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<h4 class="subsection">9.1.2 <code>@code</code>{<var>sample-code</var>}</h4>
<p><a name="index-code-401"></a>
<a name="index-Syntactic-tokens_002c-indicating-402"></a>Use the <code>@code</code> command to indicate text that is a piece of a
program and which consists of entire syntactic tokens. Enclose the
text in braces.
<p><a name="index-Expressions-in-a-program_002c-indicating-403"></a><a name="index-Keywords_002c-indicating-404"></a><a name="index-Reserved-words_002c-indicating-405"></a>Thus, you should use <code>@code</code> for an expression in a program, for
the name of a variable or function used in a program, or for a
keyword in a programming language.
<p>Use <code>@code</code> for command names in languages that resemble
programming languages, such as Texinfo. For example, <code>@code</code> and
<code>@samp</code> are produced by writing ‘<samp><span class="samp">@code{@@code}</span></samp>’ and
‘<samp><span class="samp">@code{@@samp}</span></samp>’ in the Texinfo source, respectively.
<p><a name="index-Case_002c-not-altering-in-_0040code_007b_0040_0040code_007d-406"></a>It is incorrect to alter the case of a word inside an <code>@code</code>
command when it appears at the beginning of a sentence. Most computer
languages are case sensitive. In C, for example, <code>Printf</code> is
different from the identifier <code>printf</code>, and most likely is a
misspelling of it. Even in languages which are not case sensitive, it
is confusing to a human reader to see identifiers spelled in different
ways. Pick one spelling and always use that. If you do not want to
start a sentence with a command name written all in lower case, you
should rearrange the sentence.
<p>In the printed manual, <code>@code</code> causes TeX to typeset the
argument in a typewriter face. In the Info file, it causes the Info
formatting commands to use single quotation marks around the text.
For example,
<pre class="example"> The function returns @code{nil}.
</pre>
<p class="noindent">produces this:
<blockquote>
The function returns <code>nil</code>.
</blockquote>
<p>Here are some cases for which it is preferable <em>not</em> to use <code>@code</code>:
<ul>
<li>For shell command names such as <samp><span class="command">ls</span></samp> (use <code>@command</code>).
<li>For shell options such as ‘<samp><span class="samp">-c</span></samp>’ when such options stand alone (use
<code>@option</code>).
<li>Also, an entire shell command often looks better if written using
<code>@samp</code> rather than <code>@code</code>. In this case, the rule is to
choose the more pleasing format.
<li>For environment variable such as <samp><span class="env">TEXINPUTS</span></samp> (use <code>@env</code>).
<li>For a string of characters shorter than a syntactic token. For example,
if you are writing about ‘<samp><span class="samp">goto-ch</span></samp>’, which is just a part of the
name for the <code>goto-char</code> Emacs Lisp function, you should use
<code>@samp</code>.
<li>In general, when writing about the characters used in a token; for
example, do not use <code>@code</code> when you are explaining what letters
or printable symbols can be used in the names of functions. (Use
<code>@samp</code>.) Also, you should not use <code>@code</code> to mark text
that is considered input to programs unless the input is written in a
language that is like a programming language. For example, you should
not use <code>@code</code> for the keystroke commands of GNU Emacs (use
<code>@kbd</code> instead) although you may use <code>@code</code> for the names
of the Emacs Lisp functions that the keystroke commands invoke.
</ul>
<p>Since <code>@command</code>, <code>@option</code>, and <code>@env</code> were
introduced relatively recently, it is acceptable to use <code>@code</code> or
<code>@samp</code> for command names, options, and environment variables.
The new commands allow you to express the markup more precisely, but
there is no real harm in using the older commands, and of course the
long-standing manuals do so.
<p>Ordinarily, TeX will consider breaking lines at ‘<samp><span class="samp">-</span></samp>’ and
‘<samp><span class="samp">_</span></samp>’ characters within <code>@code</code> and related commands. This
can be controlled with <code>@allowcodebreaks</code>
(see <a href="allowcodebreaks.html#allowcodebreaks"><code>@allowcodebreaks</code></a>).
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