\chapter{First steps}
\section{A brief history}
\LaTeX\ can be thought of as the fusion of two
developments in computing software. One of these developments was
\TeX; the other was \Scribe\index{scribe@\protect{\Scribe}}. Both are embedded in
the academic world. Both came to fruition in the latter part of the
70's, and as such, preceded the introduction of personal
computers. They also parallel the rise of large scale database
systems, and the demise of traditional hand-set type.

\subsection{\TeX}
\TeX\ itself was developed as a typesetting tool by
Donald Knuth\index{Knuth} of Stanford University~\cite{DEK84}. Knuth wrote
the first version of \TeX\index{tex@\protect{\TeX}} in the late 1970s
\cite{DEK79}, primarily as a way of controlling the printed quality of his
multi-volume work \textsl{The Art of Computer Programming}~\cite{DEK68}. 

To some extent, and more particularly with the early
versions, \TeX\ tended to place some emphasis on the
arrangement of the marks on the paper. After all, Knuth
finishes~\cite{DEK84} with the exhortation: `\textsc{Go
Forth} {and create masterpieces of the publishing art!}'.  He was
clearly thinking in terms of marks on paper. Because of this
attention to this relatively low level of detail, \TeX\ is sometimes
described as a \emph{procedural} or \emph{typographic markup}\index{markup}
system.

\subsection{\Scribe}
\Scribe\index{scribe@\protect{\Scribe}} was
written by Brian Reid at Carnegie-Mellon~\cite{BR80}, and
described in his thesis in 1980. In essence, \Scribe\ ignored the
content of the document, concentrating on the
relationship of the parts: in a sense it imposed, or
revealed, the implicit inter-relationships present.
We may be prepared to acknowledge that a document is composed of
(say)
\begin{itemize}
\item front matter
\item main text
\item annexed (or back) matter 
\end{itemize}
and within each of these major divisions, we can identify
subdivisions. The front matter might comprise
\begin{itemize}
\item title page
\item author's dedication
\item table of contents
\item list of figures
\item foreword
\item preface
\item acknowledgements
\end{itemize}
and so on. Some of these elements may be optional. This
presents structure as very hierarchical, but it is
possible to construct arrangements which are not so
fiercely arranged, and share features with other, less
formal, types of organisation. 

One of the major points to make is that \Scribe\ was a
system of \emph{descriptive} or \emph{logical markup}\index{markup}: it
described the structure of the document. It made no comment about the
arrangement of the words on the page. In fact, there need
be no `page', in the sense of `paper' page. Changing the
characteristics of the `carrier medium' changed nothing
about the document structure. While it is possible to
disagree with extreme versions of this viewpoint \cite{MC96}, it
did offer a powerful and attractive way to separate documents
from the worries of formatting.

\subsection{\LaTeX}
Leslie Lamport~\cite{LL85} took the ideas of \Scribe\ and the
typesetting capabilities of \TeX\ and fused them into
\LaTeX, a piece of software where an author could include
an account of the structure\index{structure} together with the content --
the words. Lamport sought to devise a system where the
author need know nothing about the details of typesetting
-- justification, choice of typeface, page breaking,
ligatures, and so on. Merely by saying that the document
was a `book', or a `report', the text would be formatted
appropriately.


In contemporary jargon, \TeX\ is described as the \emph{formatting} or \emph{typesetting
engine} whose presence need never be revealed. The author
concentrates on the content, merely guiding the structure gently by
noting features like sections, subsections, figures, etc. To this
Lamport added or adapted tools to sweep up tables of contents, lists of
figures, cross referencing, bibliographic control and
indexing. Perhaps these \emph{value added} tools\index{tools} are the
features which still give \LaTeX\ the edge over almost any
other software of this type. 

That and the fact that it is
available, if not freely, certainly very cheaply. A great
deal of the work on \TeX\ and \LaTeX\ has been done
through the public domain. This does not mean it was done
for free: a great deal of money was spent, one way or
another, in perfecting these tools. Fortunately for the
rest of us, a lot of
it was `public' (i.e.~taxpayers') money, rather than `commercial'
money. Even the commercial versions of \TeX\ and \LaTeX\
are very cheap when compared to `comparable' commercial
alternatives. 

\LaTeX\ absorbed all \TeX's mathematical capability.
Since \LaTeX\ is written in \TeX\ (which itself has some
pretensions to being a programming language), anything
that is possible in \TeX\ can also be done in \LaTeX, so
we have lost no functionality. This is really only theoretically
true, since, as we may see, \TeX\ itself has some memory
limitations: once the \LaTeX\ functionality is loaded, there is
limited space left for other things. But this is an architectural
problem rather than a conceptual one.

