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+\chapter{Environmentally aware}\label{env}
+\section{Environments}
+\LaTeX\ is environmentally aware! One of the key features
+of \LaTeX\ is the way in which it uses `environments'\index{environment}:
+that is, an `enclosed' structure (which may be part of
+another structure), which has some kind of unity. We have
+already met one environment, the \verb|document|. There
+are a number of other \LaTeX\ environments, all intended
+for slightly different purposes.
+
+Environments have the common feature that they are
+bounded by a \verb|\begin{..}|\index{begin@\texttt{begin}}
+\verb|\end{..}|\index{end@\texttt{end}} pair. You may only ever
+terminate an environment by an environment of exactly the
+same name. However, the \verb|\end{document}| will
+generally close everything, perhaps with a few oblique
+comments from \LaTeX.
+
+\section{Quoting}
+To illustrate an environment, look first at quoting. \LaTeX\
+has two slightly different environments for quoting:
+\verb|quote| and \verb|quotation|. A \texttt{quote}\index{quote@\texttt{quote}}
+is intended for short, perhaps one line, quotations.
+\begin{verbatim}
+\begin{quote}
+Joe Bob says check it out.
+\end{quote}
+\end{verbatim}
+yields
+\begin{quote}
+Joe Bob says check it out.
+\end{quote}
+What do we note about this? The quote is indented to offset it
+from the existing text, and there is a little white space
+above and below. If we had a longer quotation, we would
+be able to see whether the indentation we see was a `normal' paragraph
+indentation or whether the whole quote was indented or whether the whole quote
+is indented:
+\begin{quote}
+I am not now, and never have been, a member of the
+American Communist Party -- \emph{attributed to Mao Xedung}.
+\end{quote}
+Obviously it applies to all lines.
+
+The other alternative is \verb|quotation|\index{quotation@\texttt{quotation}},
+which is really designed for longer quotations containing several
+paragraphs:
+\begin{quotation}
+I know your works, that you are neither hot or cold: I would that you were
+either hot or cold.
+
+But because you are lukewarm, neither hot or cold, I will spit
+you out.
+\end{quotation}
+which may be obtained from
+\begin{verbatim}
+\begin{quotation}
+I know your works, that you are neither
+hot or cold:
+I would that you were either hot or cold.
+
+But because you are lukewarm,
+neither hot or cold, I will spit you out.
+\end{quotation}
+\end{verbatim}
+
+\begin{question}
+Use the \texttt{quotation} environment to produce a piece of
+quoted text. If your mind is a complete blank, you could
+always try:
+\begin{verbatim}
+It's one hundred and six miles to Chicago;
+we got a full tank of gas, half a pack of
+cigarettes, it's dark, and we're wearing
+sunglasses.
+
+Hit it.
+\end{verbatim}
+\end{question}
+
+\section{Verse or worse}
+Lamport introduces another environment
+which he describes thus:
+\begin{quote}
+Poetry is displayed with the \texttt{verse} environment.
+\end{quote}
+Few poets would want to have their work described as
+verse\index{vers@\texttt{verse}}, and even fewer would use the \texttt{verse}
+environment to present it. However, the environment is
+not without its uses.
+And in fact, to be `fair' it has some rather appealing
+qualities. Unlike every other situation we have seen so
+far, \LaTeX\ asks that you do the line breaking\index{line breaking} yourself
+in the \texttt{verse} environment. Do this by terminating a
+line with \verb|\\|\index{backslash}. As we shall discover, this works in all
+sorts of other places too.
+%\begin{verbatim}
+\begin{verse}
+Bring me my Bow of burning gold:\\
+Bring me my Arrows of desire:\\
+Bring me my Spear: O clouds unfold!\\
+Bring me my Chariot of fire!
+\end{verse}
+%\end{verbatim}
+was produced from
+\begin{verbatim}
+\begin{verse}
+Bring me my Bow of burning gold:\\
+Bring me my Arrows of desire:\\
+Bring me my Spear: O clouds unfold!\\
+Bring me my Chariot of fire!
