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<h3 class="section">A.1 @-Command Syntax</h3>

<p><a name="index-g_t_0040_0040_002dcommand-syntax-1390"></a><a name="index-Syntax_002c-of-_0040_0040_002dcommands-1391"></a><a name="index-Command-syntax-1392"></a>
The character &lsquo;<samp><span class="samp">@</span></samp>&rsquo; is used to start special Texinfo commands. 
(It has the same meaning that &lsquo;<samp><span class="samp">\</span></samp>&rsquo; has in plain TeX.)  Texinfo
has four types of @-command:

     <dl>
<dt>1. Non-alphabetic commands.<dd>These commands consist of an @ followed by a punctuation mark or
other character that is not part of the alphabet.  Non-alphabetic
commands are almost always part of the text within a paragraph.  The
non-alphabetic commands include <code>@@</code>, <code>@{</code>, <code>@}</code>,
<code>@.</code>, <code>@</code><kbd>SPACE</kbd>, most of the accent commands, and
many more.

     <br><dt>2. Alphabetic commands that do not require arguments.<dd>These commands start with @ followed by a word followed by left- and
right-hand braces.  These commands insert special symbols in the
document; they do not require arguments.  For example,
<code>@dots{}</code> &rArr; &lsquo;<samp><span class="samp">...</span></samp>&rsquo;, <code>@equiv{}</code>
&rArr; &lsquo;<samp><span class="samp">==</span></samp>&rsquo;, <code>@TeX{}</code> &rArr; `TeX',
and <code>@bullet{}</code> &rArr; &lsquo;<samp><span class="samp">&bull;</span></samp>&rsquo;.

     <br><dt>3. Alphabetic commands that require arguments within braces.<dd>These commands start with @ followed by a letter or a word, followed by an
argument within braces.  For example, the command <code>@dfn</code> indicates
the introductory or defining use of a term; it is used as follows: &lsquo;<samp><span class="samp">In
Texinfo, @@-commands are @dfn{mark-up} commands.</span></samp>&rsquo;

     <br><dt>4. Alphabetic commands that occupy an entire line.<dd>These commands occupy an entire line.  The line starts with @,
followed by the name of the command (a word); for example, <code>@center</code>
or <code>@cindex</code>.  If no argument is needed, the word is followed by
the end of the line.  If there is an argument, it is separated from
the command name by a space.  Braces are not used. 
</dl>

  <p><a name="index-Braces-and-argument-syntax-1393"></a>Thus, the alphabetic commands fall into classes that have
different argument syntaxes.  You cannot tell to which class a command
belongs by the appearance of its name, but you can tell by the
command's meaning: if the command stands for a glyph, it is in
class 2 and does not require an argument; if it makes sense to use the
command together with other text as part of a paragraph, the command
is in class 3 and must be followed by an argument in braces;
otherwise, it is in class 4 and uses the rest of the line as its
argument.

  <p>The purpose of having a different syntax for commands of classes 3 and
4 is to make Texinfo files easier to read, and also to help the GNU
Emacs paragraph and filling commands work properly.  There is only one
exception to this rule: the command <code>@refill</code>, which is always
used at the end of a paragraph immediately following the final period
or other punctuation character.  <code>@refill</code> takes no argument and
does <em>not</em> require braces.  <code>@refill</code> never confuses the
Emacs paragraph commands because it cannot appear at the beginning of
a line.  It is also no longer needed, since all formatters now refill
paragraphs automatically.

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