octal_digit   = "0" … "7" .
hex_digit     = "0" … "9" | "A" … "F" | "a" … "f" .
</pre>

<h2 id="Lexical_elements">Lexical elements</h2>

<h3 id="Comments">Comments</h3>

<p>
Comments serve as program documentation. There are two forms:
</p>

<ol>
<li>
<i>Line comments</i> start with the character sequence <code>//</code>
and stop at the end of the line.
</li>
<li>