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<head>
<title>UK TeX FAQ -- question label underscore</title>
</head><body>
<h3>How to use the underscore character</h3>
<p/>The underscore character &#8216;<code>_</code>&#8217; is ordinarily used in
TeX to indicate a subscript in maths mode; if you type
<code>_</code>, on its own, in the course of ordinary text, TeX will
complain.  If you&#8217;re writing a document which will contain a large
number of underscore characters, the prospect of typing
<code>\</code><code>_</code> (or, worse, <code>\</code><code>textunderscore</code>) for every one of
them will daunt most ordinary people.
<p/>Moderately skilled macro programmers can readily generate a quick hack
to permit typing &#8216;<code>_</code>&#8217; to mean &#8216;text underscore&#8217;.
However, the code <em>is</em> somewhat tricky, and more importantly
there are significant points where it&#8217;s easy to get it wrong.  There
is therefore a package <i>underscore</i> which provides a general
solution to this requirement.
<p/>There is a problem, though: OT1 text fonts don&#8217;t contain an
underscore character, unless they&#8217;re in the typewriter version of the
encoding (used by fixed-width fonts such as <code>cmtt</code>).  So either
you must ensure that your underscore characters only occur in text set
in a typewriter font, or you must use a more modern encoding, such as
T1, which has the same layout for every font, and thus an
underscore in every font.
<p/>If the requirement is only for occasional uses of underscores, it may
be acceptable to use the following construct:
<blockquote>
<pre>
\def\us{\char`\_}
...
\texttt{create\us process}
</pre>
</blockquote><p>
The construction isn&#8217;t in the least robust (in the normal English
sense of the word), but it <em>is</em> robust under expansion (i.e., the
LaTeX sense of the word); so use it with care, but don&#8217;t worry
about section headings and the like.
<dl>
<dt><tt><i>underscore.sty</i></tt><dd><a href="http://mirror.ctan.org/macros/latex/contrib/underscore.zip">macros/latex/contrib/underscore</a> (or <a href="http://mirror.ctan.org/macros/latex/contrib/underscore/">browse the directory</a>); <a href="http://mirror.ctan.org/help/Catalogue/entries/underscore.html">catalogue entry</a>
</dl>
<p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=underscore">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=underscore</a>
</body>