@Section
    @Title { Large-scale structure:  chapters, sections, etc. }
    @RunningTitle { Large-scale structure }
    @Tag { largescale }
@Begin
@PP
Lout's large-scale structure symbols vary with the type of document
large.scale. @Index { large-scale structure }
({@Code "@Chapter"} for books, @Code "@Overhead" for overhead
transparencies, etc.), but they all work in the same way.  Here is a
typical example, {@Code "@Section"}, as it would actually be used:
@ID @OneRow @Code {
"@Section"
"    @Title { Allocation of teachers }"
"@Begin"
"@PP"
"Apart from the usual need to avoid clashes, the allocation of teachers must"
"ensure that no teacher teaches more than seven periods per day, or ..."
"@End @Section"
}
First comes the symbol itself, then any options in the usual way, and
then the following object, enclosed in @Code "@Begin" and
{@Code "@End @Section"}.  The following object, also called the body
of the section, may contain paragraphs, displays, and all the other
features as usual.  The body should begin with a paragraph symbol,
which may be @Code "@PP" or @Code "@LP" as you prefer.  The result is
a section like the present one, automatically numbered, with the
@Code "@Title" option for its heading, preceded by a conditional new
title. @Index @Code "@Title"
page symbol (Section {@NumberOf paragraphs}).
@PP
When @Code "@Section" symbols are used within an ordinary document, they
must be bracketed by @Code "@BeginSections" and @Code "@EndSections"
symbols, like this:
@ID @OneRow @Code {
"@SysInclude { doc }"
"@Doc @Text @Begin"
"preceding text"
"@BeginSections"
"@Section ... @End @Section"
"@Section ... @End @Section"
"..."
"@Section ... @End @Section"
"@EndSections"
"@End @Text"
}
This arrangement is reminiscent of the one for lists, and, as for
lists, there may be no paragraph or new page symbols before, between,
or after the sections.  To change the gap between sections, you need
to change the @Code "@SectionGap" option in the setup file, as explained
in Chapter {@NumberOf types}.
@PP
The @Code "@Begin ... @End @Section" that brackets the body of each
section may be abbreviated to {@Code "{ ... }"}.  However, the long
form is recommmended because it helps Lout to detect missing or extra
braces within the body of the section.
@PP
All large-scale structure symbols have a @Code "@Tag" option, whose
use is explained in Section {@NumberOf cross}, and a @Code "@RunningTitle"
runningtitle. @Index @Code "@RunningTitle"
option.  If running page headers have been requested, @Code "@RunningTitle"
will be used if it is given, otherwise @Code "@Title" will be used for the
running header.  For example, the present section begins like this:
@ID @OneRow @Code {
"@Section"
"    @Title { Large-scale structure:  chapters, sections, etc. }"
"    @RunningTitle { Large-scale structure }"
"    @Tag { largescale }"
"@Begin"
"..."
}
The point is that the section title is rather long for a running
title, and so we use @Code "@RunningTitle" to get an abbreviated
version of it.
@PP
All large-scale structure symbols also have an @Code "@InitialLanguage"
option which sets the current language for the duration of that
symbol.  However, footnotes, endnotes, figures, tables, references,
and index entries are set in the initial language of the document as
a whole, unless you change their language explicitly using the
@Code "@Language" symbol.
@End @Section
