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| 22 | <title>Increment/Decrement (GNU C Language Manual)</title>
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| 23 |
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| 24 | <meta name="description" content="Increment/Decrement (GNU C Language Manual)">
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| 30 | <link href="Symbol-Index.html" rel="index" title="Symbol Index">
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| 31 | <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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| 32 | <link href="Assignment-Expressions.html" rel="up" title="Assignment Expressions">
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| 33 | <link href="Postincrement_002fPostdecrement.html" rel="next" title="Postincrement/Postdecrement">
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| 55 | </head>
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| 56 |
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| 57 | <body lang="en">
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| 58 | <span id="Increment_002fDecrement"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Postincrement_002fPostdecrement.html" accesskey="n" rel="next">Postincrement/Postdecrement</a>, Previous: <a href="Modifying-Assignment.html" accesskey="p" rel="prev">Modifying Assignment</a>, Up: <a href="Assignment-Expressions.html" accesskey="u" rel="up">Assignment Expressions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Index.html" title="Index" rel="index">Index</a>]</p>
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| 61 | </div>
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| 62 | <hr>
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| 63 | <span id="Increment-and-Decrement-Operators"></span><h3 class="section">7.4 Increment and Decrement Operators</h3>
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| 64 | <span id="index-increment-operator"></span>
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| 65 | <span id="index-decrement-operator"></span>
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| 66 | <span id="index-operator_002c-increment"></span>
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| 67 | <span id="index-operator_002c-decrement"></span>
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| 68 | <span id="index-preincrement-expression"></span>
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| 69 | <span id="index-predecrement-expression"></span>
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| 70 |
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| 71 | <p>The operators ‘<samp>++</samp>’ and ‘<samp>--</samp>’ are the <em>increment</em> and
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| 72 | <em>decrement</em> operators. When used on a numeric value, they add or
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| 73 | subtract 1. We don’t consider them assignments, but they are
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| 74 | equivalent to assignments.
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| 75 | </p>
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| 76 | <p>Using ‘<samp>++</samp>’ or ‘<samp>--</samp>’ as a prefix, before an lvalue, is called
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| 77 | <em>preincrement</em> or <em>predecrement</em>. This adds or subtracts 1
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| 78 | and the result becomes the expression’s value. For instance,
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| 79 | </p>
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| 80 | <div class="example">
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| 81 | <pre class="example">#include <stdio.h> /* <span class="roman">Declares <code>printf</code>.</span> */
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| 82 |
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| 83 | int
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| 84 | main (void)
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| 85 | {
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| 86 | int i = 5;
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| 87 | printf ("%d\n", i);
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| 88 | printf ("%d\n", ++i);
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| 89 | printf ("%d\n", i);
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| 90 | return 0;
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| 91 | }
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| 92 | </pre></div>
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| 93 |
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| 94 | <p>prints lines containing 5, 6, and 6 again. The expression <code>++i</code>
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| 95 | increments <code>i</code> from 5 to 6, and has the value 6, so the output
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| 96 | from <code>printf</code> on that line says ‘<samp>6</samp>’.
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| 97 | </p>
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| 98 | <p>Using ‘<samp>--</samp>’ instead, for predecrement,
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| 99 | </p>
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| 100 | <div class="example">
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| 101 | <pre class="example">#include <stdio.h> /* <span class="roman">Declares <code>printf</code>.</span> */
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| 102 |
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| 103 | int
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| 104 | main (void)
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| 105 | {
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| 106 | int i = 5;
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| 107 | printf ("%d\n", i);
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| 108 | printf ("%d\n", --i);
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| 109 | printf ("%d\n", i);
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| 110 | return 0;
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| 111 | }
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| 112 | </pre></div>
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| 113 |
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| 114 | <p>prints three lines that contain (respectively) ‘<samp>5</samp>’, ‘<samp>4</samp>’, and
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| 115 | again ‘<samp>4</samp>’.
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| 116 | </p>
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| 117 |
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| 118 |
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| 119 |
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| 120 | </body>
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| 121 | </html>
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