findex \>
@findex \medspace
Normally @code{4.0mu plus 2.0mu minus 4.0mu}.  The longer name is
@code{\medspace}.  Math mode only.

@item \,
@findex \,
@findex \thinspace
Normally @code{3mu}.  The longer name is @code{\thinspace}.  This can
be used in both math mode and text mode. @xref{\thinspace}.

@item \!
@findex \!
A negative thin space. Normally @code{-3mu}.  Math mode only.

@item \quad
@cindex quad
@findex \quad
This is 18@dmn{mu}, that is, 1@dmn{em}. This is often used for space
surrounding equations or expressions, for instance for the space between
two equations inside a @code{displaymath} environment.  It is available
in both text and math mode.

@item \qquad
@findex \qquad
A length of 2 quads, that is, 36@dmn{mu} = 2@dmn{em}.  It is available in
both text and math mode.
@end table

In this example a thinspace separates the function from the
infinitesimal.

@example
\int_0^1 f(x)\,dx
@end example


@node Math miscellany
@section Math miscellany

@cindex math miscellany

@ftable @code
@item \*
@cindex discretionary multiplication
@cindex multiplication symbol, discretionary line break
A @dfn{discretionary} multiplication symbol, at which a line break is
allowed. Without the break multiplication is implicitly indicated by a
space, while in the case of a break a @BES{00D7,\times} symbol is
printed immediately before the break. So

@example
\documentclass@{article@}
\begin@{document@}
Now \(A_3 = 0\), hence the product of all terms \(A_1\) 
through \(A_4\), that is \(A_1\* A_2\* A_3 \* A_4\), is 
equal to zero.
\end@{document@}
@end example

will make that sort of output@c
@ifnottex
@w{ }(the ellipsis @samp{[@dots{}]} is here to show the line break at
the same place as in a @TeX{} output)@c
@end ifnottex
:

@indentedblock
Now @math{A_3 = 0},
@iftex
hence the product of all terms
@end iftex
@ifnottex
[@dots{}]
@end ifnottex
@math{A_1}
through @math{A_4}, that is @math{A_1 A_2 \times}@*@math{A_3 A_4}, is
equal to zero.
@end indentedblock

@item \cdots
A horizontal ellipsis with the dots raised to the center of the line.
@tex
As in: `$\cdots$'.
@end tex

@item \ddots
A diagonal ellipsis: @math{\ddots}.

@item \frac@{@var{num}@}@{@var{den}@}
@findex \frac
Produces the fraction @var{num} divided by @var{den}.

@ifset HAS-MATH
eg. @math{{1}\over{4}}
@end ifset

@item \left @var{delim1} ... \right @var{delim2}
@findex \right
@cindex null delimiter
The two delimiters need not match; @samp{.} acts as a @dfn{null delimiter},
producing no output.  The delimiters are sized according to the math
in between.  Example: @code{\left( \sum_@{i=1@}^@{10@} a_i \right]}.

@item \mathdollar
Dollar sign in math mode: $.

@item \mathellipsis
Ellipsis (spaced for text) in math mode: @dots{}.

@item \mathparagraph
Paragraph sign (pilcrow) in math mode: @BES{00B6,\P}.

@item \mathsection
Section sign in math mode.

@item \mathsterling
Sterling sign in math mode: @pounds{}.

@item \mathunderscore
Underscore in math mode: _.

@item \overbrace@{@var{math}@}
Generates a brace over @var{math}.
For example, @code{\overbrace@{x+\cdots+x@}^@{k \;\textrm@{times@}@}}.
@ifset HAS-MATH
The result looks like: @math{\overbrace{x+\cdots+x}^{k \rm\;times}}
@end ifset
        
@item \overline@{@var{text}@}
Generates a horizontal line over @var{tex}.
For example, @code{\overline@{x+y@}}.
@ifset HAS-MATH
The result looks like: @math{\overline{x+y}}.
@end ifset

@item \sqrt[@var{root}]@{@var{arg}@}
Produces the representation of the square root of @var{arg}.  The
optional argument @var{root} determines what root to produce.  For
example, the cube root of @code{x+y} would be typed as
@code{\sqrt[3]@{x+y@}}.
@ifset HAS-MATH
The result looks like this: @math{\root 3 \of {x+y}}.
@end ifset

@item \stackrel@{@var{text}@}@{@var{relation}@}
Puts @var{text} above @var{relation}.  For example,
@code{\stackrel@{f@}@{\longrightarrow@}}.
@ifset HAS-MATH
 The result looks like this: @math{\buildrel f \over \longrightarrow}.
@end ifset

@item \underbrace@{@var{math}@}
Generates @var{math} with a brace underneath. For example, @code{\underbrace@{x+y+z@}_@{>\,0@}}
@ifset HAS-MATH
The result looks like this: @math{\underbrace{x+y+z}_{>\,0}}.
@end ifset

@item \underline@{@var{text}@}
Causes @var{text}, which may be either math mode or not, to be
underlined.  The line is always below the text, taking account of
descenders.
@ifset HAS-MATH
The result looks like this: @math{\underline{xyz}}
@end ifset

@item \vdots
Produces a vertical ellipsis.
@ifset HAS-MATH
The result looks like this: @math{\vdots}.
@end ifset

@end ftable


@node Modes
@chapter Modes

@cindex modes
@cindex paragraph mode
@cindex math mode
@cindex left-to-right mode
@cindex LR mode

When @LaTeX{} is processing your input text, it is always in one of three
modes:

@itemize @bullet
@item
Paragraph mode
@item
Math mode
@item
Left-to-right mode, called LR mode for short
@end itemize

Mode changes occur only when entering or leaving an environment, or when
@LaTeX{} is processing the argument of certain text-producing commands.

@dfn{Paragraph mode} is the most common; it's the one @LaTeX{} is in
when processing ordinary text.  In this mode, @LaTeX{} breaks the
input text into lines and breaks the lines into pages.

@LaTeX{} is in @dfn{math mode} when it's generating a mathematical
formula, either displayed math or within a line.

@findex \mbox@r{, and LR mode}
In @dfn{LR mode}, as in paragraph mode, @LaTeX{} considers the output
that it produces to be a string of words with spaces between them.
However, unlike paragraph mode, @LaTeX{} keeps going from left to
right; it never starts a new line in LR mode.  Even if you put a
hundred words into an @code{\mbox}, @LaTeX{} would keep typesetting
them from left to right inside a single box (and then most likely
complain because the resulting box was too wide to fit on the line).
@LaTeX{} is in LR mode when it starts making a box with an
@code{\mbox} command.  You can get it to enter a different mode inside
the box---for example, you can make it enter math mode to put a
formula in the box.

There are also several text-producing commands and environments for
making a box that put @LaTeX{} into paragraph mode.  The box made by
one of these commands or environments will be called a @code{parbox}.
When @LaTeX{} is in paragraph mode while making a box, it is said to
be in ``inner paragraph mode'' (no page breaks).  Its normal paragraph
mode, which it starts out in, is called ``outer paragraph mode''.

@menu
* \ensuremath:: Ensure that math mode is active
@end menu

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

Synopsis:

@example
\ensuremath@{@var{formula}@}
@end example

The @code{\ensuremath} command ensures that @var{formula} is typeset in
math mode whatever the current mode in which the command is used.

For instance:

@example
\documentclass@{report@}
\newcommand@{\ab@}@{\ensuremath@{(\delta, \varepsilon)@}@}
\begin@{document@}
Now, the \ab\ pair is equal to \(\ab = (\frac@{1@}@{\pi@}, 0)\), ...
\end@{document@}
@end example

One can redefine commands that can be used only in math mode so that
they ca be used in any mode like in the following example given for
@code{\leadsto}:

@c Vincent 2 Karl : "Tous les chemins mènent à Rome" is a French saying
@c meaning that there are many different ways to get the same result. I
@c am not sure whether in English the given example is also funny.
@example
\documentclass@{report@}
\usepackage@{amssymb@}
\newcommand@{\originalMeaningOfLeadsTo@}@{@}
\let\originalMeaningOfLeadsTo\leadsto
\renewcommand\leadsto@{\ensuremath@{\originalMeaningOfLeadsTo@}@}
\begin@{document@}
All roads \leadsto\ Rome.
\end@{document@}
@end example


@node Page styles
@chapter Page styles

@cindex styles, page
@cindex page styles

The @code{\documentclass} command determines the size and position of
the page's head and foot.  The page style determines what goes in them.

@menu
* \maketitle::          Generate a title page.
* \pagenumbering::      Set the style used for page numbers.
* \pagestyle::		Change the headings/footings style.
* \thispagestyle::      Change the headings/footings style for this page.
@end menu


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

@cindex titles, making
@findex \maketitle

The @code{\maketitle} command generates a title on a separate title
page---except in the @code{article} class, where the title is placed
at the top of the first page.  Information used to produce the title
is obtained from the following declarations:

@ftable @code
@item \author@{@var{name} \and @var{name2}@}
@cindex author, for titlepage
@findex \\ @r{for @code{\author}}
@findex \and @r{for @code{\author}}
The @code{\author} command declares the document author(s), where the
argument is a list of authors separated by @code{\and} commands.  Use
@code{\\} to separate lines within a single author's entry---for
example, to give the author's institution or address.

@item \date@{@var{text}@}
@cindex date, for titlepage
The @code{\date} command declares @var{text} to be the document's
date.  With no @code{\date} command, the current date (@pxref{\today})
is used.

