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

<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;">    <span class="co2">#include &lt;cstdlib&gt;</span>
    <span class="kw4">int</span> atoi<span class="br0">&#40;</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy0">*</span>str <span class="br0">&#41;</span><span class="sy0">;</span></pre>
<p>
The atoi function converts <code>str</code> into an integer, and returns that integer. <code>str</code>
should start with whitespace or some sort of number, and atoi will stop
reading from <code>str</code> as soon as a non-numerical character has been read. For
example:
</p>
<pre class="c code c++" style="font-family:monospace;">    <span class="kw4">int</span> i<span class="sy0">;</span>
    i <span class="sy0">=</span> atoi<span class="br0">&#40;</span> <span class="st0">&quot;512&quot;</span> <span class="br0">&#41;</span><span class="sy0">;</span>
    i <span class="sy0">=</span> atoi<span class="br0">&#40;</span> <span class="st0">&quot;512.035&quot;</span> <span class="br0">&#41;</span><span class="sy0">;</span>
    i <span class="sy0">=</span> atoi<span class="br0">&#40;</span> <span class="st0">&quot;   512.035&quot;</span> <span class="br0">&#41;</span><span class="sy0">;</span>
    i <span class="sy0">=</span> atoi<span class="br0">&#40;</span> <span class="st0">&quot;   512+34&quot;</span> <span class="br0">&#41;</span><span class="sy0">;</span>
    i <span class="sy0">=</span> atoi<span class="br0">&#40;</span> <span class="st0">&quot;   512 bottles of beer on the wall&quot;</span> <span class="br0">&#41;</span><span class="sy0">;</span></pre>
<p>
All five of the above assignments to the variable <code>i</code> would result in it being
set to 512.
</p>

<p>
If the conversion cannot be performed, then atoi will return zero:
</p>
<pre class="c code c++" style="font-family:monospace;">    <span class="kw4">int</span> i <span class="sy0">=</span> atoi<span class="br0">&#40;</span> <span class="st0">&quot; does not work: 512&quot;</span> <span class="br0">&#41;</span><span class="sy0">;</span>  <span class="co1">// results in i == 0</span></pre>
<p>
You can use <a href="../../c/io/sprintf.html" class="wikilink1" title="c:io:sprintf">sprintf</a> to convert a number into a string.
</p>

<p>
Related Topics: <a href="../../c/string/atof.html" class="wikilink1" title="c:string:atof">atof</a>, <a href="../../c/string/atol.html" class="wikilink1" title="c:string:atol">atol</a>, <a href="../../c/io/sprintf.html" class="wikilink1" title="c:io:sprintf">sprintf</a>
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