title: Why are the fast integer types faster than the other integer types?
body: <p>In ISO/IEC 9899:2018 (C18), it is stated under 7.20.1.3:</p>
  
  <blockquote>
    <p>7.20.1.3 Fastest minimum-width integer types</p>
    
    <p>1 Each of the following types designates an integer type that is usually fastest<sup>268)</sup> to operate with among all integer types that have at least the specified width.</p>
    
    <p>2 The typedef name <code>int_fastN_t</code> designates the fastest signed integer type with a width of at least N. The typedef name <code>uint_fastN_t</code> designates the fastest unsigned integer type with a width of at least N.</p>
    
    <p>3 The following types are required:</p>
    
    <p><code>int_fast8_t</code>, <code>int_fast16_t</code>, <code>int_fast32_t</code>, <code>int_fast64_t</code>,
    <code>uint_fast8_t</code>, <code>uint_fast16_t</code>, <code>uint_fast32_t</code>, <code>uint_fast64_t</code></p>
    
    <p>All other types of this form are optional.</p>
    
    <hr>
    
    <p><sup>268)</sup> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear grounds for choosing one type over another, it will simply pick some integer type satisfying the signedness and width requirements.</p>
  </blockquote>
  
  <hr>
  
  <p>But it is not stated why these "fast" integer types are faster.</p>
  
  <ul>
  <li>Why are these fast integer types faster than the other integer types?
  
  <hr></li>
  </ul>
  
  <p><sub>I tagged the question with C++, because the fast integer types are also available in C++17 in the header file of <code>cstdint</code>. Unfortunately, in ISO/IEC 14882:2017 (C++17) there is no such section about their explanation; I had implemented that section otherwise in the question´s body.</sub></p>
  
  <hr>
  
  <p>Information: In C, they are declared in the header file of <code>stdint.h</code>.</p>