@item \thanks@{@var{text}@}
@cindex thanks, for titlepage
@cindex credit footnote
The @code{\thanks} command produces a @code{\footnote} to the title,
usually used for credit acknowledgements.

@item \title@{@var{text}@}
@cindex title, for titlepage
@findex \\ @r{for @code{\title}}
The @code{\title} command declares @var{text} to be the title of the
document.  Use @code{\\} to force a line break, as usual.

@end ftable


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

@findex \pagenumbering
@cindex page numbering style

Synopsis:

@example
\pagenumbering@{@var{style}@}
@end example

Specifies the style of page numbers, according to @var{style}; also
resets the page number to 1.  The @var{style} argument is one of
the following:

@table @code
@item arabic
arabic numerals

@item roman
lowercase Roman numerals

@item Roman
uppercase Roman numerals

@item alph
lowercase letters

@item Alph
uppercase letters
@end table


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

@findex \pagestyle
@cindex header style
@cindex footer style
@cindex running header and footer style

Synopsis:

@example
\pagestyle@{@var{style}@}
@end example

The @code{\pagestyle} command specifies how the headers and footers
are typeset from the current page onwards.  Values for @var{style}:

@table @code
@item plain
Just a plain page number.

@item empty
Empty headers and footers, e.g., no page numbers.

@item headings
Put running headers on each page.  The document style specifies what
goes in the headers.

@item myheadings
Custom headers, specified via the @code{\markboth} or the
@code{\markright} commands.

@end table

Here are the descriptions of @code{\markboth} and @code{\markright}:

@ftable @code
@item \markboth@{@var{left}@}@{@var{right}@}
Sets both the left and the right heading.  A ``left-hand heading''
(@var{left}) is generated by the last @code{\markboth} command before
the end of the page, while a ``right-hand heading'' (@var{right}) is
generated by the first @code{\markboth} or @code{\markright} that
comes on the page if there is one, otherwise by the last one before
the page.

@item \markright@{@var{right}@}
Sets the right heading, leaving the left heading unchanged.

@end ftable


@node \thispagestyle
@section @code{\thispagestyle@{@var{style}@}}

@findex \thispagestyle

The @code{\thispagestyle} command works in the same manner as the
@code{\pagestyle} command (see previous section) except that it
changes to @var{style} for the current page only.


@node Spaces
@chapter Spaces

@cindex spaces
@cindex white space

@LaTeX{} has many ways to produce white (or filled) space.

@menu
Horizontal space 
* \hspace::              Fixed horizontal space.  
* \hfill::               Stretchable horizontal space.  
* \(SPACE) and \@@::      Space after a period.  
* \(SPACE) after control sequence:: Space (gobbling) after a control sequence.
* \frenchspacing::       Equal interword and inter-sentence space.
* \thinspace::           One-sixth of an em.  
* \/::                   Insert italic correction.
* \hrulefill \dotfill::  Stretchable horizontal rule or dots.

Vertical space
* \addvspace::                    Add arbitrary vertical space if needed.
* \bigskip \medskip \smallskip::  Fixed vertical spaces.
* \vfill::                        Infinitely stretchable vertical space.
* \vspace::                       Add arbitrary vertical space.
@end menu


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

@findex \hspace

Synopsis:

@example
\hspace@{@var{length}@}
\hspace*@{@var{length}@}
@end example

Add the horizontal space given by @var{length}.  The @var{length} is a
rubber length, that is, it may contain a @code{plus} or @code{minus}
component, in any unit that @LaTeX{} understands (@pxref{Lengths}).

This command can add both positive and negative space; adding negative
space is like backspacing.

Normally when @TeX{} breaks a paragraph into lines it discards white
space (glues and kerns) that would come at the start of a line, so you
get an inter-word space or a line break between words but not both. This
command's starred version @code{\hspace*@{...@}} puts a non-discardable
invisible item in front of the space, so the space appears in the
output.

This example make a one-line paragraph that puts @samp{Name:} an inch
from the right margin.

@example
\noindent\makebox[\linewidth]@{\hspace@{\fill@}Name:\hspace@{1in@}@}
@end example


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

@findex \hfill

@cindex stretch, infinite horizontal
@cindex infinite horizontal stretch
Produce a rubber length which has
no natural space but can stretch horizontally as far as
needed (@pxref{Lengths}).

@findex \fill
The command @code{\hfill} is equivalent to @code{\hspace@{\fill@}}.  For
space that does not disappear at line breaks use
@code{\hspace*@{\fill@}} instead (@pxref{\hspace}).


@node \(SPACE) and \@@
@section @code{\(SPACE)} and \@@

@findex \(SPACE)
@findex \TAB
@findex \NEWLINE
@findex \@@
@anchor{\AT}@c old name

Mark a punctuation character, typically a period, as either ending a
sentence or as ending an abbreviation.

By default, in justifying a line @LaTeX{} adjusts the space after a
sentence-ending period (or a question mark, exclamation point, comma, or
colon) more than the space between words
(@pxref{\frenchspacing}). @LaTeX{} assumes that the period ends a
sentence unless it is preceded by a capital letter, in which case it
takes that period for part of an abbreviation.  Note that if a
sentence-ending period is immediately followed by a right parenthesis or
bracket, or right single or double quote, then the inter-sentence space
follows that parenthesis or quote.

If you have a period ending an abbreviation whose last letter is not a
capital letter, and that abbreviation is not the last word in the
sentence, then follow that period with a backslash-space (@code{\ }) or
a tie (@code{~}).  Examples are @code{Nat.\ Acad.\ Science}, and
@code{Mr.~Bean}, and @code{(manure, etc.)\ for sale}.

For another use of @code{\ }, @pxref{\(SPACE) after control sequence}.

In the opposite situation, if you have a capital letter followed by a
period that ends the sentence, then put @code{\@@} before that period.
For example, @code{book by the MAA\@@.} will have inter-sentence
spacing after the period.

In contrast, putting @code{\@@} after a period tells @TeX{} that the
period does not end the sentence.  In the example @code{reserved words
(if, then, etc.\@@) are different}, @TeX{} will put interword space
after the closing parenthesis (note that @code{\@@} is before the
parenthesis).


@node \(SPACE) after control sequence
@section @code{\ } after control sequence

The @code{\ } command is often used after control sequences to keep
them from gobbling the space that follows, as in @samp{\TeX\ is nice}.
And, under normal circumstances, @code{\}@key{tab} and
@code{\}@key{newline} are equivalent to @code{\ }. For another use of
@code{\ }, see also @ref{\(SPACE) and \@@}.

Some people prefer to use @code{@{@}} for the same purpose, as in
@code{\TeX@{@} is nice}. This has the advantage that you can always
write it the same way, namely @code{\TeX@{@}}, whether it is followed
by a space or by a punctuation mark. Compare:

@example
\TeX\ is a nice system. \TeX, a nice system.@*
\TeX@{@} is a nice system. \TeX@{@}, a nice system.
@end example

@PkgIndex{xspace}
Some individual commands, notably those defined with the @code{xspace},
package do not follow the standard behavior.


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

@findex \frenchspacing
@findex \nonfrenchspacing
@cindex spacing, inter-sentence

This declaration (from Plain @TeX{}) causes @LaTeX{} to treat
inter-sentence spacing in the same way as interword spacing.

In justifying the text in a line, some typographic traditions, including
English, prefer to adjust the space between sentences (or after other
punctuation marks) more than the space between words.  Following this
declaration, all spaces are instead treated equally.

Revert to the default behavior by declaring @code{\nonfrenchspacing}.


@node \thinspace
@section @code{\thinspace}: Insert 1/6@dmn{em}

@findex \thinspace

@code{\thinspace} produces an unbreakable and unstretchable space that
is 1/6 of an em.  This is the proper space to use between nested
quotes, as in '@dmn{}''.@c Abuse @dmn, which is a thin space in Texinfo.


@node \/
@section @code{\/}: Insert italic correction

@findex \/
@cindex italic correction

The @code{\/} command produces an @dfn{italic correction}.  This is a
small space defined by the font designer for a given character,
to avoid the character colliding with whatever follows.  The italic
@i{f} character typically has a large italic correction value.

If the following character is a period or comma, it's not necessary to
insert an italic correction, since those punctuation symbols have a
very small height.  However, with semicolons or colons, as well as
normal letters, it can help. Compare
@tex
{\it f\/: f\/;}
@end tex
@ifnottex
@i{f: f;} (in the @TeX{} output, the `f's are nicely separated)
@end ifnottex
with @i{f: f;}.

When changing fonts with commands such as @code{\textit@{italic
text@}} or @code{@{\itshape italic text@}}, @LaTeX{} will
automatically insert an italic correction if appropriate (@pxref{Font
styles}).

Despite the name, roman characters can also have an italic
correction.  Compare
@tex
pdf\/\TeX{}
@end tex
@ifnottex
pdf@TeX{} (in the @TeX{} output, there is a small space after the `f')
@end ifnottex
with pdf@TeX{}.

There is no concept of italic correction in math mode; spacing is done
in a different way.


@node \hrulefill \dotfill
@section @code{\hrulefill \dotfill}

@findex \hrulefill
@findex \dotfill

Produce an infinite rubber length (@pxref{Lengths}) filled with a
horizontal rule (that is, a line) or with dots, instead of just white
space.