+\end{verse}
+\end{verbatim}
+
+One feature may be worth emphasising. The last line of a stanza does not
+have to end with \verb+\\+. Since it is immediately followed by
+\verb+\end{verse}+ there is no need to introduce an additional (and
+therefore redundant) instruction.
+\begin{question}
+Find out what happens when you end the last line with \verb+\\+. Does
+\LaTeX\ handle it in an elegant and friendly way?
+\end{question}
+
+
+
+Lamport clearly had Blake in mind when he created the
+{\tt verse} environment, since lines which are too long
+for the page width wrap over nicely, with a little bit
+of extra indentation:
+\begin{verse}
+Excess of sorrow laughs. Excess of joy weeps.\\
+The roaring of lions, the howling of wolves, the raging
+of the stormy sea, and the destructive sword, are
+portions of eternity too great for the eye of man.\\
+The fox condemns the trap, not himself
+\end{verse}
+
+There are two other features of note here. The first is that the \verb|\\|
+instruction has a variant\index{variant} form, the \texttt{*}\index{asterisk@*}
+form. If you write \verb|\\*|, \LaTeX\ will not allow the page to be
+broken at that point. This useful feature is
+an example of a variant form for the instruction. We will find that many
+\LaTeX\ instructions have a \verb|*| variant, which modifies
+the default way in which the instruction is handled.
+
+The second feature is that the instruction may take an optional\index{options}
+argument. We have met optional arguments before, and we shall meet them again and
+again. Optional arguments are always enclosed in square brackets --
+\mbox{\texttt{[}\thinspace\texttt{]}}. Here the optional argument allows us to
+specify how much additional space to leave between lines -- a
+\emph{dimension}\index{dimensions} is specified, complete with its units. In the
+case of the
+\verb+\\+ instruction we would have something like \verb+\\[0.5cm]+ where some
+dimension, in this case 0.5\,cm, was specified in the square brackets. This is
+similar to the optional arguments we have already met for
+\verb|\documentclass|, except that
+\verb|\documentclass| also requires an argument in braces. Once we know
+what units we can use, this optional argument offers some useful
+possibilities.
+
+\section{Units\index{units} -- a digression}\label{units}
+We have come a long way, without any real reference to the sizes\index{size} of
+things, except fonts. In general, we shouldn't be too concerned with sizes of most
+things on the page, since the selection of the document style implicitly
+specifies many of the relationships and sizes of parts of the document.
+Nevertheless, there are times when we want to do something particular,
+where we must somehow specify a size.
+
+\begin{table*}
+\begin{center}
+\begin{tabular}{|cll|}
+\hline
+abbreviation & name & conversion\\
+\hline
+ pt & point & \\
+ pc & pica & 1\thinspace pc=12\thinspace pt \\
+ in & inch & 1\thinspace in=72.27\thinspace pt \\
+ bp & big point & 72\thinspace bp=1\thinspace in \\
+ cm & centimeter & 1\thinspace in=2.54\thinspace cm \\
+ mm & millimeter & 10\thinspace mm=1\thinspace cm \\
+ dd & did\^ot point & 1157\thinspace dd=1238\thinspace pt \\
+ cc & cicero & 1\thinspace cc=12\thinspace dd \\
+ sp & scaled point & 65536\thinspace sp=$2^{16}$sp=1\thinspace pt \\
+ em & width of `M' & (current font)\\
+ ex & height of `x' & (current font)\\
+\hline
+\end{tabular}
+\end{center}
+\caption{Units\index{units} used in \LaTeX\ to specify dimensions}\label{tunit}
+\end{table*}
+
+Table \ref{tunit} shows the units which \LaTeX\ `knows' about,
+together with their conversions. To specify a dimension, say
+\verb|12pt|, \verb|0.7pc| or \verb|12in|, or even \verb|12 pt|, \verb|0.7 pc|
+or \verb|12 in| if you find that easier to write or read. If you inadvertently
+say \verb|12inches|, \LaTeX\ will assume that the \verb|12in| is the
+dimension, and that the \verb|ches| is text to be printed. Of course
+\verb|12points| wouldn't even be understood and would generate an error.