One of Lamport's advantages was that he was able to work
with Knuth, as Knuth was developing the `final' version
of \TeX. Certain requirements which came to light with
the development of the early versions of \LaTeX\ were
incorporated into \TeX82, the version of \TeX\ which we all used
until Knuth \cite{DEK89} made some relatively small changes in 1989; this latter
change was a
relatively straightforward and painless upgrade which may even
have gone unnoticed by some.  Lamport is
quoted somewhere as saying that he could not have achieved what he
had done without the active cooperation of Knuth. This is not to
minimise Lamport's achievement, since
\LaTeX\ is a wholly remarkable piece of software. It has
defects, but to a large extent these turn out not to be
too limiting. Some of its problems are really problems
inherent in \TeX. But more of that later (perhaps).

\subsection{\LaTeXe}\index{latex!latex2e@\protect{\LaTeXe}}
Some other changes have to be documented. For a long period,
\LaTeX\ was also known as
\LaTeX\,2.09\index{latex!latex2.09@\protect{\LaTeX}\,2.09}. This actually
covered an incremental refinement where bug fixes were gradually incorporated
without changing the version number and was leading to uncertainty of what was
the `current' version of \LaTeX, and some divergence of what it actually
constituted. This was not altogether satisfactory. By 1990 there was the
beginning of a proposal to change \LaTeX\ substantially \cite{FM90}, for a
variety of  sound reasons. Ultimately this gelled into a proposal for a new
version  to be called \LaTeX3\index{latex!latex3@\protect{\LaTeX}\,3}
\cite{FMCR92}. In the meantime, to hold us until the new version is ready, a
consolidation, \LaTeXe\ was publicly released in 1994. This is the
version of \LaTeX\ which constitutes the core of this discussion. From
time to time it will be necessary to recap some of the history which
brought us to \LaTeXe, but by and large the discussion is directed
at \LaTeXe. When some peculiarity of \LaTeXe\ is mentioned it will be
referred to as such, but most of the time, \LaTeX\ and \LaTeXe\
will mean the same thing. 

When will \LaTeX3 be released? Or rather, will your investment in
learning \LaTeX\ be lost when \LaTeX3 appears? I hope not, not
least since my investment will be lost too. It will take some time
before \LaTeX3 appears, and even when it does, the concepts will
likely stay much the same, although there may be detail changes \cite{DCCRFM98}. 
Furthermore, it is likely that there may be some sort of
compatibility mode, where existing (or \emph{legacy}) documents written in \LaTeX\
will be capable of being processed with \LaTeX3. Nothing should be
wasted. The investment is just too vast to risk.

\subsection{A proviso}
One possible disadvantage of the \LaTeX\slash\Scribe\
approach is that it requires that you have a notion of
just what it is you are trying to do: some people write
electronic or digital documents in a very haphazard, piecemeal
fashion, jumping around the document, and basically
losing track of things. If this is the way you work, and
you resent the rigour of structure, seeing it as a
straight-jacket rather than scaffolding, you may be
unhappy with \LaTeX. A little bit of discipline may help
to refine your ideas, and, in the longer term, achieve
more.


It is certainly true that you will not learn all there is
to know about \LaTeX\ from this brief account. On the other hand,
with its aid, you may learn enough to be able to
produce (apparently) complex documents, and without too much trouble.
Systems which are learned quickly sometimes lack stamina.
To some extent \LaTeX\ can be approached in an
`intuitive' way, but no-one is likely to try to claim
that it is especially `user-friendly', at least, not
until you are properly introduced.


\section{A note on pronunciation}
Some people get very worked up about the pronunciation
of \TeX\ and \LaTeX. Knuth says of `\TeX'\index{tex@\protect{\TeX}}
\begin{quote}
``Insiders pronounce the $\chi$ of \TeX\ as the Greek chi, not as a
`x', so that \TeX\ rhymes with the word blecchhh. It's the `ch'
sound in Scottish words like {\em loch\/} or German words like {\em
ach}; it's a Spanish `j' and a Russian `kh'.''
\end{quote}
Unfortunately, few of the English-speaking world are equipped to
pronounce \emph{loch}, and the German-speaking world has (at
least) two pronunciations of \emph{ach} -- the less obvious,
southern German form, is like \emph{ash} or perhaps \emph{asch}. In
the end, the majority of English-speakers seem to end up with
\emph{tecks} or \emph{teck}.

Lamport sagely notes: 
\begin{quote} 
``\dots pronunciation is best determined by usage, not fiat.
\TeX\ is usually pronounced \emph{teck}, making \emph{lah}-teck,
lah-\emph{teck}, and \emph{lay}-teck the logical choices; but
language is not always logical, so \emph{lay}-tecks is also
possible.''
\end{quote}
About the only possibility Lamport does not cover is \emph{L-A-teck}, so
perhaps we can conclude that that is not a recommended
pronunciation.

Of course, Knuth's description, as given here, begs the question a
little, since it does not say where the Greek chi comes from.
Knuth's original notion, in naming the software \TeX, was to use the
roman form of $\tau\epsilon\chi$, which is the beginning of the
Greek word transliterated as \emph{tekhn\=e}, which we use in words
like
\emph{technology}. To the Greeks this encompassed art \emph{and}
technology. A better rendition into contemporary english would
probably be something like \emph{craftsmanship}. An exposition of
\emph{tekhn\=e} might be the Parthenon in Athens, or even any piece
of work which was the responsibility of Isambard Kingdom Brunel.