When placed between blank lines this example creates a paragraph that is
left and right justified, where the space in the middle is filled with
evenly spaced dots.

@example
\noindent Jack Aubrey\dotfill Melbury Lodge
@end example

To make the rule or dots go to the line's end use @code{\null} at the
start or end.  

To change the rule's thickness, copy the definition and adjust it, as
with @code{\renewcommand@{\hrulefill@}@{\leavevmode\leaders\hrule height
1pt\hfill\kern\z@@@}}, which changes the default thickness of
0.4@dmn{pt} to 1@dmn{pt}.  Similarly, adjust the dot spacing as with
@code{\renewcommand@{\dotfill@}@{\leavevmode\cleaders\hb@@xt@@
1.00em@{\hss .\hss @}\hfill\kern\z@@@}}, which changes the default
length of 0.33@dmn{em} to 1.00@dmn{em}.


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

@findex \addvspace
@cindex vertical space
@cindex space, inserting vertical

@code{\addvspace@{@var{length}@}}

Add a vertical space of height @var{length}, which is a rubber length
(@pxref{Lengths}).  However, if vertical space has already been added to
the same point in the output by a previous @code{\addvspace} command
then this command will not add more space than what is needed to make
the natural length of the total vertical space equal to @var{length}.

Use this command to adjust the vertical space above or below an
environment that starts a new paragraph.  For instance, a Theorem
environment is defined to begin and end with @code{\addvspace@{...@}}
so that two consecutive Theorem's are separated by one vertical space,
not two.

This command is fragile (@pxref{\protect}).

The error @samp{Something's wrong--perhaps a missing \item} means that
you were not in vertical mode when you invoked this command; one way to
change that is to precede this command with a @code{\par} command.


@node \bigskip \medskip \smallskip
@section @code{\bigskip \medskip \smallskip}

These commands produce a given amount of space, specified by the
document class.

@ftable @code
@item \bigskip
@findex \bigskipamount
The same as @code{\vspace@{\bigskipamount@}}, ordinarily about one line
space, with stretch and shrink (the default for the @code{book} and
@code{article} classes is @code{12pt plus 4pt minus 4pt}).

@item \medskip
@findex \medskipamount
The same as @code{\vspace@{\medskipamount@}}, ordinarily about half of
a line space, with stretch and shrink (the default for the @code{book}
and @code{article} classes is @code{6pt plus 2pt minus 2pt}).

@item \smallskip
@findex \smallskipamount
The same as @code{\vspace@{\smallskipamount@}}, ordinarily about a
quarter of a line space, with stretch and shrink (the default for the
@code{book} and @code{article} classes is @code{3pt plus 1pt minus
1pt}).

@end ftable


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

@findex \vfill

@cindex stretch, infinite vertical
@cindex infinite vertical stretch

End the current paragraph and insert a vertical rubber length
(@pxref{Lengths}) that is infinite, so it can stretch or shrink as far
as needed.

It is often used in the same way as @code{\vspace@{\fill@}}, except that
@code{\vfill} ends the current paragraph, whereas
@code{\vspace@{\fill@}} adds the infinite vertical space below its line
irrespective of the paragraph structure.  In both cases that space will
disappear at a page boundary; to circumvent this see@tie{}@ref{\vspace}.

In this example the page is filled, so the top and bottom lines contain
the text @samp{Lost Dog!} and the third @samp{Lost Dog!} is exactly
halfway between them.
 
@example
\begin@{document@}
Lost Dog!
\vfill
Lost Dog!
\vfill
Lost Dog!
\end@{document@}
@end example


@node \vspace
@section @code{\vspace@{@var{length}@}}

@findex \vspace
@cindex vertical space
@cindex space, vertical

Synopsis, one of these two:

@example
\vspace@{@var{length}@}
\vspace*@{@var{length}@}
@end example

Add the vertical space @var{length}.  This can be negative or positive,
and is a rubber length (@pxref{Lengths}).

@LaTeX{} removes the vertical space from @code{\vspace} at a page
break, that is, at the top or bottom of a page.  The starred version
@code{\vspace*@{...@}} causes the space to stay.

If @code{\vspace} is used in the middle of a paragraph (i.e., in
horizontal mode), the space is inserted @emph{after} the line with
the @code{\vspace} command.  A new paragraph is not started.

In this example the two questions will be evenly spaced vertically on
the page, with at least one inch of space below each.

@example
\begin@{document@}
1) Who put the bomp in the bomp bah bomp bah bomp?
\vspace@{1in plus 1fill@}

2) Who put the ram in the rama lama ding dong?
\vspace@{1in plus 1fill@}
\end@{document@}
@end example


@node Boxes
@chapter Boxes

@cindex boxes

All the predefined length parameters (@pxref{Predefined lengths}) can be
used in the arguments of the box-making commands.

@menu
* \mbox::               Horizontal boxes.
* \fbox and \framebox:: Put a frame around a box.
* lrbox::               An environment like @code{\sbox}.
* \makebox::            Box, adjustable position.
* \parbox::             Box with text in paragraph mode.
* \raisebox::           Raise or lower text.
* \savebox::            Like @code{\makebox}, but save the text for later use.
* \sbox::               Like @code{\mbox}, but save the text for later use.
* \usebox::             Print saved text.
@end menu


@node \mbox
@section @code{\mbox@{@var{text@}}}

@findex \mbox

@cindex hyphenation, preventing
The @code{\mbox} command creates a box just wide enough to hold the
text created by its argument.  The @var{text} is not broken into
lines, so it can be used to prevent hyphenation.


@node \fbox and \framebox
@section @code{\fbox} and @code{\framebox}

@findex \fbox
@findex \framebox

Synopses:

@example
\fbox@{@var{text}@}
\framebox[@var{width}][@var{position}]@{@var{text}@}
@end example

The @code{\fbox} and @code{\framebox} commands are like @code{\mbox},
except that they put a frame around the outside of the box being created.

In addition, the @code{\framebox} command allows for explicit
specification of the box width with the optional @var{width} argument
(a dimension), and positioning with the optional @var{position}
argument. @c xxref

@findex \fboxrule
@findex \fboxsep
Both commands produce a rule of thickness @code{\fboxrule} (default
@samp{.4pt}), and leave a space of @code{\fboxsep} (default
@samp{3pt}) between the rule and the contents of the box.

@xref{\framebox (picture)}, for the @code{\framebox} command in the
@code{picture} environment.


@node lrbox
@section @code{lrbox}

@findex lrbox

Synopsis:

@example
\begin@{lrbox@}@{\@var{cmd}@} 
  @var{text }
\end@{lrbox@}
@end example

This is the environment form of @ref{\sbox,@code{\sbox}}.

The @var{text} inside the environment is saved in the box @code{\@var{cmd}},
which must have been declared with @code{\newsavebox}.


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

@findex \makebox

Synopsis:

@example
\makebox[@var{width}][@var{position}]@{@var{text}@}
@end example

The @code{\makebox} command creates a box just wide enough to contain
the @var{text} specified.  The width of the box can be overridden by the
optional @var{width} argument.  The position of the text within the box
is determined by the optional @var{position} argument, which may take
the following values:

@table @code
@item c
Centered (default).
@item l
Flush left.
@item r
Flush right.
@item s
Stretch (justify) across entire @var{width}; @var{text} must contain
stretchable space for this to work.
@end table

@code{\makebox} is also used within the @code{picture} environment
@pxref{\makebox (picture)}.


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

@findex \parbox

Synopsis:

@example
\parbox[@var{position}][@var{height}][@var{inner-pos}]@{@var{width}@}@{@var{text}@}
@end example

@cindex paragraph mode
The @code{\parbox} command produces a box whose contents are created
in @dfn{paragraph mode}.  It should be used to make a box small
pieces of text, with nothing fancy inside.  In particular, you
shouldn't use any paragraph-making environments inside a
@code{\parbox} argument.  For larger pieces of text, including ones
containing a paragraph-making environment, you should use a
@code{minipage} environment (@pxref{minipage}).

@code{\parbox} has two mandatory arguments:

@table @var
@item width
the width of the parbox;
@item text
the text that goes inside the parbox.
@end table

By default @LaTeX{} will position vertically a parbox so its center
lines up with the center of the surrounding text line.  When the
optional @var{position} argument is present and equal either to @samp{t}
or @samp{b}, this allows you respectively to align either the top or
bottom line in the parbox with the baseline of the surrounding text. You
may also specify @samp{m} for @var{position} to get the default
behaviour.

The optional @var{height} argument overrides the natural height of the box.

The @var{inner-pos} argument controls the placement of the text inside
the box, as follows; if it is not specified, @var{position} is used.

@table @code
@item t
text is placed at the top of the box.
@item c
text is centered in the box.
@item b
text is placed at the bottom of the box.
@item s
stretch vertically; the text must contain vertically stretchable space
for this to work.
@end table


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

@findex \raisebox

Synopsis:

@example
\raisebox@{@var{distance}@}[@var{height}][@var{depth}]@{@var{text}@}
@end example

The @code{\raisebox} command raises or lowers @var{text}.  The first
mandatory argument specifies how high @var{text} is to be raised (or
lowered if it is a negative amount).  @var{text} itself is processed
in LR mode.

The optional arguments @var{height} and @var{depth} are dimensions.  If
they are specified, @LaTeX{} treats @var{text} as extending a certain
distance above the baseline (@var{height}) or below (@var{depth}),
ignoring its natural height and depth.