+
+(\La)\TeX\ uses the conversions as \emph{exact}
+ratios -- in other words, even if they are not the exact and true
+conversions, they are what \LaTeX\ uses (this ensures a degree of
+standardisation within \LaTeX). Any value preceding one of these units
+may be specified as either a whole (integer) number, or one with a decimal
+point (decimal numbers would not make much sense in the case of `scaled
+points'). \LaTeX\ does not support mixtures of units, so that `two picas
+and four points' would not be acceptable, except as 2.3333333pc or 28pt.
+
+You do not have to stick to any particular dimensions throughout your
+document. Mix metric, Imperial and printers' dimensions as you wish. The
+printer's point\index{points} makes some sort of sense as a base unit, since all
+the fonts are described in terms of their `point' size. But outside that
+particular area, any other `size' can be described in any of the above
+dimensions. If you do not include a dimension, \LaTeX\ will often assume
+points are meant; it is safer to give the dimension. If the dimension is
+zero, it still needs units.
+
+The \verb|em|\index{em} and \verb|ex|\index{ex} deserve a little more
+explanation. They are the only two `relative measures'. In
+typographic terms, an em (also known as a \emph{mutton}) is a horizontal
+measure (being approximately the width of a capital `M' in the \emph{current}
+font), while an ex (also known as an \emph{en-nut}) is a vertical measure (the
+height of an `x' in the \emph{current} font). If you change font, the values of
+em and ex will also change. Although an em is intended as a horizontal
+measure, it will be possible to use it in a vertical sense: similarly, the ex
+may be used for horizontal amounts. \LaTeX\ is not that picky.
+
+\subsection{The point}
+In this sort of situation, in verse, it is more
+general to specify a distance which is related in some way to the font in
+use: a relative rather than an absolute figure:
+\begin{verse}
+Our plesance here is all vain glory,\\
+This fause warld is but transitory;\\
+The flesh is brukle, the Fiend is slee:\\*[2ex]
+\emph{Timor mortis conturbat me.}
+\end{verse}
+The `refrain' is separated from the rest of the poem by an additional
+2\,ex, obtained by terminating the line preceding the refrain by
+\verb|\\[2ex]|:
+\begin{verbatim}
+The flesh is brukle, the Fiend is slee:\\[2ex]
+\end{verbatim}
+\begin{question}
+Try that last example, but use different units. How would you leave a gap
+which was equivalent to a blank line?
+\end{question}
+\section{Lists}
+If \LaTeX\ is remembered for nothing else, it will be
+remembered for the way in which Lamport elevated the
+`list'\index{lists} into a common, powerful, all-pervading structure.
+The more I think about it, the more I see myself
+surrounded by documents which are most effectively
+presented as lists, or lists within lists. As a technique
+for structuring an argument, and giving relative weights
+to various parts and sub-parts, it can be enlightening and fundamental.
+
+\LaTeX\ has three basic list structures, each with
+slightly different attributes and visual properties.
+There are also facilities to extend these. The structures
+are\index{index@\texttt{itemize}}\index{enumerate@\texttt{enumerate}}\index{description@\texttt{description}}
+\begin{itemize}
+\item enumerate
+\item itemize
+\item description
+\end{itemize}
+Of course, this is a list! It was generated by
+\begin{verbatim}
+\begin{itemize}
+\item enumerate
+\item itemize
+\item description
+\end{itemize}
+\end{verbatim}
+Now we have (almost) the whole syntax\footnote{You should
+be able to guess that there are probably some optional
+arguments lurking about somewhere. There usually are.} of
+these list-making environments.
+
+As usual, the environment must be terminated with the
+correct name.
+
+\begin{question}
+Try doing something like this:
+\begin{verbatim}
+\begin{itemize}
+\item just a word or two
+\item and another one
+\end{enumerate}
+\end{verbatim}
+The error message which \LaTeX\ gives in this
+context is very annoying:
+\begin{verbatim}
+! \begin{itemize} on input line 3 ended
+ by \end{description}.
