@Section
   @Title { Multiple columns }
   @Tag { columns }
@Begin
@PP
You can change the number of columns of text per page, and the width of
columns. @Index columns
multiple.columns @Index { multiple columns }
the gap between the columns, by changing these two setup file options:
columnnumber. @Index @Code "@ColumnNumber"
columngap. @Index @Code "@ColumnGap"
@ID @OneRow @Code {
"@ColumnNumber { 1 }"
"@ColumnGap { 1.00c }"
}
If you are using your own setup file (Section {@NumberOf setup}), you can
find and change them there.  If not, @Code "@ColumnNumber" may be changed
at the beginning of your document (Section {@NumberOf ordinary}).
@PP
@Code "@ColumnNumber" may be any number between 1 and 10, with default
value 1 as shown, and @Code "@ColumnGap" may be any length (Section
{@NumberOf objects}).  The column width is derived from these options
column.width @RawIndex { column width }
column.width.pages @SubIndex { on pages }
using the obvious formula
@ID @Eq { columnwidth = { pagewidth - margins -
({@Code "@ColumnNumber"} - 1) times {@Code "@ColumnGap"} }
over @Code "@ColumnNumber"
}
You must ensure that this comes to something reasonable.
@PP
These two options do not apply to pages containing an index.  For them
there are similar setup file options called @Code "@IndexColumnNumber"
and @Code "@IndexColumnGap" (Section {@NumberOf indexes}).
@PP
Most document types permit you to have multiple columns, but certain
things will be kept full width regardless of the @Code "@ColumnNumber"
option:  figures and tables, chapter headings, and so on.  The details
vary with the document type, so are deferred to Chapter {@NumberOf types}.
@End @Section