But, however we pronounce `\TeX' and `\LaTeX', we will always
recognize the logos, which are so difficult to produce in most
every other system. If you do have to write \TeX\ or \LaTeX\ in a
system where you cannot drop the `E' or raise the `A', write them
like `TeX' and `LaTeX'.  

\begin{question}
What would you say were the structural elements of a memo? or a
letter? What are the bits which are always present?
\end{question}
\begin{question}
This question cannot be answered immediately, but it may be
revealing if you keep it in your mind as you read through the book.
Ponder on the extent to which developments in software are  related
to available hardware. Try to imagine the sort of hardware and
operating systems which were available as Knuth was developing \TeX.
Contrast that with the hardware and operating systems which have led
to the development of \textsl{wysiwyg} (what you see is what you
get) software. What might Knuth and Lamport have done if they were
developing \TeX\slash\LaTeX\ today? 
\end{question}
\begin{question}
Take a word processing or document formatting system with which you
are familiar -- \texttt{nroff}, Runoff, \textsl{Pagemaker},
WordPerfect, Word, FrameMaker, Interleaf, Quark Xpress, lout,
\textsc{html}, paper and pencil, typewriter, etc., and note down what
seem to be their \emph{descriptive} and \emph{procedural} elements.
Which bits are concerned only with positioning of characters on the
page, and which bits describe items independently of their form? There
may even be a third category where the positioning and the `content' are
combined.
\end{question}

\section{Let's try it}
Since \LaTeX\ was developed for documentation, it is a good idea to
start with a fairly straightforward document and see
what it is we have to do in order to translate it onto
the page. We will assume that `marks on paper' are the
goal. The `paperless office' still seems as far away as ever,
despite efforts from most computer manufacturers, Xerox {\sc parc},
and the damage being done to the forests of the world.  

We will begin with the output: the end product of the document
preparation process. This end product, Figure~\ref{ishmael}, 
is not spectacular, but it does have some interesting
features, most of which we probably take for granted.
\begin{figure*}
\centerline{\fbox{\includegraphics{ishmael}}}
\caption{}\label{ishmael}
\end{figure*}
If we examine the input file, we will see that the text is enclosed
between the instructions in the following manner:\index{documentclass@\texttt{documentclass}}

\begin{small}
\begin{verbatim}
\documentclass{book}
\begin{document}
\chapter{Example formatted file}
I stuffed a shirt or two into my old carpet-bag,
tucked it under my arm, and started for Cape Horn
and the Pacific. Quitting the good city of old
Manhatto, I duly arrived in New Bedford.  It was
on a Saturday night in December. Much was I
disappointed upon learning that the little packet
for Nantucket had already sailed, and that no way
of reaching that place would offer, till the
following Monday.

As most young candidates for the pains and
penalties of whaling stop at this same New
Bedford, thence to embark on their voyage, it may
as well be related that I, for one, had no idea of
so doing. For my mind was made up to sail in no
other than a Nantucket craft, because there was a
fine boisterous something about everything
connected with that famous old island, which
amazingly pleased me. Besides though New Bedford
has of late been gradually monopolizing the
business of whaling, and though in this matter
poor old Nantucket is now much behind her, yet
Nantucket was her great original --- the Tyre of
this Carthage; --- the place where the first dead
American whale was stranded. Where else but from
Nantucket did those aboriginal whalemen, the
Red-Men, first sally out in canoes to give chase
to the Leviathan?  And where but from Nantucket,
too, did that first adventurous little sloop put
forth, partly laden with imported cobblestones ---
so goes the story --- to throw at the whales, in
order to discover when they were nigh enough to
risk a harpoon from the bowsprit?

Now having a night, a day, and still another night
following before me in New Bedford, ere I could
embark for my destined port, it became a matter of
concernment where I was to eat and sleep
meanwhile. It was a very dubious-looking, nay, a
very dark and dismal night, bitingly cold and
cheerless. I knew no-one in the place.  With
anxious grapnels I had sounded my pocket, and only
brought up a few pieces of silver, --- ``So,
wherever you go, Ishmael,'' said I to myself, as I
stood in the middle of a dreary street shouldering
my bag, and comparing the gloom towards the north
with the darkness towards the south --- ``wherever
in your wisdom you may conclude to lodge for the
night, my dear Ishmael, be sure to inquire the
price, and don't be too particular.''
\end{document}
\end{verbatim}
\end{small}

\LaTeX\ has handled all the details of page size,
line-breaks, page-breaks (take my word on that one), 
hyphenation, ligaturing, paragraph
indentation, justification, the white space between lines, 
 and so on. These are all implied through the adoption of
the `book' document style.

Another feature which may have appeared transparently is the text's
division into paragraphs. If you leave a blank line,
\LaTeX\ will implicitly assume that this represents a paragraph break. 
And by default it will leave 
indentation at the beginning of the paragraph.

