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<a name="C-Constants"></a>
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<a name="C-and-C_002b_002b-Constants"></a>
<h4 class="subsubsection">15.4.1.2 C and C<tt>++</tt> Constants</h4>

<a name="index-C-and-C_002b_002b-constants"></a>

<p><small>GDB</small> allows you to express the constants of C and C<tt>++</tt> in the
following ways:
</p>
<ul>
<li> Integer constants are a sequence of digits.  Octal constants are
specified by a leading &lsquo;<samp>0</samp>&rsquo; (i.e. zero), and hexadecimal constants
by a leading &lsquo;<samp>0x</samp>&rsquo; or &lsquo;<samp>0X</samp>&rsquo;.  Constants may also end with a letter
&lsquo;<samp>l</samp>&rsquo;, specifying that the constant should be treated as a
<code>long</code> value.

</li><li> Floating point constants are a sequence of digits, followed by a decimal
point, followed by a sequence of digits, and optionally followed by an
exponent.  An exponent is of the form:
&lsquo;<samp>e<span class="roman">[[</span>+<span class="roman">]|</span><span class="nolinebreak">-</span><span class="roman">]</span><var>nnn</var><!-- /@w --></samp>&rsquo;, where <var>nnn</var> is another
sequence of digits.  The &lsquo;<samp>+</samp>&rsquo; is optional for positive exponents.
A floating-point constant may also end with a letter &lsquo;<samp>f</samp>&rsquo; or
&lsquo;<samp>F</samp>&rsquo;, specifying that the constant should be treated as being of
the <code>float</code> (as opposed to the default <code>double</code>) type; or with
a letter &lsquo;<samp>l</samp>&rsquo; or &lsquo;<samp>L</samp>&rsquo;, which specifies a <code>long double</code>
constant.

</li><li> Enumerated constants consist of enumerated identifiers, or their
integral equivalents.

</li><li> Character constants are a single character surrounded by single quotes
(<code>'</code>), or a number&mdash;the ordinal value of the corresponding character
(usually its <small>ASCII</small> value).  Within quotes, the single character may
be represented by a letter or by <em>escape sequences</em>, which are of
the form &lsquo;<samp>\<var>nnn</var></samp>&rsquo;, where <var>nnn</var> is the octal representation
of the character&rsquo;s ordinal value; or of the form &lsquo;<samp>\<var>x</var></samp>&rsquo;, where
&lsquo;<samp><var>x</var></samp>&rsquo; is a predefined special character&mdash;for example,
&lsquo;<samp>\n</samp>&rsquo; for newline.

<p>Wide character constants can be written by prefixing a character
constant with &lsquo;<samp>L</samp>&rsquo;, as in C.  For example, &lsquo;<samp>L'x'</samp>&rsquo; is the wide
form of &lsquo;<samp>x</samp>&rsquo;.  The target wide character set is used when
computing the value of this constant (see <a href="Character-Sets.html#Character-Sets">Character Sets</a>).
</p>
</li><li> String constants are a sequence of character constants surrounded by
double quotes (<code>&quot;</code>).  Any valid character constant (as described
above) may appear.  Double quotes within the string must be preceded by
a backslash, so for instance &lsquo;<samp>&quot;a\&quot;b'c&quot;</samp>&rsquo; is a string of five
characters.

<p>Wide string constants can be written by prefixing a string constant
with &lsquo;<samp>L</samp>&rsquo;, as in C.  The target wide character set is used when
computing the value of this constant (see <a href="Character-Sets.html#Character-Sets">Character Sets</a>).
</p>
</li><li> Pointer constants are an integral value.  You can also write pointers
to constants using the C operator &lsquo;<samp>&amp;</samp>&rsquo;.

</li><li> Array constants are comma-separated lists surrounded by braces &lsquo;<samp>{</samp>&rsquo;
and &lsquo;<samp>}</samp>&rsquo;; for example, &lsquo;<samp>{1,2,3}</samp>&rsquo; is a three-element array of
integers, &lsquo;<samp>{{1,2}, {3,4}, {5,6}}</samp>&rsquo; is a three-by-two array,
and &lsquo;<samp>{&amp;&quot;hi&quot;, &amp;&quot;there&quot;, &amp;&quot;fred&quot;}</samp>&rsquo; is a three-element array of pointers.
</li></ul>

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