+\end{verbatim}
+It is informative that \LaTeX\ stops at this point, but
+also helpful that it will allow you to continue. A pity it misleads.
+\end{question}
+
+If you are an \texttt{emacs} guru, or have another similarly
+powerful editor\footnote{Correctly, \texttt{emacs} is a way
+of life. Like (\La)\TeX, there is nothing \texttt{emacs} cannot do,
+in the right hands.}, and skill, you could ensure that your
+\verb|\begin{..}| was always terminated
+correctly.
+
+\subsubsection{Itemizing}
+Using the \verb|itemize|\index{itemize@\texttt{itemize}} environment, each item
+is marked in some way. Different levels of itemization are given
+different symbols. This implies that you can
+nest itemization instructions. In fact, you can nest the
+whole concept of environments in general, and lists in
+particular\footnote{Almost true; don't go too deep.}.
+
+\begin{question}
+Find out what the symbols are for the various levels of
+itemization.
+\end{question}
+\begin{question}
+Find out just how deeply you can nest itemization.
+\end{question}
+
+\subsubsection{Enumerating}
+As you may guess, the \texttt{enumerate} environment numbers each
+item\index{enumerate@\texttt{enumerate}}. This implies that there must be a
+counter marching away somewhere, incrementing each time \verb|\item| is
+encountered. And so there is. There may be several, since we can, as
+usual, nest enumeration too.
+\begin{question}
+Find out what happens when you nest levels of
+enumeration. For example, you could use one of your last exercises,
+changing the \verb|\begin{itemize}| to \verb|\begin{enumerate}|.
+Remember to change the \verb|\end| too.
+\end{question}
+\begin{question}
+Now nest enumeration within itemization (or even
+itemization within enumeration).
+\end{question}
+
+\subsubsection{Describing}
+In the \verb|description|\index{description@\texttt{description}} environment,
+you
+\emph{must} provide an optional (\emph{sic}) argument on the \verb|\item|.
+This argument will be the `key' to the list. In the
+previous list environments, \LaTeX\ generated something
+(a symbol, or a number\slash letter) to mark each \verb|item|.
+This time, you have to provide the `mark':
+\begin{verbatim}
+\begin{description}
+\item[aardvark] mainly harmless --
+as in ``aardvark never hurt anyone''.
+\item[Betty Boop] a pleasure and a
+delight. One of \emph{the} great artistes.
+\item[crow] family of birds including the
+magpie (\textsl{pica pica})
+\end{description}
+\end{verbatim}
+which comes out looking like
+\begin{description}
+\item[aardvark] mainly harmless -- as in ``aardvark never
+hurt anyone''.
+\item[Betty Boop] a pleasure and a delight. One of \emph{the}
+great artistes.
+\item[crow] family of birds including the magpie (\textsl{pica pica})
+\end{description}
+\begin{question}
+Perhaps I exaggerate when I say that this environment requires an optional
+argument. Demonstrate what happens if you omit the optional argument on the
+\verb+\item+s in \verb+description+. Or whether the other list environments
+may take optional arguments.
+\end{question}
+\begin{question}
+It has always seemed to me that these three basic list environments are not
+well named -- with two verbs and a noun. Devise a better and more consistent
+set of names. \textsc{Html} uses the rather terse \texttt{ol} (ordered list),
+\texttt{ul} (unordered list), and \texttt{dl} (data list).
+\end{question}
+%%%%%%%%%%%inserted section 3-e.tex
+\section{Read my lips}
+Another two pairs of environments may be useful. As these
+notes show, it is often useful to be able to express chunks
+of text in typrewriter form -- that is `verbatim', where
+every symbol is recorded as it was typed in. This may not be
+a frequent requirement. \LaTeX\ has a \verb+verbatim+ environment
+which will handle this. Obviously it has to turn off lots of \LaTeX's normal
+processing, and as a result there are some limitations. When the environment is
+ended, the \verb+\end{verabtim}+ must occur on a line by itself. A variant is
+the *-form, where any blanks (spaces) within the material will be printed out
+as \verb*+ +. Besides needing to be able to present chunks of text literally,
+it may also be necessary to do this for odd symbols or words. The command
+\verb+\verb+ is provided for this. For example, if we write
+\begin{verbatim}
+The backslash, \verb+\+, introduces every instruction, with a few
+exceptions, including \verb=~=.