\section{Elementary typography}
What are ligatures\index{ligature}? In many ways they are left-overs from the
days of scribes. They are recognized `running together' of letters, to form a new symbol. The most
common examples, found in many typefaces are: 
\begin{center}
\begin{tabular}{r@{\quad$\to$\quad}l}
f{\,}f&ff\\
f{\,}i&fi\\
f{\,}l&fl\\
f{\,}f{\,}i&ffi\\
f{\,}f{\,}l&ffl
\end{tabular}
\end{center}
This is not simply a `very close' duo or trio of individual letters, but a completely new symbol.

This is by no means a universal transformation. It is bound by
typeface, by culture, and by time. Gutenberg's original 42 line
Bible, printed in about 1455, has at least 50 different ligatures. He
was trying to emulate the work of scribes. They had evolved all
sorts of shortenings which he strove to adopt. By the 19th century,
English had standardized on the 5 or so above, but  `ct' and `st' ligatures
persisted at least up to the middle of this century, although in rather specialist
typefaces. Although ligatures are more common in `serifed' typefaces, some
sans serif faces do have ligatures. Equally some fairly traditional
serifed faces have abandoned them. Stanley Morison, who is credited
with the design of the `Times' typeface, may well be rotating in his
grave now that \textsl{The Times} has dispensed with ligatures.


\LaTeX\ takes care of ligatures without even thinking about it too
deeply. It also takes care of `kerning'\index{kern}. Kerning is a much more
recent introduction, and occurs where letters overlap, but do not
touch. This is much more noticeable in capital letters: OXO or WAVE
ought to be good examples, where the horizontal extent of each
character overlaps with that of the next character. Again,
kerning is not supported in all fonts. In particular, you would
probably not want kerning in a font which was supposed to look like
typewriter characters. Kerning relates to the moving together of
characters to make the letter spacing more pleasing: it might be
better to describe this as `less displeasing'. We may notice when a
book is difficult to read because of the typography: we seldom
notice when it is easy to read. This is as it should be. A warning:
exposure to \TeX\ and \LaTeX\ can affect your enjoyment of the
printed word. You start to look at the typography much more closely.
It can destroy some books entirely.

You may perhaps notice some other things which are done entirely
automatically, and which tend to distinguish `typesetting' systems
from `desktop publishing' or word processing systems. The first
distinguishing feature  is the three different sorts of horizontal
rules or dashes, used in  text (although in Figure~\ref{ishmael} 
only two of them are used):

In fact, dashes\index{dash} come in lots of forms. Formally we identify
the following: the hyphen, the en-dash\index{en-dash}, and the
em-dash\index{em-dash} (and the minus\index{minus} sign too, but we'll look at
that later): see Table~\ref{dashit}. In most typestyles these will be different characters. A
hyphen\index{hyphen} is fairly obvious, and is conveyed to \LaTeX\  as a
\texttt{-} symbol. An en-dash is a longer symbol (about the length of an N in the
current font), and is therefore conveyed to \LaTeX\  as \verb|--|; an en-dash is
usually employed to convey the idea of a range, for example
1--10. Occasionally too, an en-dash is used when two names are joined,
like Runge--Kutta or Russell--Hertzsprung, although they are often just
hyphenated. Thirdly, the em-dash is even longer (related to the capital
M), and is given to
\LaTeX\  as \verb|---|. The em-dash is punctuation in text. (The minus is a
mathematical symbol which has to be given in maths  -- to be
covered later -- as \verb|$-$|.) 
\begin{table*}
\begin{center}
\begin{tabular}{lccl}
\hline
`correct name' & \LaTeX\ form & typeset form & example\\
\hline
hyphen    & \verb|-|     &     -   &  hy-phen\\
en-dash   & \verb|--|    &    --   &  1--7   \\
em-dash   & \verb|---|   & ---     & Knuth---the archi\TeX t\\
minus     & \verb| - |   &   $-$   & $x-y$ \\
\hline 
\end{tabular}
\caption{Length and meaning of horizontal lines\label{dashit}}
\end{center}
\end{table*}

Another feature is treated by \LaTeX\ as a sort of
ligature\index{ligature}.  Quotation marks\index{quotation mark}
(i.e.\ double inverted commas) come in open and close varieties in
many fonts. \LaTeX\ employs the quote (also known as
\textit{apostrophe} and \textit{prime}) and grave. On one of my keyboards
`quote' is on the right of the keyboard, just beside the
\verb|return| key). The left quote, or {\it grave} is at the top
left of the keyboard, beyond the numerical characters). Unfortunately, 
the `extra' characters on a keyboard do not
have standardized positions, and the location on your keyboard may
differ. Clearly, this provides you with only a single inverted left or
right comma at a time.  \LaTeX\ `ligatures' a pair of inverted
commas, whether they be grave or quote, to form a single `double'
quote mark. Thus, to form a double open quote mark on output (the `66' form)
 -- `` -- type a pair of graves -- \verb|``|, and to form the corresponding 
(`99') close
double quotes -- '' -- type a pair of quotes -- \verb|''|. The double quote
symbol on your keyboard -- \verb|"| -- should not be used.