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

@findex \savebox

Synopsis:

@example
\savebox@{@var{\boxcmd}@}[@var{width}][@var{pos}]@{@var{text}@}
@end example

This command typeset @var{text} in a box just as with @code{\makebox}
(@pxref{\makebox}), except that instead of printing the resulting box,
it saves it in the box labeled @var{\boxcmd}, which must have been
declared with @code{\newsavebox} (@pxref{\newsavebox}).


@node \sbox
@section @code{\sbox@{@var{\boxcmd}@}@{@var{text}@}}

@findex \sbox

Synopsis:

@example
\sbox@{@var{\boxcmd}@}@{@var{text}@}
@end example

@code{\sbox} types @var{text} in a box just as with @code{\mbox}
(@pxref{\mbox}) except that instead of the resulting box being
included in the normal output, it is saved in the box labeled
@var{\boxcmd}.  @var{\boxcmd} must have been previously declared with
@code{\newsavebox} (@pxref{\newsavebox}).


@node \usebox
@section @code{\usebox@{@var{\boxcmd}@}}

@findex \usebox

Synopsis:

@example
\usebox@{@var{\boxcmd}@}
@end example

@code{\usebox} produces the box most recently saved in the bin
@var{\boxcmd} by a @code{\savebox} command (@pxref{\savebox}).


@node Special insertions
@chapter Special insertions

@cindex special insertions
@cindex insertions of special characters

@LaTeX{} provides commands for inserting characters that have a
special meaning do not correspond to simple characters you can type.

@menu
* Reserved characters::         Inserting @samp{# $ % & @{ @} _ ~ ^ \}
* Upper and lower case::        Make text upper or lower case.
* Symbols by font position::    Inserting font symbols by number.
* Text symbols::                Inserting other non-letter symbols in text.
* Accents::                     Inserting accents.
* Additional Latin letters::      Inserting other non-English characters.
* \rule::                       Inserting lines and rectangles.
* \today::                      Inserting today's date.
@end menu


@node Reserved characters
@section Reserved characters

@cindex reserved characters
@cindex characters, reserved
@cindex special characters
@cindex characters, special
@LaTeX{} sets aside the following characters for special purposes (for
example, the percent sign@tie{}@code{%} is for comments) so they are
called @dfn{reserved characters} or @dfn{special characters}.

@example
# $ % & @{ @} _ ~ ^ \ 
@end example

@findex \#
@findex \$
@findex \%
@findex \&
@findex \_
@findex \@{
@findex \@}
If you want a reserved character to be printed as itself, in the text
body font, for all but the final three characters in that list simply
put a backslash@tie{}@code{\} in front of the character.  Thus,
@code{\$1.23} will produce@tie{}@code{$1.23} in your output.

@findex \~
@findex \^ 
@findex \textbackslash
As to the last three characters, to get a tilde in the text body font
use @code{\~@{@}} (omitting the curly braces would result in the next
character receiving a tilde accent).  Similarly, to get a get a text
body font circumflex use @code{\^@{@}}.  A text body font backslash
results from @code{\textbackslash@{@}}.

To produce the reserved characters in a typewriter font use
@code{\verb!!}, as below.

@example
\begin@{center@}
  \# \$ \% \& \@{ \@} \_ \~@{@} \^@{@} \textbackslash \\
  \verb!# $ % & @{ @} _ ~ ^ \!
\end@{center@}
@end example

In that example the double backslash@tie{}@code{\\} is only there to
split the lines.


@node Upper and lower case
@section Upper and lower case

@cindex Upper case
@cindex Lower case
@cindex characters, case

Synopsis:

@example
\uppercase@{@var{text}@}
\lowercase@{@var{text}@}
\MakeUppercase@{@var{text}@}
\MakeLowercase@{@var{text}@}
@end example

Change the case of characters.  The @TeX{} primitives commands
@code{\uppercase} and @code{\lowercase} only work for American
characters. The @LaTeX{} commands @code{\MakeUppercase} and
@code{\MakeLowercase} commands also change characters accessed by
commands such as @code{\ae} or @code{\aa}.  The commands
@code{\MakeUppercase} and @code{\MakeLowercase} are robust but they have
moving arguments (@pxref{\protect}).

These commands do not change the case of letters used in the name of a
command within @var{text}.  But they do change the case of every other
latin character inside the argument @var{text}.  Thus,
@code{\MakeUppercase@{Let $y=f(x)$}@} produces ``LET Y=F(X)''.  Another
example is that the name of an environment will be changed, so that
@code{\MakeUppercase@{\begin@{tabular@} ... \end@{tabular@}} will
produce an error because the first half is changed to
@code{\begin@{TABULAR@}}.

@LaTeX{} uses the same fixed table for changing case throughout a
document, The table used is designed for the font encoding T1; this
works well with the standard @TeX{} fonts for all Latin alphabets but
will cause problems when using other alphabets.

To change the case of text that results from a command inside @var{text}
you need to do expansion.  Here the @code{\Schoolname} produces
``COLLEGE OF MATHEMATICS''.

@example
\newcommand@{\schoolname@}@{College of Mathematics@}
\newcommand@{\Schoolname@}@{\expandafter\MakeUppercase\expandafter@{\schoolname@}@}
@end example

To uppercase only the first letter of words use the package
@file{mfirstuc}.


@node Symbols by font position
@section Symbols by font position

@findex \symbol
@cindex accessing any character of a font
@cindex font symbols, by number

You can access any character of the current font using its number with
the @code{\symbol} command. For example, the visible space character
used in the @code{\verb*} command has the code decimal 32, so it can be
typed as @code{\symbol@{32@}}.

You can also specify numbers in octal (base 8) by using a @code{'}
prefix, or hexadecimal (base 16) with a @code{"} prefix, so the previous
example could also be written as @code{\symbol@{'40@}} or
@code{\symbol@{"20@}}.


@node Text symbols
@section Text symbols

@cindex text symbols
@cindex symbols, text

@findex textcomp @r{package}
@LaTeX{} provides commands to generate a number of non-letter symbols
in running text.  Some of these, especially the more obscure ones, are
not available in OT1; you may need to load the @code{textcomp} package.

@ftable @code
@item \copyright
@itemx \textcopyright
@cindex copyright symbol
The copyright symbol, @copyright{}.

@item \dag
@cindex dagger, in text
The dagger symbol (in text).

@item \ddag
@cindex double dagger, in text
The double dagger symbol (in text).

@item \LaTeX
@cindex @LaTeX{} logo
@cindex logo, @LaTeX{}
The @LaTeX{} logo.

@item \LaTeXe
@cindex @LaTeX{}2e logo
@cindex logo, @LaTeX{}2e
The @LaTeX{}2e logo.

@item \guillemotleft @r{(@guillemotleft{})}
@itemx \guillemotright @r{(@guillemotright{})}
@itemx \guilsinglleft @r{(@guilsinglleft{})}
@itemx \guilsinglright @r{(@guilsinglright{})}
@cindex double guillemets
@cindex single guillemets
@cindex left angle quotation marks
@cindex right angle quotation marks
@cindex double angle quotation marks
@cindex single angle quotation marks
@cindex French quotation marks
@cindex quotation marks, French
Double and single angle quotation marks, commonly used in French:
@guillemotleft{}, @guillemotright{}, @guilsinglleft{}, @guilsinglright{}.

@item \ldots
@itemx \dots
@itemx \textellipsis
@cindex ellipsis
An ellipsis (three dots at the baseline): `@dots{}'.  @code{\ldots}
and @code{\dots} also work in math mode.

@item \lq
@cindex left quote
@cindex opening quote
Left (opening) quote: `.

@item \P
@itemx \textparagraph
@cindex paragraph symbol
@cindex pilcrow
Paragraph sign (pilcrow): @BES{00B6,\P}.

@item \pounds
@itemx \textsterling
@cindex pounds symbol
@cindex sterling symbol
English pounds sterling: @pounds{}.

@item \quotedblbase @r{(@quotedblbase{})}
@itemx \quotesinglbase @r{(@quotesinglbase{})}
@cindex double low-9 quotation mark
@cindex single low-9 quotation mark
@cindex low-9 quotation marks, single and double
Double and single quotation marks on the baseline:
@quotedblbase{} and @quotesinglbase{}.

@item \rq
@cindex right quote
@cindex closing quote
Right (closing) quote: '.

@item \S
\itemx \textsection
@cindex section symbol
Section sign: @BES{00A7,\S}.

@item \TeX
@cindex @TeX{} logo
@cindex logo, @TeX{}
The @TeX{} logo.

@item \textasciicircum
@cindex circumflex, ASCII, in text
@cindex ASCII circumflex, in text
ASCII circumflex: ^.

@item \textasciitilde
@cindex tilde, ASCII, in text
@cindex ASCII tilde, in text
ASCII tilde: ~.

@item \textasteriskcentered
@cindex asterisk, centered, in text
@cindex centered asterisk, in text
Centered asterisk: *.

@item \textbackslash
@cindex backslash, in text
Backslash: \.

@item \textbar
@cindex vertical bar, in text
@cindex bar, vertical, in text
Vertical bar: |.

@item \textbardbl
@cindex vertical bar, double, in text
@cindex bar, double vertical, in text
@cindex double vertical bar, in text
Double vertical bar.

@item \textbigcircle
@cindex big circle symbols, in text
@cindex circle symbol, big, in text
Big circle symbol.