+\end{verbatim}
+then the result will be
+\begin{quote}
+The backslash, \verb+\+, introduces every instruction, with a few
+exceptions, including \verb=~=.
+\end{quote}
+Note how \verb+\verb+ works. The material which is to be expressed verbatim is
+`enclosed' within a pair of repeated arbitrary symbols. The only symbols which
+may not be used are \verb+*+, since there is a variant, \verb+\verb*+, where
+any enclosed blanks are again represented by \verb*+ +. For example
+\begin{verbatim}
+The tag \verb*+< html>+ will not be
+recognized, since the space (\verb*+ +)
+after the \verb+<+ should not be present
+\end{verbatim}
+would give us
+\begin{quote}
+The tag \verb*+< html>+ will not be recognized, since
+the space (\verb*+ +) after the \verb+<+ should not be present
+\end{quote}
+Although line endings are respected in the \verb+verbatim+ environment,
+ you should not have a line end in the body of a \verb+\verb+. This is seldom a
+problem, but if you use an editor which wraps (like \Textures), you may
+inadvertantly break a \verb+\verb+ over a line. \LaTeX\ will note the error.
+Another important factor is that neither of these instructions may appear in
+the argument of another instruction.
+
+
+The sister environment to \verb+verbatim+ is \verb+alltt+. This is identical,
+except that \verb+\+, \verb+{+ and \verb+}+ all have their `normal' meanings.
+We may therefore have
+\begin{verbatim}
+\begin{alltt}
+Even in text we need to \textsl{slant}
+\end{alltt}
+\end{verbatim}
+to yield
+\begin{quote}
+\begin{alltt}
+Even in text we need to \textsl{slant}
+\end{alltt}
+\end{quote}
+If we wish to use this feature we should first ensure that the \verb+alltt+
+package is loaded. We'll cover this aspect a little later.
+
+\section{One paragraph at a time}
+The other major environments are connected with the setting of paragraphs. In
+a later chapter we will look at how \LaTeX\ actually handles the
+setting of text. In the mean time we will note that sometimes it does not
+manage to align the right margin and complains of `overfull boxes'. There are
+many solutions to this. One is to provide \LaTeX\ with more flexibility in
+setting the paragraph. This can be translated as `being more sloppy'. The two
+environments \verb+sloppypar+ and \verb+fussypar+ are provided to handle this.
+The default is \verb+fussypar+, and therefore it is unclear just why you might
+want to switch it on, when a `sloppy' set of paragraphs can be delimited
+easily. Note this is a paragraph matter. Since \LaTeX\ does its
+typesetting on a paragraph by paragraph basis, there is no point trying to set
+part of a paragraph `sloppy' and part `fussy'. The concept just does not exist.
+
+An alternative to this \verb+sloppypar+ environment is to use the instruction
+\verb+\sloppy+. There is a corresponding
+\verb+\fussy+ instruction too. One of \LaTeX's quirks, a consequence
+of treating text on a paragraph basis, is that the inclusion of
+one of these instructions within a paragraph, whether at the end or the
+beginning, turns the whole paragraph into that style; and of course every
+following paragraph too, unless you issue new instructions, or are careful to
+limit the action in some other way.
+
+
+
+It is also possible to exercise control over the way \LaTeX\ sets lines within
+paragraphs. Normally \LaTeX\ spreads out the space between words to have both
+the right and left margins aligned vertically -- set `flush left' and
+`flush right'
+(or \emph{justified}). If, instead of adjusting the space,
+it is made constant, the left margin remains fixed and a ragged
+right margin would appear. The \verb+flushleft+ environment has this effect.
