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   9 <title>2.6 Assignment Operators</title>
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  15 <H2>2.6 Assignment Operators</H2>
  16
  17 <p>[This section corresponds to K&amp;R Sec. 2.10]
  18 </p><p>The assignment operator <TT>=</TT> assigns a value to a variable.
  19 For example,
  20 <pre>
  21         x = 1
  22 </pre>
  23 sets <TT>x</TT> to 1,
  24 and
  25 <pre>
  26         a = b
  27 </pre>
  28 sets <TT>a</TT> to whatever <TT>b</TT>'s value is.
  29 The expression
  30 <pre>
  31         i = i + 1
  32 </pre>
  33 is, as we've mentioned elsewhere, the standard programming
  34 idiom for increasing a variable's value by 1:
  35 this expression takes <TT>i</TT>'s old value, adds 1 to it,
  36 and stores it back into <TT>i</TT>.
  37 (C provides several ``shortcut'' operators for
  38 modifying variables in this and similar ways, which we'll meet
  39 later.)
  40 </p><p>We've called the <TT>=</TT> sign the ``assignment operator''
  41 and referred to ``assignment expressions''
  42 because, in fact, <TT>=</TT> <em>is</em> an operator just like
  43 <TT>+</TT> or <TT>-</TT>.
  44 C does not have ``assignment statements'';
  45 instead,
  46 an assignment like <TT>a = b</TT> is an expression
  47 and can be used wherever any expression can appear.
  48 Since it's an expression,
  49 the assignment <TT>a = b</TT> has a value,
  50 namely, the same value that's assigned to <TT>a</TT>.
  51 This value can then be used in a larger expression;
  52 for example,
  53 we might write
  54 <pre>
  55         c = a = b
  56 </pre>
  57 which is equivalent to
  58 <pre>
  59         c = (a = b)
  60 </pre>
  61 and assigns <TT>b</TT>'s value to both <TT>a</TT> and <TT>c</TT>.
  62 (The assignment operator, therefore, groups from right to left.)
  63 Later we'll see other circumstances
  64 in which it can be useful to use the value of an assignment expression.
  65 </p><p>It's usually a matter of style whether you initialize a
  66 variable with an initializer in its declaration or with an
  67 assignment expression near where you first use it.
  68 That is,
  69 there's no particular difference between
  70 <pre>
  71         int a = 10;
  72 </pre>
  73 and
  74 <pre>
  75         int a;
  76
  77         /* later... */
  78
  79         a = 10;
  80 </pre>
  81 </p><hr>
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  90 This page by <a href="http://www.eskimo.com/~scs/">Steve Summit</a>
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