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<title>The WHILE keyword.</title>
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<center><h1>The WHILE keyword.</h1></center>
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The <b>while</b> keyword is related to <a href=do.html>do</a>
and <a href=for.html>for</a>. Its purpose is to repeatedly execute
a <a href="statements.html#blocks">block</a> of statements. Here is
an example :
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<pre>
main()
{
int i=5;
while(--i)
{
printf(" i is %d\n", i);
}
}
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The expression <b>i--</b> is evaluated and if its
<a href="../CONCEPT/true_false.html">true</a> the statements in the
<a href="statements.html#blocks">block</a> are executed.
The loop continues until the expression is false (zero).
The result will look like this:
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i is 4
i is 3
i is 2
i is 1
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It is important to note that the statements
on a <b>while</b> will not get executed if the first evaluation of the
expression is FALSE. If you do not want this to happen you may prefer
to use the <a href="do.html">do</a> statement.
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<p>
Now consider the next example.
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<pre>
main()
{
int i=5;
while(--i);
{
printf(" i is %d\n", i);
}
}
</pre>
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The result will look like this:
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i is 0
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This is because of the <b>;</b> on the end of the <b>while</b>
statement which means the <b>while</b> will loop (executing NULL statements)
until <b>i</b> is zero. Execution will then continue down the program
(to the printf).
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<h2>Examples:</h2>
<img src="../../GRAPHICS/computer.gif" align=left alt="o">
<a href="../EXAMPLES/while.c">Basic <b>while</b></a>.
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<h2>See also:</h2>
<ul>
<li><a href="while.html">for</a> keyword.
<li><a href="do.html">do</a> keyword.
<li><a href="break.html">break</a> keyword.
<li><a href="continue.html">continue</a> keyword.
</ul>
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<hr>
<address>Martin Leslie
</address><p>
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