@item \textbraceleft
@cindex left brace, in text
@cindex brace, left, in text
Left brace: @{.

@item \textbraceright
@cindex right brace, in text
@cindex brace, right, in text
Right brace: @}.

@item \textbullet
@cindex bullet, in text
Bullet: @bullet{}.

@item \textcircled@{@var{letter}@}
@cindex circled letter, in text
@var{letter} in a circle, as in @registeredsymbol{}.

@item \textcompwordmark
@itemx \textcapitalcompwordmark
@itemx \textascendercompwordmark
@cindex composite word mark, in text
@cindex cap height
@cindex ascender height
Composite word mark (invisible).  The @code{\textcapital...} form
has the cap height of the font, while the @code{\textascender...} form
has the ascender height.

@item \textdagger
@cindex dagger, in text
Dagger: @math{\dag}.

@item \textdaggerdbl
@cindex dagger, double, in text
@cindex double dagger, in text
Double dagger: @math{\ddag}.

@item \textdollar @r{(or @code{\$})}
@cindex dollar sign
@cindex currency, dollar
Dollar sign: $.

@item \textemdash @r{(or @code{---})}
@cindex em-dash
Em-dash: --- (for punctuation).

@item \textendash @r{(or @code{--})}
@cindex e-dash
En-dash: -- (for ranges).

@item \texteuro
@cindex euro symbol
@cindex currency, euro
The Euro symbol: @euro{}.

@item \textexclamdown @r{(or @code{!`})}
@cindex exclamation point, upside-down
Upside down exclamation point: @exclamdown{}.

@item \textgreater
@cindex greater than symbol, in text
Greater than: >.

@item \textless
@cindex less than symbol, in text
Less than: <.

@item \textleftarrow
@cindex arrow, left, in text
@cindex left arrow, in text
Left arrow.

@item \textordfeminine
@itemx \textordmasculine
@cindex feminine ordinal symbol
@cindex masculine ordinal symbol
@cindex ordinals, feminine and masculine
@cindex Spanish ordinals, feminine and masculine
Feminine and masculine ordinal symbols: @ordf{}, @ordm{}.

@item \textperiodcentered
@cindex period, centered, in text
@cindex centered period, in text
Centered period: @BES{00B7,\cdot}.

@item \textquestiondown @r{(or @code{?`})}
@cindex question mark, upside-down
Upside down question mark: @questiondown{}.

@item \textquotedblleft @r{(or @code{``})}
@cindex left quote, double
@cindex double left quote
Double left quote: ``.

@item \textquotedblright @r{(or @code{''})}
@cindex right quote, double
@cindex double right quote
Double right quote: ''.

@item \textquoteleft @r{(or @code{`})}
@cindex left quote, single
@cindex single left quote
Single left quote: `.

@item \textquoteright @r{(or @code{'})}
@cindex right quote, single
@cindex single right quote
Single right quote: '.

@item \textquotesingle
@cindex quote, single straight
@cindex straight single quote
@cindex single quote, straight
Straight single quote.  (From TS1 encoding.)

@item \textquotestraightbase
@itemx \textquotestraightdblbase
@cindex quote, straight base
@cindex straight quote, base
@cindex double quote, straight base
@cindex straight double quote, base
Single and double straight quotes on the baseline.

@item \textregistered
@cindex registered symbol
Registered symbol: @registeredsymbol{}.

@item \textrightarrow
@cindex arrow, right, in text
@cindex right arrow, in text
Right arrow.

@item \textthreequartersemdash
@cindex three-quarters em-dash
@cindex em-dash, three-quarters
``Three-quarters'' em-dash, between en-dash and em-dash.

@item \texttrademark
@cindex trademark symbol
Trademark symbol: @BES{2122,^{\hbox{TM}}}.

@item \texttwelveudash
@cindex two-thirds em-dash
@cindex em-dash, two-thirds
``Two-thirds'' em-dash, between en-dash and em-dash.

@item \textunderscore
@cindex underscore, in text
Underscore: _.

@item \textvisiblespace
@cindex visible space symbol, in text
Visible space symbol.

@end ftable


@node Accents
@section Accents

@cindex accents
@cindex characters, accented
@cindex letters, accented

@PkgIndex{babel}
@cindex multilingual support
@LaTeX{} has wide support for many of the world's scripts and
languages, through the @code{babel} package and related support.  This
section does not attempt to cover all that support.  It merely lists
the core @LaTeX{} commands for creating accented characters.

The @code{\capital...} commands produce alternative forms for use with
capital letters.  These are not available with OT1.

@table @code
@item \"
@itemx \capitaldieresis
@findex \" @r{(umlaut accent)}
@findex \capitaldieresis
@cindex umlaut accent
@cindex dieresis accent
Produces an umlaut (dieresis), as in @"{o}.

@item \'
@itemx \capitalacute
@findex \' @r{(acute accent)}
@findex \capitalacute
@cindex acute accent
Produces an acute accent, as in @'{o}.  In the @code{tabbing}
environment, pushes current column to the right of the previous column
(@pxref{tabbing}).

@item \.
@findex \. @r{(dot-over accent)}
@cindex dot accent
@cindex dot-over accent
Produces a dot accent over the following, as in @dotaccent{o}.

@item \=
@itemx \capitalmacron
@findex \= @r{(macron accent)}
@findex \capitalmacron
@cindex macron accent
@cindex overbar accent
@cindex bar-over accent
Produces a macron (overbar) accent over the following, as in @={o}.

@item \^
@itemx \capitalcircumflex
@findex \^ @r{(circumflex accent)}
@findex \capitalcircumflex
@cindex circumflex accent
@cindex hat accent
Produces a circumflex (hat) accent over the following, as in @^{o}.

@item \`
@itemx \capitalgrave
@findex \` @r{(grave accent)}
@findex \capitalgrave
@cindex grave accent
Produces a grave accent over the following, as in @`{o}.  In the
@code{tabbing} environment, move following text to the right margin
(@pxref{tabbing}).

@item \~
@itemx \capitaltilde
@findex \~ @r{(tilde accent)}
@findex \capitaltilde
@cindex tilde accent
Produces a tilde accent over the following, as in @~{n}.

@item \b
@findex \b @r{(bar-under accent)}
@cindex bar-under accent
Produces a bar accent under the following, as in @ubaraccent{o}. See
also @code{\underbar} hereinafter.

@item \c
@itemx \capitalcedilla
@findex \c @r{(cedilla accent)}
@findex \capitalcedilla
@cindex cedilla accent
Produces a cedilla accent under the following, as in @,{c}.

@item \d
@itemx \capitaldotaccent
@findex \d @r{(dot-under accent)}
@findex \capitaldotaccent
@cindex dot-under accent
Produces a dot accent under the following, as in @udotaccent{o}.

@item \H
@itemx \capitalhungarumlaut
@findex \H @r{(Hungarian umlaut accent)}
@findex \capitalhungarumlaut
@cindex hungarian umlaut accent
Produces a long Hungarian umlaut accent over the following, as in @H{o}.

@item \i
@findex \i @r{(dotless i)}
@cindex dotless i
Produces a dotless i, as in `@dotless{i}'.

@item \j
@findex \j @r{(dotless j)}
@cindex dotless j
Produces a dotless j, as in `@dotless{j}'.

@item \k
@itemx \capitalogonek
@findex \k @r{(ogonek)}
@findex \capitalogonek
@cindex ogonek
Produces a letter with ogonek, as in `@ogonek{o}'.  Not available in
the OT1 encoding.

@item \r
@itemx \capitalring
@findex \r @r{(ring accent)}
@findex \capitalring
@cindex ring accent
Produces a ring accent, as in `@ringaccent{o}'.

@item \t
@itemx \capitaltie
@itemx \newtie
@itemx \capitalnewtie
@findex \t @r{(tie-after accent)}
@findex \capitaltie
@findex \newtie
@findex \capitalnewtie
@cindex tie-after accent
Produces a tie-after accent, as in `@tieaccent{oo}'.  The
@code{\newtie} form is centered in its box.

@item \u
@itemx \capitalbreve
@findex \u @r{(breve accent)}
@findex \capitalbreve
@cindex breve accent
Produces a breve accent, as in `@u{o}'.

@item \underbar
@findex \underbar
@cindex underbar
Not exactly an accent, this produces a bar under the argument text.
The argument is always processed in horizontal mode.  The bar is
always a fixed position under the baseline, thus crossing through
descenders.  See also @code{\underline} in @ref{Math miscellany}.
See also @code{\b} above.

@item \v
@itemx \capitalcaron
@findex \v @r{(breve accent)}
@findex \capitalcaron
@cindex hacek accent
@cindex check accent
@cindex caron accent
Produces a h@'a@v{c}ek (check, caron) accent, as in `@v{o}'.

@end table


@node Additional Latin letters
@section Additional Latin letters

@anchor{Non-English characters}
@cindex Latin letters, additional
@cindex letters, additional Latin
@cindex extended Latin 
@cindex special characters
@cindex non-English characters
@cindex characters, non-English

Here are the basic @LaTeX{} commands for inserting letters (beyond
A--Z) extending the Latin alphabet, used primarily in languages other
than English.

@table @code
@item \aa
@itemx \AA
@findex \aa (@aa{})
@findex \AA (@AA{})
@cindex aring
@aa{} and @AA{}.