+Its mirror-twin, \verb+flushright+ will make the left margin ragged. And a third
+variant may be more useful, \verb+center+, where the text is effectively
+centred around the middle axis. Taken with \verb+\\+ to break lines, this is
+sometimes a useful way of creating title information. All three of these
+environments have corresponding instructions: respectively they are
+\verb+\raggedright+, \verb+\raggedleft+ and \verb+\centering+. Again, recall that
+these instructions and environments will apply to whole paragraphs.
+
+Observation will demonstrate that the \verb+verse+ environment is set
+ragged right, presumably to minimise
+hyphenation, while \verb+quotation+ is justified.
+
+\subsection{More to come}
+This is was just a glimpse of the environments available in \LaTeX.
+A few more will crop up. It makes little sense to present
+ \emph{all} the environments at once, especially
+when they each have quite different functions. The key
+things to note are
+\begin{itemize}
+\item that they must be enclosed by the same
+identifier or label (e.g.~\texttt{quote} or \texttt{itemize}),
+\item that they \emph{may} have
+optional arguments,
+\item and that they may not overlap.
+\end{itemize}
+
+\section{Sections\index{sections} and the like}
+Many (most) documents can be thought of as highly
+hierarchical, with a subdivision into successively
+smaller units, down the scale through `parts',
+`chapters', `section', `subsections', right down through
+`paragraphs'\index{paragraphs} to sentences and even words. \LaTeX\ recognizes
+this and provides a set of `sectioning' instructions, shown in
+Table~\ref{tsect}
+\begin{figure*}
+\begin{center}
+\begin{tabbing}
+\makebox[1.5in]{}\=\verb|\part|\\
+\>\quad\=\verb|\chapter|\\
+\>\>\quad\=\verb|\section|\\
+\>\>\>\quad\=\verb|\subsection|\\
+\>\>\>\>\quad\=\verb|\subsubsection|\\
+\>\>\>\>\>\quad\=\verb|\paragraph|\\
+\>\>\>\>\>\>\quad\=\verb|\subparagraph|
+\end{tabbing}
+\end{center}
+\caption{The sectional hierarchy}\label{tsect}
+\end{figure*}
+
+Now, note that we do not in fact go down right to the
+sentence or word level. And also note that Lamport's
+\verb|\paragraph|\index{paragraph@\texttt{paragraph}} and \verb|\subparagraph|
+are not really paragraphs at all. Lamport merely says
+\begin{quote}
+``The names \dots\ are unfortunate, since they usually
+denote units that are usually composed of several
+paragraphs; they have been retained for historical
+reasons.''
+\end{quote}
+Make of that what you will.
+
+Each sectioning instruction requires an `argument' -- its own
+title. Since this is mandatory, it appears in braces.
+(Remember that only optional arguments appear in square
+brackets.)
+
+What do we get out of sectioning? It is easiest to see by
+trying it out. As you will have realised, this document
+is produced with \LaTeX. We have already used
+\verb|\chapter|\index{chapter@\texttt{chapter}} at the beginning of this
+`section', using the statement
+\begin{verbatim}
+\chapter{Environmentally aware}
+\end{verbatim}
+Somehow, \LaTeX\ managed to work out that this is the
+chapter~\ref{env}, and arranged for the details to be
+printed out. So one of the things going on in the
+background is to keep track of the level of the
+sections. Similarly, this particular section started with a
+\begin{verbatim}
+\section{Sections and the like}
+\end{verbatim}
+instruction. Again, \LaTeX\ kept track of the levels. Notice
+too that it presented the information in different ways.
+There are no sub-sections here, but we could invent a few:
+\begin{verbatim}
+\section{Sections}
+In article and report, section is the
+ highest level.
+\subsection{Subsections}
+After the section comes the subsection.
+\subsubsection{Subsubsection}
+After that comes the subsubsection.
+\paragraph{Paragraph}
+Then we have paragraphs which run on
+ immediately after the paragraph label.
