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

396 Appendix B. The L AT E X Clockwork
varioref (Section 9.2.4) defines \vref and \vpageref commands, analogous
to \ref and \pageref, which check if the referenced object is
only one page away, and if so, print text like ‘on the previous page’;
the actual text printed can alternate between two variants.
verbatim (Section 4.9.1) is a re-implementation of the verbatim environment
that prevents memory overflow for long texts; it also defines a
command \verbatiminput to input a file and to print its contents
literally, as well as a comment environment for a block comment in
the input text.
xr (Section 9.2.3) is a package to allow \ref to cross-reference \label
commands from other documents.
xspace (Section 8.3.1 on page 186) contains a device to fix the problem
of command names swallowing up the blank that follows them; thus
the command \PS defined as
\newcommand{\PS}{PostScript\xspace}
may be used as \PS file without having to terminate the \PS
command with \ or {}.
B.6 The various L AT E X files
A number of different files are used during the L AT E X processing: some
are read in while others are created to store information for the next run.
They all consist of two parts:
root name.extension
For every L AT E X document, there is a main file, whose root name is used
when the program L AT E X is called. It normally possesses the extension
.tex, as do any other files that it might read in with \input or \include
commands. (If they have a different extension, it must be given explicitly.)
The other files that are created during a L AT E X processing run normally
have the same root name as the main file but a variety of different extensions,
depending on their functions. If the main file contains \include
commands, there will be additional files created having the same root
names as the included.tex files but with the extension.aux.
Some of these files are created with every L AT E X run, whereas others
appear only when certain L AT E X commands have been issued, such
as \tableofcontents or \makeindex. The .aux files as well as those
produced by special L AT E X commands may be suppressed by including
the command \nofiles in the preamble. This command is useful if a
document is being constantly corrected and reprocessed, so that the information
in the special files is not yet finalized and may therefore be