@item \ae
@itemx \AE
@findex \ae (@ae{})
@findex \AE (@AE{})
@cindex ae ligature
@ae{} and @AE{}.

@item \dh
@itemx \DH
@findex \dh (@dh{})
@findex \DH (@DH{})
@cindex Icelandic eth
@cindex eth, Icelandic letter
Icelandic letter eth: @dh{} and @DH{}. Not available with @sc{OT1}
encoding, you need the @file{fontenc} package to select an alternate
font encoding, such as @sc{T1}.

@item \dj
@itemx \DJ
@findex \dj
@findex \DJ
Crossed d and D, a.k.a.@: capital and small letter d with stroke.  Not
available with @sc{OT1} encoding, you need the @file{fontenc} package to
select an alternate font encoding, such as @sc{T1}.

@item \ij
@itemx \IJ
@findex \ij (ij)
@findex \IJ (IJ)
@cindex ij letter, Dutch
ij and IJ (except somewhat closer together than appears here).

@item \l
@itemx \L
@findex \l (@l{})
@findex \L (@L{})
@cindex polish l
@l{} and @L{}.

@item \ng
@itemx \NG
@findex \ng
@findex \NG
Lappish letter eng, also used in phonetics.

@item \o
@itemx \O
@findex \o (@o{})
@findex \O (@O{})
@cindex oslash
@o{} and @O{}.

@item \oe
@itemx \OE
@findex \oe (@oe{})
@findex \OE (@OE{})
@cindex oe ligature
@oe{} and @OE{}.

@item \ss
@itemx \SS
@findex \ss (@ss{})
@findex \SS (SS)
@cindex es-zet German letter
@cindex sharp S letters
@ss{} and SS.

@item \th
@itemx \TH
@findex \th (@th{})
@findex \TH (@TH{})
@cindex Icelandic thorn
@cindex thorn, Icelandic letter
Icelandic letter thorn: @th{} and @TH{}. Not available with @sc{OT1}
encoding, you need the @file{fontenc} package to select an alternate
font encoding, such as @sc{T1}.

@end table


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

@findex \rule

Synopsis:

@example
\rule[@var{raise}]@{@var{width}@}@{@var{thickness}@}
@end example

The @code{\rule} command produces @dfn{rules}, that is, lines or
rectangles.  The arguments are:

@table @var
@item raise
How high to raise the rule (optional).

@item width
The length of the rule (mandatory).

@item thickness
The thickness of the rule (mandatory).
@end table


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

@findex \today
@cindex date, today's

The @code{\today} command produces today's date, in the format
@samp{@var{month} @var{dd}, @var{yyyy}}; for example, @samp{July 4, 1976}.
It uses the predefined counters @code{\day}, @code{\month}, and
@code{\year} (@pxref{\day \month \year}) to do this.  It is not
updated as the program runs.

Multilingual packages like @file{babel} or classes like @file{lettre},
among others, will localize @code{\today}. For example, the following
will output @samp{4 juillet 1976}:

@example
\year=1976 \month=7 \day=4
\documentclass@{minimal@}
\usepackage[french]@{babel@}
\begin@{document@}
\today
\end@{document@}
@end example

@PkgIndex{datetime}
The @code{datetime} package, among others, can produce a wide variety
of other date formats.


@node Splitting the input
@chapter Splitting the input

@cindex splitting the input file
@cindex input file

A large document requires a lot of input.  Rather than putting the whole
input in a single large file, it's more efficient to split it into
several smaller ones.  Regardless of how many separate files you use,
there is one that is the 
@cindex root file
@cindex file, root
@dfn{root file}; it is the one whose name you type
when you run @LaTeX{}.

@xref{filecontents}, for an environment that allows bundling an
external file to be created with the main document.

@menu
* \include::            Conditionally include a file.
* \includeonly::        Determine which files are included.
* \input::              Unconditionally include a file.
@end menu


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

@findex \include

Synopsis:

@example
\include@{@var{file}@}
@end example

If no @code{\includeonly} command is present, the @code{\include}
command executes @code{\clearpage} to start a new page
(@pxref{\clearpage}), then reads @var{file}, then does another
@code{\clearpage}.

Given an @code{\includeonly} command, the @code{\include} actions are
only run if @var{file} is listed as an argument to
@code{\includeonly}.  See @ref{\includeonly}.

@cindex nested @code{\include}, not allowed
The @code{\include} command may not appear in the preamble or in a file
read by another @code{\include} command.


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

@findex \includeonly

Synopsis:

@example
\includeonly@{@var{file1},@var{file2},...@}
@end example

The @code{\includeonly} command controls which files will be read by
subsequent @code{\include} commands.  The list of filenames is
comma-separated. Each element @var{file1}, @var{file2}, @dots{} must
exactly match a filename specified in a @code{\include} command for the
selection to be effective.

This command can only appear in the preamble.


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

@findex \input

Synopsis:

@example
\input@{@var{file}@}
@end example

The @code{\input} command causes the specified @var{file} to be read
and processed, as if its contents had been inserted in the current
file at that point.

If @var{file} does not end in @samp{.tex} (e.g., @samp{foo} or
@samp{foo.bar}), it is first tried with that extension (@samp{foo.tex}
or @samp{foo.bar.tex}).  If that is not found, the original @var{file}
is tried (@samp{foo} or @samp{foo.bar}).


@node Front/back matter
@chapter Front/back matter

@menu
* Tables of contents::
* Glossaries::
* Indexes::
@end menu


@node Tables of contents
@section Tables of contents

@cindex table of contents, creating

@findex \tableofcontents
@findex .toc @r{file}
A table of contents is produced with the @code{\tableofcontents}
command.  You put the command right where you want the table of
contents to go; @LaTeX{} does the rest for you.  A previous run must
have generated a @file{.toc} file.

The @code{\tableofcontents} command produces a heading, but it does
not automatically start a new page.  If you want a new page after the
table of contents, write a @code{\newpage} command after the
@code{\tableofcontents} command.

@findex \listoffigures
@findex \listoftables
@findex .lof @r{file}
@findex .lot @r{file}
The analogous commands @code{\listoffigures} and @code{\listoftables}
produce a list of figures and a list of tables (from @file{.lof} and
@file{.lot} files), respectively.  Everything works exactly the same
as for the table of contents.

@findex \nofiles
The command @code{\nofiles} overrides these commands, and
@emph{prevents} any of these lists from being generated.

@menu
* \addcontentsline::    Add an entry to table of contents, etc.
* \addtocontents::      Add text directly to table of contents file, etc.
@end menu


@node \addcontentsline
@subsection @code{\addcontentsline}

@findex \addcontentsline
@cindex table of contents entry, manually adding

Synopsis:

@example
\addcontentsline@{@var{ext}@}@{@var{unit}@}@{@var{text}@}
@end example

The @code{\addcontentsline} command adds an entry to the specified list
or table where:

@table @var
@item ext
The filename extension of the file on which information is to be written,
typically one of: @code{toc} (table of contents), @code{lof} (list of
figures), or @code{lot} (list of tables).

@item unit
The name of the sectional unit being added, typically one of the
following, matching the value of the @var{ext} argument:

@table @code
@item toc
The name of the sectional unit: @code{part}, @code{chapter},
@code{section}, @code{subsection}, @code{subsubsection}.
@item lof
For the list of figures: @code{figure}.
@item lot
For the list of tables: @code{table}.
@end table

@item text
The text of the entry.
@end table

@findex \contentsline
What is written to the @file{.@var{ext}} file is the command
@code{\contentsline@{@var{unit}@}@{@var{text}@}@{@var{num}@}}, where
@code{@var{num}} is the current value of counter @code{@var{unit}}.

@c xx how hardwired are these values?  other unit names?


@node \addtocontents
@subsection @code{\addtocontents}

@findex \addtocontents@{@var{ext}@}@{@var{text}@}

The @code{\addtocontents}@{@var{ext}@}@{@var{text}@} command adds text
(or formatting commands) directly to the @file{.@var{ext}} file that
generates the table of contents or lists of figures or tables.

@table @var
@item ext
The extension of the file on which information is to be written,
typically one of: @file{toc} (table of contents), @file{lof} (list of
figures), or @file{lot} (list of tables).

@item text
The text to be written.
@end table


@node Glossaries
@section Glossaries

@cindex glossaries

@findex \makeglossary
The command @code{\makeglossary} enables creating glossaries.

@findex \glossary
@cindex @file{.glo} file
The command @code{\glossary@{@var{text}@}} writes a glossary entry for
@var{text} to an auxiliary file with the @file{.glo} extension.

@findex \glossaryentry
Specifically, what gets written is the command
@code{\glossaryentry@{@var{text}@}@{@var{pageno}@}}, where
@var{pageno} is the current @code{\thepage} value.

@cindex glossary @r{package}
The @code{glossary} package on CTAN provides support for fancier
glossaries.


@node Indexes
@section Indexes

@cindex indexes

@findex \makeindex
The command @code{\makeindex} enables creating indexes.  Put this in
the preamble.

@findex \index
@cindex @file{.idx} file
The command @code{\index@{@var{text}@}} writes an index entry for
@var{text} to an auxiliary file named with the @file{.idx} extension.

@findex \indexentry
Specifically, what gets written is the command
@code{\indexentry@{@var{text}@}@{@var{pageno}@}}, where @var{pageno}
is the current @code{\thepage} value.