+\subparagraph{Subparagraph}
+And at the very lowest level, the
+ subparagraph, which, like the paragraph
+ runs on.
+\end{verbatim}
+ yields Figure~\ref{sectioning} where the slight reduction in size is
+deliberately introduced to highlight these sub-divisions.
+Each of these sections must contain something, if only a lower level unit.
+At the lowest unit, there must be some text.
+
+
+\begin{figure*}
+\begin{center}
+\begin{minipage}{0.75\textwidth}
+\small
+\textbf{\large 3\quad Sections}\\[0.4\baselineskip]
+In article and report, section is the highest level.\\[0.75\baselineskip]
+\textbf{\normalsize 3.2\quad Subsections}\\[0.4\baselineskip]
+After the section comes the subsection.\\[0.75\baselineskip]
+\textbf{3.2.1\quad Subsubsection}\\[0.4\baselineskip]
+After that comes the subsubsection.\\[0.75\baselineskip]
+\textbf{Paragraph}\quad
+Then we have paragraphs which run on immediately after the paragraph
+label.\\[0.75\baselineskip]
+\textbf{Subparagraph}\quad
+And at the very lowest level, the subparagraph, which, like the paragraph runs
+on.
+\end{minipage}
+\end{center}
+\caption{Sub-divisions from Section to Subparagraph\label{sectioning}}
+\end{figure*}
+
+
+
+
+\begin{question}
+This book makes no real use of \verb|\paragraph| and \verb|\subparagraph|
+since its author doesn't think in those terms. Find out how \LaTeX\
+actually handles the text which follows these sectioning instructions. The
+results may not be entirely anticipated.
+\end{question}
+
+ Naturally, in order to begin
+(say) a subsection, you will already have begun a section. And equally
+naturally, you may expect to have several subdivisions within a division.
+On the other hand, as may be obvious here, the
+\verb|book| style does not require the presence of
+\verb|\part|. It can start with a \verb|\chapter|.
+Similarly, the \verb|\article| style does not use
+\verb|\chapter| at all. This does mean you can string all
+your articles together into a book, all too easily, just
+by a few easy edits.
+
+\begin{question}
+Demonstrate what happens when you nest the sectioning (subsectioning,
+subsubsectioning\dots) instructions inconsistently.
+\end{question}
+
+What else have we gained? The table of contents\index{table of
+contents}\index{contents} at the beginning is also generated automatically as a
+result of creating sections. Now, examine the table of contents
+carefully to determine which levels are actually
+reflected in the table of contents which is created. The section
+`argument' (the bit in braces) goes into the table of contents ({\em
+toc}) in its entirety. The entry may also be used to change the
+running head\index{running head}\index{head} (at the top of the
+page)\footnote{not here, because the \BV\ house style over-rides this.}.
+
+\LaTeX\ allows you to modify the behaviour of the
+sectioning\index{sections} instructions in two main ways:
+\begin{enumerate}
+\item we may wish a different entry
+to appear in the table of contents from the `body'; or
+\item we may not wish the entry to appear in the table of contents, or
+the running head (and by implication, not to be numbered).
+\end{enumerate}
+
+Both these requirements may be fairly readily
+accommodated.
+Changing the table of contents `\texttt{toc}' entry is readily
+accomplished by adding an optional argument:
+\begin{verbatim}
+\subsection[What I really
+want to appear]{Sub-sub-section}
+\end{verbatim}
+This optional argument will now appear in the table of contents
+in place of the entry which introduces the subsection.
+Limiting the action, and producing a `simple' entry
+is possible through the \verb|*| form\index{variant}. This is another of the
+instructions which have a variant form, followed immediately by the~\verb|*|.
+In this case, it would appear as
+\begin{verbatim}
+\subsubsection*{An almost anonymous entry}
+\end{verbatim}
+This also suppresses the increments in the
+counter for this particular subsection.
+%\end{itemize}
+
+
+\section{Table of contents}
+Having mentioned the presence of a table of contents (or
+a \emph{potential} table of contents), we have to say a
+little more about it. This is not generated unless you do
+actually ask for it. How do you ask for it?
