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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>sizeof</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> &gt; <a href=    "index.html">C/C++ Keywords</a> &gt; <a href=    "sizeof.html">sizeof</a>  </div>  <div class="name-format">    sizeof  </div>  <p>The sizeof operator is a compile-time operator that returns the  size, in bytes, of the argument passed to it.  For example, the  following code uses sizeof to display the sizes of a number of  variables:</p>  <pre class="example-code">  struct EmployeeRecord {    int ID;    int age;    double salary;    EmployeeRecord* boss;  };  ...  cout &lt;&lt; "sizeof(int): " &lt;&lt; sizeof(int) &lt;&lt; endl       &lt;&lt; "sizeof(float): " &lt;&lt; sizeof(float) &lt;&lt; endl       &lt;&lt; "sizeof(double): " &lt;&lt; sizeof(double) &lt;&lt; endl       &lt;&lt; "sizeof(char): " &lt;&lt; sizeof(char) &lt;&lt; endl       &lt;&lt; "sizeof(EmployeeRecord): " &lt;&lt; sizeof(EmployeeRecord) &lt;&lt; endl;  int i;  float f;  double d;  char c;  EmployeeRecord er;  cout &lt;&lt; "sizeof(i): " &lt;&lt; sizeof(i) &lt;&lt; endl       &lt;&lt; "sizeof(f): " &lt;&lt; sizeof(f) &lt;&lt; endl       &lt;&lt; "sizeof(d): " &lt;&lt; sizeof(d) &lt;&lt; endl       &lt;&lt; "sizeof(c): " &lt;&lt; sizeof(c) &lt;&lt; endl       &lt;&lt; "sizeof(er): " &lt;&lt; sizeof(er) &lt;&lt; endl;</pre>  <p>When run, the above code displays this output:</p>  <pre class="example-code">  sizeof(int): 4  sizeof(float): 4  sizeof(double): 8  sizeof(char): 1  sizeof(EmployeeRecord): 20  sizeof(i): 4  sizeof(f): 4  sizeof(d): 8  sizeof(c): 1  sizeof(er): 20</pre>  <p>Note that sizeof can either take a variable type (such as  <strong>int</strong>) or a variable name (such as <strong>i</strong>  in the example above).</p>  <p>It is also important to note that the sizes of various types of  variables can change depending on what system you're on.  Check out  <a href="../data_types.html">a description  of the C and C++ data types</a> for more information.</p>  <p>The parentheses around the argument are not required if you are  using sizeof with a variable type (e.g. sizeof(int)).</p>  <div class="related-name-format">    Related topics:  </div>  <div class="related-content">    <a href="../data_types.html">C/C++ Data Types</a>  </div>  </div>  </td>    </tr>  </table></body></html>
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