@cindex `see' and `see also' index entries
@cindex  index entries, `see' and `see also'
To generate a index entry for `bar' that says `See foo', use a
vertical bar: @code{\index@{bar|see@{foo@}@}}.  Use @code{seealso}
instead of @code{see} to make a `See also' entry.

@findex \seename
@findex \alsoname
The text `See' is defined by the macro @code{\seename}, and `See also'
by the macro @code{\alsoname}.  These can be redefined for other
languages.

@cindex @command{makeindex} program
@cindex @command{xindy} program
@cindex @file{.ind} file
The generated @file{.idx} file is then sorted with an external
command, usually either @command{makeindex}
(@url{http://mirror.ctan.org/indexing/makeindex}) or (the
multi-lingual) @command{xindy} (@url{http://xindy.sourceforge.net}).
This results in a @file{.ind} file, which can then be read to typeset
the index.

@findex \printindex
@PkgIndex{makeidx}
The index is usually generated with the @code{\printindex} command.
This is defined in the @code{makeidx} package, so
@code{\usepackage@{makeidx@}} needs to be in the preamble.

@findex \indexspace
The rubber length @code{\indexspace} is inserted before each new
letter in the printed index; its default value is @samp{10pt plus5pt
minus3pt}.

@PkgIndex{showidx}
The @code{showidx} package causes each index entries to be shown in
the margin on the page where the entry appears.  This can help in
preparing the index.

@PkgIndex{multind}
The @code{multind} package supports multiple indexes.  See also the
@TeX{} FAQ entry on this topic,
@url{http://www.tex.ac.uk/cgi-bin/texfaq2html?label=multind}.


@node Letters
@chapter Letters

@cindex letters, writing
@cindex writing letters

Synopsis: 

@example
\documentclass@{letter@}
\address@{@var{sender address}@}
\signature@{@var{sender name}@}
\begin@{document@}
\begin@{letter@}@{@var{recipient address}@}
\opening@{@var{salutation}@}
  @var{letter body}
\closing@{@var{closing text}@}
\end@{letter@}
...  more letters ...
\end@{document@}
@end example

Produce one or more letters.  

Each letter is in a separate @code{letter} environment, whose argument
@var{recipient address} often contains multiple lines separated with a
double backslash@tie{}(@code{\\}).  For example, you might have:

@example
 \begin@{letter@}@{Mr. Joe Smith \\ 
      2345 Princess St. \\ 
      Edinburgh, EH1 1AA@}
   ...
 \end@{letter@}
@end example

The start of the @code{letter} environment resets the page number to 1,
and the footnote number to 1 also.

The @var{sender address} and @var{sender name} are common to all of the
letters, whether there is one or more, so these are best put in the
preamble.  As with the recipient address, often @var{sender address}
contains multiple lines separated by a double
backslash@tie{}(@code{\\}).  @LaTeX{} will put the @var{sender name}
under the closing, after a vertical space for the traditional
hand-written signature; it also can contain multiple lines.

Each @code{letter} environment body begins with a required @code{\opening} command
such as @code{\opening@{Dear Madam or Sir:@}}.  The @var{letter body}
text is ordinary @LaTeX{} so it can contain everything from
enumerated lists to displayed math, except that commands such as
@code{\chapter} that make no sense in a letter are turned off.  Each
@code{letter} environment body typically ends with a @code{\closing}
command such as @code{\closing@{Yours,@}}.

@findex \\ @r{for letters}
Additional material may come after the @code{\closing}.  You can say who
is receiving a copy of the letter with a command like @code{\cc@{the
Boss \\ the Boss's Boss@}}.  There's a similar @code{\encl} command for
a list of enclosures.  And, you can add a postscript with @code{\ps}.

@LaTeX{}'s default is to indent the signature and the @code{\closing}
above it by a length of @code{\longindentation}.  By default this is
@code{0.5\textwidth}. To make them flush left, put
@code{\setlength@{\longindentation@}@{0em@}} in your preamble.

To set a fixed date use something like
@code{\renewcommand@{\today@}@{2015-Oct-12@}}.  If put in your preamble
then it will apply to all the letters.

This example shows only one @code{letter} environment.  The three lines
marked as optional are typically omitted.

@example
\documentclass@{letter@}
\address@{Sender's street \\ Sender's town@}
\signature@{Sender's name \\ Sender's title@}
% optional: \location@{Mailbox 13@}
% optional: \telephone@{(102) 555-0101@}
\begin@{document@}
\begin@{letter@}@{Recipient's name \\ Recipient's address@}
\opening@{Sir:@}
% optional: \thispagestyle@{firstpage@}
I am not interested in entering a business arrangement with you.
\closing@{Your most humble, etc.,@}
\end@{letter@}
\end@{document@}
@end example

These commands are used with the @code{letter} class.

@menu
* \address::                       Sender's return address.
* \cc::                            Carbon copy list.
* \closing::                       Saying goodbye.
* \encl::                          List of enclosed material.
* \location::                      Sender's organizational location.
* \makelabels::                    Make address labels.
* \name::                          Sender's name, for the return address.
* \opening::                       Saying hello.
* \ps::                            Adding a postscript.
* \signature::                     Sender's signature.
@c ?Not user-level? * \stopbreaks and \startbreaks::   Disallow and allow page breaks.
* \telephone::                     Sender's phone number.
@end menu


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

@findex \address

Synopsis: 

@example
\address@{@var{senders address}@}
@end example

Specifies the return address as it appears on the letter and on the
envelope.  Separate multiple lines in @var{senders address} with a
double backslash@tie{}@code{\\}.

Because it can apply to multiple letters this declaration is often put
in the preamble.  However, it can go anywhere, including inside an
individual @code{letter} environment.

This command is optional: without the @code{\address} declaration the
letter is formatted with some blank space on top, for copying onto
pre-printed letterhead paper.  (@xref{Overview}, for details on your
local implementation.)  With the @code{\address} declaration, it is
formatted as a personal letter.

Here is an example.

@example
\address@{Stephen Maturin \\
         The Grapes of the Savoy@}
@end example


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

@findex \cc
@cindex cc list, in letters

Synopsis:

@example
\cc@{@var{first name} \\ 
     ... @}
@end example

Produce a list of names to which copies of the letter were sent.  This
command is optional.  If it appears then typically it comes after
@code{\closing}.  Separate multiple lines with a double
backslash@tie{}@code{\\}, as in:

@example
\cc@{President \\
    Vice President@}
@end example


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

@findex \closing
@cindex letters, ending
@cindex closing letters

Synopsis:

@example
\closing@{@var{text}@}
@end example

Usually at the end of a letter, above the handwritten signature, there
is a @code{\closing} (although this command is optional).  For example,

@example
\closing@{Regards,@}
@end example


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

@findex \encl
@cindex enclosure list

Synopsis:

@example
\encl@{@var{first enclosed object} \\ 
       ... @}
@end example

Produce a list of things included with the letter. This command is
optional; when it is used, it typically is put after @code{\closing}.
Separate multiple lines with a double backslash@tie{}@code{\\}.

@example
\encl@{License \\
       Passport @}
@end example


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

@findex \location

Synopsis:

@example
\location@{@var{text}@}
@end example

The @var{text} appears centered at the bottom of the each page.  It only
appears if the page style is @code{firstpage}.


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

@findex \makelabels

Synopsis:

@example
\makelabels
@end example

Create a sheet of address labels from the recipient addresses, one for
each letter. This sheet will be output before the letters, with the idea
that you can copy it to a sheet of peel-off labels.  This command goes
in the preamble.

Customize the labels by redefining the commands @code{\startlabels},
@code{\mlabel}, and @code{\returnaddress} in the preamble.  The command
@code{\startlabels} sets the width, height, number of columns, etc., of
the page onto which the labels are printed.  The command
@code{\mlabel@{@var{sender address}@}@{@var{recipient address}@}}
produces the two labels (or one, if you choose to ignore the @var{sender
address}). The @var{sender address} is the value returned by the macro
@code{\returnaddress} while @var{recipient address} is the value passed
in the argument to the @code{letter} environment.  By default
@code{\mlabel} ignores the first argument, the @var{sender address}.

@c xxx TODO, align on latex2e-fr.texi, see https://mail.gna.org/public/latexrefman-discuss/2015-10/msg00000.html

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

@findex \name

Synopsis:

@example
\name@{@var{name}@}
@end example

Sender's name, used for printing on the envelope together with the
return address.


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

@findex \opening
@cindex letters, starting

Synopsis:

@example
\opening@{@var{text}@}
@end example

This command is required.  It starts a letter, following the
@code{\begin@{letter@}@{...@}}. The mandatory argument @var{text} is the
text that starts your letter.  For instance:

@example
\opening@{Dear John:@}
@end example


@node \ps
@section @code{\ps}
@findex \ps
@cindex postscript, in letters

Synopsis:

@example 
\ps@{@var{text}@}
@end example

Add a postscript.  This command is optional and usually is used after
@code{\closing}.

@example
\ps@{P.S. After you have read this letter, burn it. Or eat it.@}
@end example


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

Synopsis:

@example 
\signature@{@var{first line} \\
            ... @}
@end example

@findex \signature

The sender's name.  This command is optional, although its inclusion is
usual.

