Guide to LaTeX (4th Edition) (Tools and Techniques

118 Chapter 4. Displayed Text
\footnoterule
The command that draws a horizontal line between the page text and
the footnotes. It should not add any net vertical spacing. It may be
changed, for example, by
\renewcommand{\footnoterule}
{\rule{wth}{hght}\vspace{-hght}}
A value of 0 cm for the hght produces an invisible line of zero thickness.
The following style parameters may be changed to redefine how marginal
notes appear:
\marginparwidth
determines the width of the margin box;
\marginparsep
sets the separation between the margin box and the main text;
\marginparpush
is the smallest vertical distance between two marginal notes.
These parameters are all lengths and are assigned new values as usual with the
\setlength command.
4.11 Comments within text
All computer languages provide a means of inserting comments into the
code. These are explanatory notes, documentation, history of development,
or alternative text or code that has been temporarily deactivated.
Comment lines are completely ignored during processing. They are only
intended for human readers inspecting the source text.
In L AT E X, the comment character is the percent sign %. When this
character appears in the text, it and the rest of the line are ignored. If a
comment is several lines long, each line must be prefixed with %.
As for other single character commands, the percent sign itself is
printed with the command \%, as explained in Section 2.5.4.
The comment character % is also useful for experimenting with text
or definitions of user commands or formatting parameters, to try alternatives
without deleting the old versions. By ‘commenting out’ selective
lines, one can play around with variations without losing them.
Large sections of text may be more effectively commented out with the
comment environment from the verbatim package (page 111).
Finally, the % character has an important role to play in suppressing
implied blanks at the end of a line. This is especially desirable in user definitions
where unexpected blanks can creep in between otherwise invisible
declarations with arguments. See Section 8.5.2.
Exercise 4.20: Comment out the changes from Exercise 4.18 in your preamble.
These commands may be reactivated later by removing the % character.