\section{In the beginning}
The content of \emph{every} document we write with \LaTeX\ has a beginning and
end  delimited by the \verb|\begin{document}|\index{begin@\texttt{begin}} --
\verb|\end{document}|\index{end@\texttt{end}}\index{document@\texttt{document}}
pairing. Note that this is the beginning and end of textual content of the document. It is not the
beginning and end of the file of information. While it seems that there is little point in placing
anything after the \verb|\end{document}| statement, since it will never by
seen by \LaTeX, it is somewhere to keep notes, odd ideas and even
pieces of text you plan to use in the future.

This is described as a `document' \emph{environment}. The notion of
an enclosed environment, with a matching \verb+\begin+ and 
\verb+\end+ pair is fairly fundamental to \LaTeX. 

 The very beginning of the file of information has a
\verb|\documentclass| statement. This statement will be modified by
additional instructions which will determine many of the layout
alternatives which will be adopted; it also has some bearing on the
sorts of structures which are available.
\LaTeX\ has a small number of fixed document 
\emph{classes}\index{class} associated with it.

\section{Classes of style, flair and panache}
The basic \LaTeX\ document classes\index{document classes} are \texttt{book},
\texttt{report}, \texttt{article}, \texttt{letter}, \texttt{slides},
\texttt{proc} and \texttt{ltxdoc}. The first four of these
were the original `styles' released with \LaTeX\ and  documented (to
some extent) in the original manual \cite{LL85}. The remainder were
introduced with \LaTeXe, when the concept of `document class'
was also introduced, and separated carefully (though not wholly
convincingly) from `style'\index{style} (see also~\cite{LL94}).  
In general the names are descriptive,
meaningful and obvious. For those already familiar with \LaTeX\ the class
\texttt{slides} replaces \SliTeX, while \texttt{proc} is intended
to handle a conference proceedings. The last, \texttt{ltxdoc} is
an indirect product of the documentation effort related to
\LaTeXe\ and \LaTeX3, and is intended to assist in the
documentation of classes and styles. It will not be examined here.

There are other classes around, many of which are referred to and
described in the \textsl{\LaTeX{} Companion} \cite{MGFMAS94}. In
theory, these classes and styles should be documented in what Lamport refers to as
the \textsl{Local Guide}. He had the notion that every installation
would have a locally produced \textsl{Guide} which would contain
useful information on the availability of fonts, classes, styles, support
software, and so on.  \textsl{Guides} are usually conspicuous by their
absence. The \textsl{Companion} is an admirable substitute.

The implications of each style are sometimes hard to grasp. Just how
does \texttt{report} differ from \texttt{article}? To some extent
this is to misunderstand the function of the classes and the model
of \emph{declarative markup}\index{markup} which was outlined earlier. Lamport
worked with a number of document designers to develop the
classes\slash styles. And he made it a non-trivial job to `tweak' the
classes\slash styles to adapt them. In other words, he felt (very
strongly) that you, as the user, should get on with what you were good
at, namely writing, and let \LaTeX\ get on with what it was good at,
namely formatting. To be fair, \LaTeXe\ does simplify some modes
of modification. Everybody wants to tweak. And not everybody
enjoys the layouts adopted by Lamport. They certainly come out of a
particular typographic tradition, one which is not universal. It is
one possible comment that the original
\LaTeX\ book does not use the \texttt{book} layout available with
\LaTeX.

To use a particular class, we say\index{documentclass@\texttt{documentclass}}
\begin{verbatim}
\documentclass{report}
\end{verbatim}
or whichever of the classes we wish to choose. In addition, there are
\emph{options}\index{options}, which modify the fundamental class. For example,
there are \texttt{11pt} and \texttt{12pt} options which allow us to
change the basic size of the font used in the main body of the text. By default, \LaTeX\ uses a 10
point font for its `body text'. \emph{Options} precede the
\emph{class}, and are enclosed in square brackets:
\begin{verbatim}
\documentclass[11pt]{report}
\end{verbatim}



\begin{question}
  The example in Figure~\ref{ishmael} was created using the
  \texttt{book} class (since it is really a chapter from a book). To
  get some crude notion of the effects of changing styles (and
  options), you could edit the \verb|\documentclass| statement to
  create \texttt{article}s or \texttt{report}s at 10, 11 or 12 point.
\end{question}

\begin{question}
What other document classes do you require? 
\end{question}

Although there are few document classes, there are far more options.
There are also lots of `packages'\index{package} which allow us to change some
aspect of the default presentation and features of \LaTeX. Changing
an option or package is far easier than tackling a class. Later we
may look at the modifying or creating packages to alter the default
behaviour of \LaTeX. 