The argument text appears at the end of the letter, after the closing
and after a vertical space for the traditional hand-written
signature. Separate multiple lines with a double
backslash@tie{}@code{\\}.  For example:

@example
\signature@{J Fred Muggs \\
           White House@}
@end example

@LaTeX{}'s default for the vertical space from the @code{\closing} text
down to the @code{\signature} text is @code{6\medskipamount}, which is
six times 0.7@dmn{em}.

This command is usually in the preamble, to apply to all the letters in
the document.  To have it apply to one letter only, put it inside a
@code{letter} environment and before the @code{\closing}.

You can include a graphic in the signature, for instance with
@code{\signature@{\vspace@{-6\medskipamount@}\includegraphics@{sig.png@}\\
My name@}} (this requires writing @code{\usepackage@{graphicx@}} in the
preamble).


@c I think this is not a user-level command; it is used to keep from breaking
@c the page between the closing and the signature
@c @node \stopbreaks and \startbreaks
@c @section @code{\stopbreaks} and @code{\startbreaks}

@c @findex \startbreak
@c @findex \stopbreaks

@c @example 
@c @code{\stopbreaks}
@c text
@c @code{\startbreaks}
@c @end example

@c The @code{\stopbreaks} inhibits page breaking.  The @code{\startbreaks} resumes
@c normal page breaking.
@c
@c
@node \telephone
@section @code{\telephone}

@findex \telephone

Synopsis:

@example
\telephone@{@var{number}@}
@end example

The sender's telephone number.  This is typically in the preamble, where
it applies to all letters.  This only appears if the @code{firstpage}
pagestyle is selected.  If so, it appears on the lower right of the
page.


@node Terminal input/output
@chapter Terminal input/output

@cindex input/output, to terminal
@cindex terminal input/output

@menu
* \typein::             Read text from the terminal.
* \typeout::            Write text to the terminal.
@end menu


@node \typein
@section @code{\typein[@var{cmd}]@{@var{msg}@}}

@findex \typein

Synopsis:

@example
\typein[\@var{cmd}]@{@var{msg}@}
@end example

@code{\typein} prints @var{msg} on the terminal and causes @LaTeX{} to
stop and wait for you to type a line of input, ending with return.  If
the optional @code{\@var{cmd}} argument is omitted, the typed input is
processed as if it had been included in the input file in place of the
@code{\typein} command.  If the @code{\@var{cmd}} argument is present, it
must be a command name.  This command name is then defined or
redefined to be the typed input.


@node \typeout
@section @code{\typeout@{@var{msg}@}}

@findex \typeout

Synopsis:

@example
\typeout@{@var{msg}@}
@end example

Prints @code{msg} on the terminal and in the @code{log} file.
Commands in @code{msg} that are defined with @code{\newcommand} or
@code{\renewcommand} (among others) are replaced by their definitions
before being printed.

@LaTeX{}'s usual rules for treating multiple spaces as a single space
and ignoring spaces after a command name apply to @code{msg}.  A
@code{\space} command in @code{msg} causes a single space to be
printed, independent of surrounding spaces.  A @code{^^J} in
@code{msg} prints a newline.


@node Command line
@chapter Command line

@cindex command line

@findex .tex, @r{default extension}
The input file specification indicates the file to be formatted;
@TeX{} uses @file{.tex} as a default file extension.  If you omit the
input file entirely, @TeX{} accepts input from the terminal.  You can
also specify arbitrary @LaTeX{} input by starting with a backslash.
For example, this processes @file{foo.tex} without pausing after every
error:

@example
latex '\nonstopmode\input foo.tex'
@end example

@findex --help @r{command-line option}
With many, but not all, implementations, command-line options can also
be specified in the usual Unix way, starting with @samp{-} or
@samp{--}.  For a list of those options, try @samp{latex --help}.

@cindex @samp{*} prompt
@cindex prompt, @samp{*}
@findex \stop
If @LaTeX{} stops in the middle of the document and gives you a
@samp{*} prompt, it is waiting for input.  You can type @code{\stop}
(and return) and it will prematurely end the document.

@xref{@TeX{} engines}, for other system commands invoking @LaTeX{}.


@node Document templates
@appendix Document templates

@cindex document templates
@cindex templates, document

Although not reference material, perhaps these document templates will
be useful.  Additional template resources are listed at
@url{http://tug.org/interest.html#latextemplates}.

@menu
* beamer template::
* book template::
* tugboat template::
@end menu


@node beamer template
@section @code{beamer} template

@cindex @code{beamer} template and class
@cindex template, @code{beamer}

The @code{beamer} class creates presentation slides.  It has a vast
array of features, but here is a basic template:

@verbatim
\documentclass{beamer}

\title{Beamer Class template}
\author{Alex Author}
\date{July 31, 2007}

\begin{document}

\maketitle

% without [fragile], any {verbatim} code gets mysterious errors.
\begin{frame}[fragile]
 \frametitle{First Slide}

\begin{verbatim}
  This is \verbatim!
\end{verbatim}

\end{frame}

\end{document}
@end verbatim

One web resource for this:
@url{http://robjhyndman.com/hyndsight/beamer/}.


@node book template
@section @code{book} template

@cindex template, @code{book}

@verbatim
\documentclass{book}
\title{Book Class Template}
\author{Alex Author}

\begin{document}
\maketitle

\chapter{First}
Some text.

\chapter{Second}
Some other text.

\section{A subtopic}
The end.
\end{document}
@end verbatim


@node tugboat template
@section @code{tugboat} template

@cindex template, TUGboat
@cindex TUGboat template
@cindex @code{ltugboat} class

@cite{TUGboat} is the journal of the @TeX{} Users Group,
@url{http://tug.org/TUGboat}.

@verbatim
\documentclass{ltugboat}

\usepackage{graphicx}
\usepackage{ifpdf}
\ifpdf
\usepackage[breaklinks,hidelinks]{hyperref}
\else
\usepackage{url}
\fi

%%% Start of metadata %%%

\title{Example \TUB\ article}

% repeat info for each author.
\author{First Last}
\address{Street Address \\ Town, Postal \\ Country}
\netaddress{user (at) example dot org}
\personalURL{http://example.org/~user/}

%%% End of metadata %%%

\begin{document}

\maketitle

\begin{abstract}
This is an example article for \TUB{}.
Please write an abstract.
\end{abstract}

\section{Introduction}

This is an example article for \TUB, linked from
\url{http://tug.org/TUGboat/location.html}.

We recommend the \texttt{graphicx} package for image inclusions, and the
\texttt{hyperref} package if active urls are desired (in the \acro{PDF}
output).  Nowadays \TUB\ is produced using \acro{PDF} files exclusively.

The \texttt{ltugboat} class provides these abbreviations (and many more):
% verbatim blocks are often better in \small
\begin{verbatim}[\small]
\AllTeX \AMS \AmS \AmSLaTeX \AmSTeX \aw \AW
\BibTeX \CTAN \DTD \HTML
\ISBN \ISSN \LaTeXe
\mf \MFB
\plain \POBox \PS
\SGML \TANGLE \TB \TP
\TUB \TUG \tug
\UNIX \XeT \WEB \WEAVE

\, \bull \Dash \dash \hyph

\acro{FRED} -> {\small[er] fred}  % please use!
\cs{fred}   -> \fred
\meta{fred} -> <fred>
\nth{n}     -> 1st, 2nd, ...
\sfrac{3/4} -> 3/4
\booktitle{Book of Fred}
\end{verbatim}

For references to other \TUB\ issue, please use the format
\textsl{volno:issno}, e.g., ``\TUB\ 32:1'' for our \nth{100} issue.

This file is just a template.  The \TUB\ style documentation is the
\texttt{ltubguid} document at \url{http://ctan.org/pkg/tugboat}.  (For
\CTAN\ references, where sensible we recommend that form of url, using
\texttt{/pkg/}; or, if you need to refer to a specific file location,
\texttt{http://mirror.ctan.org/\textsl{path}}.)

Email \verb|tugboat@tug.org| if problems or questions.

\bibliographystyle{plain}  % we recommend the plain bibliography style
\nocite{book-minimal}      % just making the bibliography non-empty
\bibliography{xampl}       % xampl.bib comes with BibTeX

\makesignature
\end{document}
@end verbatim


@node Concept Index
@unnumbered Concept Index

@printindex cp

@c The name of the `Command Index' node must NOT be altered for ltx-help.el.
@node Command Index
@unnumbered Command Index

@printindex fn

@bye

\def\DeclareTextCommand{\foo}{T1}
%    then |\foo| is defined to be |\T1-cmd \foo \T1\foo|,
%    %    where |\T1\foo| is \emph{one} control sequence, not two!
\newcommand

\def\ProvideTextCommand -- same with \providecommand
\@onlypreamble\DeclareTextCommand
\@onlypreamble\DeclareTextSymbol
\gdef\TextSymbolUnavailable#1{%
\@onlypreamble\def\DeclareTextCommandDefault#1{%
\def\ProvideTextCommandDefault#1{%
\def\DeclareTextAccent#1#2#3{%
\def\DeclareTextCompositeCommand#1#2#3#4{%
\@onlypreamble\def\DeclareTextComposite#1#2#3#4{%
\def\UseTextAccent#1#2#3{%
\def\UseTextSymbol#1#2{%
\@onlypreamble\DeclareTextSymbolDefault@item
\@onlypreamble\DeclareTextAccentDefault@item
\def\UndeclareTextCommand#1#2{%

@c Local Variables:
@c ispell-dictionary: "english"
@c coding: latin-1-unix
@c End:
