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<h2><a name="memset" id="memset">memset</a></h2>
<div class="level2">

<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;">    <span class="co2">#include &lt;cstring&gt;</span>
    <span class="kw4">void</span><span class="sy0">*</span> memset<span class="br0">&#40;</span> <span class="kw4">void</span><span class="sy0">*</span> buffer<span class="sy0">,</span> <span class="kw4">int</span> ch<span class="sy0">,</span> size_t count <span class="br0">&#41;</span><span class="sy0">;</span></pre>
<p>
The function memset copies <code>ch</code> into the first <code>count</code> characters of <code>buffer</code>, and
returns <code>buffer</code>. memset is useful for intializing a section of memory to some
value. For example, this command:
</p>
<pre class="c code c++" style="font-family:monospace;">     <span class="kw4">const</span> <span class="kw4">int</span> ARRAY_LENGTH <span class="sy0">=</span> <span class="nu0">300</span><span class="sy0">;</span>
     <span class="kw4">char</span> the_array<span class="br0">&#91;</span>ARRAY_LENGTH<span class="br0">&#93;</span><span class="sy0">;</span>
     ...
     <span class="co1">// zero out the contents of the_array</span>
     memset<span class="br0">&#40;</span> the_array<span class="sy0">,</span> <span class="st0">'<span class="es5">\0</span>'</span><span class="sy0">,</span> ARRAY_LENGTH <span class="br0">&#41;</span><span class="sy0">;</span></pre>
<p>
…is a very efficient way to set all values of <code>the_array</code> to zero.
</p>

<p>
The table below compares two different methods for initializing an array of
characters: a for-loop versus memset. As the size of the data being
initialized increases, memset clearly gets the job done much more quickly:

</p>
<table class="inline">
	<tr class="row0">
		<th class="col0"> Input size </th><th class="col1"> Initialized with a for-loop </th><th class="col2"> Initialized with memset() </th>
	</tr>
	<tr class="row1">
		<td class="col0 leftalign"> 1000       </td><td class="col1 leftalign"> 0.016                       </td><td class="col2 leftalign"> 0.017                     </td>
	</tr>
	<tr class="row2">
		<td class="col0 leftalign"> 10000      </td><td class="col1 leftalign"> 0.055                       </td><td class="col2 leftalign"> 0.013                     </td>
	</tr>
	<tr class="row3">
		<td class="col0 leftalign"> 100000     </td><td class="col1 leftalign"> 0.443                       </td><td class="col2 leftalign"> 0.029                     </td>
	</tr>
	<tr class="row4">
		<td class="col0 leftalign"> 1000000    </td><td class="col1 leftalign"> 4.337                       </td><td class="col2 leftalign"> 0.291                     </td>
	</tr>
</table>

<p>
Related Topics: <a href="../../c/string/memcmp.html" class="wikilink1" title="c:string:memcmp">memcmp</a>, <a href="../../c/string/memcpy.html" class="wikilink1" title="c:string:memcpy">memcpy</a>, <a href="../../c/string/memmove.html" class="wikilink1" title="c:string:memmove">memmove</a>
</p>

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