Clearly the options \texttt{10pt}, \texttt{11pt} and \texttt{12pt} are mutually
exclusive. A document may have only one basic type size.
But there are other options which affect some other aspect of the
presentation. For example, \texttt{twoside} formats the output
for printing on both sides of the page (`duplex' printing). Of
course this does not mean they will come out of the   printer
printed on both sides. It simply affects the physical position of the
mass of text on odd and even pages, so that when they are used as
masters (in a photocopier, for example), the text will fall in a
position which ensures that there is no `show through': that is, you cannot see the 
other page's text as a `shadow' through the paper, since it is obscured by the text on the page you
are reading. Such subtle niceties are the traditional concern of printers. Another option is
\texttt{twocolumn}, which produces two-column output. When we specify
several options, they are separated by  commas:
\begin{verbatim}
\documentclass[twocolumn,11pt,twoside]{report}
\end{verbatim}

\begin{table*}
\begin{minipage}{.5\textwidth}
\begin{center}
\begin{tabular}{|ll|}
\hline
\verb+\documentclass+&principal \texttt{options}\\
\hline
\texttt{book} & twocolumn, 10pt, 11pt, 12pt, twoside\\
\texttt{report} & twocolumn, 10pt, 11pt, 12pt, twoside\\
\texttt{article} & twocolumn, 10pt, 11pt, 12pt, twoside\\
\texttt{letter} & 10pt, 11pt, 12pt\\
\texttt{slide} &\\
\texttt{proc} & twocolumn, 10pt, 11pt, 12pt, twoside\\
\texttt{ltxdoc} & twocolumn, 10pt, 11pt, 12pt, twoside\\
\hline
\end{tabular}
\caption{Some of the default range of classes and their
options\label{range}}
\end{center}
\end{minipage}
\begin{minipage}{.5\textwidth}
\begin{center}
\begin{tabular}{|ll|}
\hline
size options&paper size\\
\hline
\texttt{a4paper}&$210\,\textrm{mm}\times297\,\textrm{mm}$\\
\texttt{a5paper}&$148\,\textrm{mm}\times210\,\textrm{mm}$\\ 
\texttt{b5paper}&$176\,\textrm{mm}\times250\,\textrm{mm}$\\
\hline
\texttt{letterpaper}&$8.5\,\textrm{in}\times11\,\textrm{in}$\\
\texttt{legalpaper}&$8.5\,\textrm{in}\times14\,\textrm{in}$\\
\texttt{executivepaper}&$7.25\,\textrm{in}\times10.5\,\textrm{in}$\\
\hline
\end{tabular}
\caption{The  range of page size options\label{size}\index{size}}
\end{center}
\end{minipage}
\end{table*}


\begin{question}
Try a few options.  Does \texttt{twoside} work correctly
on your printer? Be bold.
\end{question}

There are also a set of built in page sizes, Table~\ref{size}, which
do two things: they set the height and width of the text itself, and
they also position where the text will be placed on the page.
Obviously \LaTeX\ cannot know what page size you will ultimately use,
and selecting \texttt{a4paper} will not guarantee that the output
device, perhaps a laser printer, is actually loaded with the correct
size of paper. If you do not use any of these size options, the
default is \texttt{letterpaper}, a rather distressing result outside
the US. If you were using some other size of paper (perhaps for a
book), it would be necessary to set the width and height of the text
through some other means. This method is likely to be inappropriate.
It is also possible to add another option to these,
\texttt{landscape}, which swaps the height and width to give a
`landscape' orientation rather than the more normal `portrait'.

\section{More information}
Part of the structure of a document will be the `front' matter:
things like the title, the author, and so on. \LaTeX\ allows you to
include this information too. We can write something like
\begin{verbatim}
\title{The Carpet-Bag}
\author{Herman Melville}
\date{1851}
\end{verbatim}
By itself, this does nothing. Until we say \verb|\maketitle|\index{title}, this
information does not appear on the page. Since we would expect a
title to appear at the beginning of a document, the \verb|\title|,
\verb|\author| and \verb|\date| should normally appear before we
try to write out the title. The `best' place for the information is
therefore between the \verb|\documentclass| specification and the
\verb|\begin{document}| statement. From time to time this location will
be described as the document \emph{preamble}. But to be truthful, it can go
anywhere. If you do not specify a \verb|\date|, \LaTeX\ will use the
current one (which happens to be \today). In order to omit the date entirely, you could
type \verb+\date{}+. The empty braces are necessary: \verb+\date+
by itself would not give you an acceptable result.

\begin{verbatim}
\documentclass[twocolumn,11pt]{book}
\title{The Carpet-Bag}
\author{Herman Melville}
\date{1851}
\begin{document}
\maketitle
.
.
\end{document}
\end{verbatim}

\begin{question}
Go ahead, do it. Of course you do not have to use \texttt{twocolumn} or
the \texttt{book} document class.
\end{question}

\section{Some back-tracking}
All along we have ignored the presence of some key characters. I
have presented instructions like \verb|\documentclass|\index{backslash} and
\verb|\begin| without much fanfare. The backslash character,
`\verb|\|', is of major importance. All \LaTeX\  instructions are
introduced by such a character. In a sense, it is the
\TeX\slash\LaTeX\ `escape character'. Whatever follows a \verb|\| is
treated in a special way, and will not appear on the page as
such. Obviously there are ways of making backslashes appear on the
page, since this document was produced through \LaTeX. Note too
that \LaTeX\ is case-sensitive\index{case
sensitive}.
\verb|\DocumentClass| will not be understood.  In very general terms, the majority of the
instructions you supply specifically for \LaTeX\ will be in lower
case. Only a  few instructions use upper case characters. 