+Say\index{tableofcontents@\texttt{tableofcontents}}
+\begin{verbatim}
+\tableofcontents
+\end{verbatim}
+and \LaTeX\ will insert the table of contents at that
+point. Now, if the table of contents appears somewhere at the beginning
+of the document, how does \LaTeX\ `anticipate' what the section
+descriptions are to be?
+Since it cannot know, what actually happens is
+that you run your \LaTeX\ file several times. The first
+time round \LaTeX\ generates a new file of the same name,
+but with a \verb|.toc|\index{toc@\texttt{.toc}} extension. It is this file which
+is read the second time around. Note that it might still
+be out of step, if you have edited the file in between.
+Essentially what has to happen is that the very final,
+unchanged file has to be run \emph{at least} twice to resolve the table
+of content entries (recall that it includes the page
+numbers too).
+
+\section{Other background activity}
+Although we have not touched on figures and tables (yet),
+there are similar instructions which allow list of figures and tables to be
+generated. A similar sort of process goes on. A special
+file is generated which contains information about the
+list of figures, the list of tables, or even a glossary
+or an index. The instructions for lists of figures and
+tables are:
+\begin{verbatim}
+\listoffigures
+\listoftables
+\end{verbatim}
+and the files they write are given the extensions
+\verb|.lof|\index{lof@\texttt{.lof}} and
+\verb|.lot|\index{lot@\texttt{.lot}}. In
+fact, you will find that
+\LaTeX\ can be altogether profligate, creating all sorts
+of other files, usually with the main file's name, but
+different extensions. Every \LaTeX\ job creates a
+\verb|.log|\index{log@\texttt{.log}} and an
+\verb|.aux|\index{aux@\texttt{.aux}} file. The log file can give
+a lot of information about what
+is going on. Sometimes some of it is useful. Typically
+a log is produced as you run the file through \LaTeX, but
+more information will be inserted into the \verb+.log+ file, which may
+be consulted later. The `auxiliary' file is more specific and
+contains some useful information for subsequent \LaTeX\ runs. It is not
+intended for reading by people, just \LaTeX.
+
+The truth is simply that we very
+rarely get everything finished, or right, the first time
+around -- it is so tempting to run a bit through \LaTeX\
+and see if it looks any good. In passing we could
+demolish the myth that electronic document preparation
+saves any time or money, or that office productivity tools have anything to
+do with increasing productivity. When you can make the corrections yourself,
+you do, using your time, which is costly. And you seek perfection, because you
+know it is attainable. Before, you were just grateful to get something --
+anything.
+
+Most of these extra `information' files are there solely for
+\LaTeX, and are of little direct use to us (except in terms of what they will
+allow us to do). They are just about human readable, but why bother? Perhaps
+the key thing to note though is that if you send off your \LaTeX\ file to
+someone else, or receive one from someone else, you
+really should expect to have it run through your document at least twice before
+it looks as it should. This is a bit unexpected for the naive
+or inexperienced.
+
+
+
+\begin{question}
+Now have a look and see what extra files \LaTeX\ appears
+to have generated for you. Look too at an old \verb|.log|
+file to see the information which \LaTeX\ will have
+issued about these extra files. As usual, it is often
+difficult to distinguish the useful material from the
+rather less useful material (`garbage'). We really need a
+\verb|.junk| file too.
+\end{question}
+
+
+%\mbox{\verb|[|\thinspace\verb|]|}. Here the optional argument allows us to
+
+\begin{question}
+One of the things that puzzle me about
+\LaTeX\ is why sections are not environments, or even
+lists. \LaTeX\ will permit you to write something like
+\begin{verbatim}
+\begin{itemize}
+\section{...
+\begin{quote}
+\section{.....
+\end{quote}
+.
+.
+\end{itemize}
+\end{verbatim}
+While I can see that the section may be part of an
+environment, I am surprised that it can span environments
+in this way.
+
+Any explanations?
+\end{question}