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<h3 class="section">4.2 Conditional Syntax</h3>
<p><a name="index-g_t_0023if-84"></a>A conditional in the C preprocessor begins with a <dfn>conditional
directive</dfn>: &lsquo;<samp><span class="samp">#if</span></samp>&rsquo;, &lsquo;<samp><span class="samp">#ifdef</span></samp>&rsquo; or &lsquo;<samp><span class="samp">#ifndef</span></samp>&rsquo;.
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