A \LaTeX\ instruction\index{command}\index{instruction} may  be
constructed in \emph{only} one of two ways. The first\label{commands}, most flexible way,
which we have used already, is by a backslash followed by an arbitrary number of
alphabetic characters. Thus we might expect to see the following as
legal \LaTeX\ instructions: 
\begin{center}
\begin{tabular}{lll}
\verb|\documentclass|&\verb|\raggedbottom|&\verb|\section|\\
\verb|\maketitle|&\verb|\vspace|&\verb|\hspace|\\
\verb|\kill|&\verb|\sloppy|&\verb|\newpage|\\
\verb|\framebox|&\verb|\line|&\verb|\circle|
\end{tabular}
\end{center}
Each one of these is a legitimate instruction which already exists in
\LaTeX. The alternative form is a backslash followed by a
\emph{single non-alphabetic} character. Thus we might expect to see
the following:
\begin{center}
\begin{tabular}{lll}
\verb|\~|&\verb|\\|&\verb|\.|\\
\verb|\1|&\verb|\#|&\verb|\ |
\end{tabular}
\end{center}
Note that `space'\index{space} is a legitimate non-alphabetic character. Since
it is sometimes difficult to see when `space' is meant, from time
to time we will use \verb*| | to indicate a  space which occurs 
between words and\slash or instructions; when  \verb*|\ | is used
it indicates the instruction where a space is the non-alphabetic
character (In \LaTeX\ this instruction actually generates a space).

We do not find  instructions like
\begin{center}
\begin{tabular}{lll}
\verb|\A4|&\verb|\half-sized|&\verb|\up&down|\\
\verb|\1.1|&\verb|\(longer)|&\verb|\m.clark|
\end{tabular}
\end{center}

On the other hand, the \emph{option}s\index{options} may be made up of mixtures
of alphabetic and non-alphabetic characters (as we have already
seen: \verb+11pt+ or \verb+A4paper+). Options are always enclosed by the square brackets. 


The
\textit{argument} to an instruction, is the part in braces (or
\textit{curly} brackets). An instruction with an
argument\index{argument}
\emph{always} requires an argument, although as suggested earlier,
the argument could be `null' -- \verb|\date{}|. Sometimes you may
only specify one of a handful of alternatives, as in the case of the
arguments of \verb|\documentclass|, while in other cases, like
\verb|\author|, you have complete freedom. There are also
instructions which require no argument at all -- \verb|\maketitle|
is an example. The braces\index{braces} are never printed by \LaTeX. Of course,
there are ways to print \verb|{| and \verb|}| or even $\}$ and $\{$,
but we shall look at them later.
 
\begin{question}
What does happen when you specify a non-existent document class, or
a non-existent option? Hint: try it. Advice: Don't Panic (in large
friendly letters).
\end{question}

\section{Trying to correct mistakes} 
If you did the last exercise,  you will have deliberately made
mistakes on input, and will have encountered \LaTeX's error\index{errors}
processing capability. It is possible to correct errors as \LaTeX\ is
running interactively.  If you should successfully
correct the input in this way, you must also remember to correct
the original (assuming you might just need to re-run sometime).
To be more truthful, you may have met both \LaTeX's error
processing, \emph{and} \TeX's. Neither is especially elegant.

One of the most common mistakes is to invoke an instruction
which does not exist -- either because you let intuition
take the upper hand and assume that the instruction must exist, or,
more likely, because you mis-spell it. \LaTeX\ will object:
\begin{verbatim}
! Undefined control sequence.
l.3 \start
          {section}{Start}                   
?
\end{verbatim}                    
\LaTeX\ is trying hard to indicate where the error lies, principally
by breaking the line to indicate just where it has foundered. In the
example above, it is the instruction \verb+\start+. At this point it
is wise to note that (\La)\TeX\ refers to a `control sequence'\index{control
sequence|see{instruction}}, a piece of jargon which is often  replaced by the
word `command'\index{command}, and in this text by
`instruction'\index{instruction}.

Note however that we are left with a \verb|?| prompt. Let's be
intuitive, and assume that \LaTeX\ has something up its sleeve,
like additional help. How do you get help? How about typing
`\texttt{h}'? Lo, something else appears.
\begin{verbatim}
The instruction at the end of the top line
of your error message was never \def'ed. If 
you have misspelled it (e.g., `\hobx'), 
type `I' and the correct spelling (e.g., 
`I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

?
\end{verbatim}
Well, who can understand that? Not very helpful at all. But we've
still been left with a question mark. Let's try `\texttt{h}'  again.
\begin{verbatim}
Sorry, I already gave what help I could...
Maybe you should try asking a human?
An error might have occurred before 
I noticed any problems.
``If all else fails, read the instructions.''
\end{verbatim}
This is one of (\La)\TeX's attempts at humour or light heartedness.
All the same, it is probably good advice.

