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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head> <meta name="generator" content= "HTML Tidy for Linux/x86 (vers 1 September 2005), see www.w3.org"> <title>memset</title> <link href="../cppreference.css" rel="stylesheet" type="text/css"></head><body><table> <tr> <td> <div class="body-content"> <div class="header-box"> <a href="../index.html">cppreference.com</a> > <a href= "index.html">Standard C String and Character</a> > <a href= "memset.html">memset</a> </div> <div class="name-format"> memset </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <string.h> void* memset( void* buffer, int ch, size_t count );</pre> <p>The function memset() copies <em>ch</em> into the first <em>count</em> characters of <em>buffer</em>, and returns <em>buffer</em>. memset() is useful for intializing a section of memory to some value. For example, this command:</p> <pre class="example-code"> memset( the_array, '\0', sizeof(the_array) ); </pre> <p>...is a very efficient way to set all values of the_array 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="misc-table"> <tr class="misc-table-tr-1"> <th>Input size</th> <th>Initialized with a for-loop</th> <th>Initialized with memset()</th> </tr> <tr class="misc-table-tr-2"> <td>1000</td> <td>0.016</td> <td>0.017</td> </tr> <tr class="misc-table-tr-1"> <td>10000</td> <td>0.055</td> <td>0.013</td> </tr> <tr class="misc-table-tr-2"> <td>100000</td> <td>0.443</td> <td>0.029</td> </tr> <tr class="misc-table-tr-1"> <td>1000000</td> <td>4.337</td> <td>0.291</td> </tr> </table> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="memcmp.html">memcmp</a><br> <a href="memcpy.html">memcpy</a><br> <a href="memmove.html">memmove</a> </div> </div> </td> </tr> </table></body></html>⌨️ 快捷键说明
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