In response to the `\texttt{?}' prompt, you have several options.
You may type any of the following:
\begin{description} 
\item[\texttt{?}\quad]   where (\La)\TeX\  gives a summary of the following
options: 
\begin{verbatim}
Type <return> to proceed, S to scroll 
future error messages,
R to run without stopping, 
Q to run quietly,
I to insert something, 
E to edit your file,
1 or ... or 9 to ignore the next 1 to 9 
tokens of input,
H for help, X to quit.
\end{verbatim}

\item[\texttt{<return>}\quad]   just prod the \verb|return|
key (or the \verb+enter+ key).  \TeX\ proceeds as 
best it can, until it encounters another
error. 

\item[\texttt{X} or \texttt{x}\quad]  \LaTeX\  stops (eXits); you are
returned to the operating system. Any pages which have
already been completed may not be lost, but the current one will
certainly be lost; the previous one might be as well.

\item[\texttt{E} or \texttt{e}\quad]   this stands for `edit', and
should drop you into an editor. Not all implementations have this linking of
\LaTeX\ and  editors. If you do not drop into an editor, you
will simply be returned to the operating system prompt.
The best way to find out if it does work on your system is to try it.
If it does work you would find yourself editing the erroneous file,
at about the right line -- or rather, where \LaTeX\ thinks the error
occurred. Often it is remarkably close to the error.

\item[\texttt{I} or \texttt{i}\quad]  you may now type text 
to be Inserted at the current place in input. At first this seems
intimidating, but with some practice it does become a viable
route. Its major drawback is that you tend to forget these
`dynamic' corrections.

\item[a number between 1 and 99\quad]  \LaTeX\  deletes
this number of  characters and instructions from input. The
characters or instructions are those which are waiting to be
read -- in other words, \LaTeX\ has not yet `seen' them, or tried
to do anything with them. \LaTeX\ then asks for more information (you
could insert, etc.): \LaTeX\ sees an instruction as a
single item: it also sees a character as a single item --
otherwise termed `token'\index{token} -- for example, \verb|\textbf{bold}| is
seen as the 7 `tokens' \verb|\textbf|, \verb|{|, \verb|b|, \verb|o|, \verb|l|,
\verb|d| and \verb|}|. A space is treated as a
token, \emph{except} when it immediately follows a instruction. 

\item[\texttt{H} or \texttt{h}\quad] 
(\La)\TeX\ gives some sort of help. 

\item[\texttt{S} or \texttt{s}\quad] this is like typing
\verb|<return>| (or \verb|<enter>|) for every subsequent error
message. The error messages are logged, but you have no chance of
interaction. 

\item[\texttt{R} or \texttt{r}\quad] this is like {\tt S}, only
worse; under no circumstances stop. 

\item[\texttt{Q} or \texttt{q}\quad] even even worse; \LaTeX\
suppresses all output to the terminal (goes a lot faster,
subjectively), but perhaps not the best route unless you are very
confident that you know what you are doing, which obviously you
don't, else you would not have made a mistake in the first place.
There is an instruction equivalent, \verb|\batchmode|, which gives a
good clue of when this would be most commonly used.
\end{description}


There is obviously a temptation to just
type \verb|<return>| and let \LaTeX\  surge ahead to report on any
other errors. Unfortunately the corrections \LaTeX\  may have made in
order to do something apparently sensible may lead to other mistakes
later on.  When I don't feel up to mental gymnastics I much prefer
to leave \LaTeX\  (by typing \texttt{x} or \texttt{e}), correct
the error, and then return to \LaTeX. 

\section{Hints}
Don't panic. Error messages are often difficult to fathom, and it
can be easier to solve the problem with reference to your text and
the instructions which were included in the file than to attempt to
understand what the error message is saying. But do not ignore the
messages entirely. Sometimes they can be uncannily accurate and
helpful.

What are the common errors?\index{errors} Failing to balance braces (every
open brace must have a corresponding close brace). This is really
quite difficult to correct through the error reporting and
correction procedure outlined above. If you have a brace open,
\LaTeX\ may do quite a lot of work before you realise that something
has gone wrong. In such a case it is almost impossible to put
things back together in a reasonable way. 
Sometimes this situation manifests itself when processing
finished and you  see a message that 
\begin{verbatim}
(\end occurred inside a group at level 1)
\end{verbatim}
In a similar way, from time to time you might fail to `\verb|\end|'
something you have `\verb|\begin|ned'; again the same message may
appear. More readily apparent, you may \verb|\begin| something but 
\verb|\end| it with the wrong thing. 
 

Mis-types are a frequent
source of problems. After all, if you type \verb+artical+ for
\verb+article+, \LaTeX\ can hardly be expected to divine your
intention. Any instruction  which is presented to \LaTeX\ `incorrectly'
will present a problem. It really does not care about your own
spelling. It does care about the instructions you give it, and since it
thinks you know best, it attempts to follow your orders to the
letter. 

Apart from that, what can go wrong?





 
