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<title>
C Guide--1.6 Statements
</title>
<!-- Changed by: eric huss, 12-Mar-1997 -->
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1.5 Operators</a></td>
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<hr>
<a name="if"></a>
<h1>1.6.1 if</h1>
<p>
The if statement evaluates an expression. If that expression is true, then a statement is
executed. If an else clause is given and if the expression is false, then the else's statement is
executed.
<p>
Syntax:<br>
<blockquote>
<code><b>if(</b></code> <i>expression</i> <code><b>)</b></code> <i>statement1</i><code><b>;</b></code><br>
<br>
<i>or</i><br>
<br>
<code><b>if(</b></code> <i>expression</i> <code><b>)</b></code> <i>statement1</i><code><b>;</b></code><br>
<code><b>else</b></code> <i>statement2</i> <code><b>;</b></code><br>
</blockquote>
<br>
Examples:<br>
<blockquote><code><b><pre>
if(loop&lt;3) counter++;
if(x==y)
x++;
else
y++;
if(z&gt;x)
{
z=5;
x=3;
}
else
{
z=3;
x=5;
}
</pre></b></code></blockquote>
<a name="switch"></a>
<h1> 1.6.2 switch</h1>
<p>
A switch statement allows a single variable to be compared with several possible
constants. If the variable matches one of the constants, then a execution jump is made to that
point. A constant can not appear more than once, and there can only be one default expression.<br>
<br>
Syntax:<br>
<blockquote><pre>
<code><b>switch (</b></code> <i>variable</i><code><b> )
{
case </b></code><i>const</i><code><b>:</b></code>
<i>statements...</i><code><b>;
default:
</b></code><i>statements...</i><code><b>;
}
</b></code>
</pre></blockquote>
Examples:<br>
<blockquote><code><b><pre>
switch(betty)
{
case 1:
printf("betty=1\n");
case 2:
printf("betty=2\n");
break;
case 3:
printf("betty=3\n");
break;
default:
printf("Not sure.\n");
}
</pre></b></code></blockquote>
If betty is 1, then two lines are printed: betty=1 and betty=2. If betty is 2, then only one line is
printed: betty=2. If betty=3, then only one line is printed: betty=3. If betty does not equal 1, 2,
or 3, then "Not sure." is printed.
<br>
<a name="while"></a>
<h1> 1.6.3 while</h1>
<p>
The while statement provides an iterative loop.
<br>
Syntax:<br>
<blockquote>
<code><b>while(</b></code> <i> expression</i> <code><b>)</b></code> <i> statement...</i>
</blockquote>
<i>statement</i> is executed repeatedly as long as <i>expression</i> is true. The test on <i>expression</i>
takes place before each execution of <i>statement</i>.
<br>
Examples:<br>
<blockquote><code><b><pre>
while(*pointer!='j') pointer++;
while(counter&lt;5)
{
printf("counter=%i",counter);
counter++;
}
</pre></b></code></blockquote>
<br>
<a name="do"></a>
<h1> 1.6.4 do</h1>
<br>
The do...while construct provides an iterative loop.<br>
<br>
Syntax:<br>
<blockquote>
<code><b>do</code></b> <i>statement...</i> <code><b>while(</code></b> <i>expression</i> <code><b>);</code></b>
</blockquote>
<i>statement</i> is executed repeatedly as long as <i>expression</i> is true. The test on <i>expression</i>
takes place after each execution of <i>statement</i>.<br>
<br>
Examples:<br>
<blockquote><code><b><pre>
do {
betty++;
printf("%i",betty);
} while (betty&lt;100);
</pre></b></code></blockquote>
<a name="for"></a>
<h1> 1.6.5 for</h1>
<p>
The for statement allows for a controlled loop.
<p>
Syntax:
<blockquote>
<code><b>for(</b></code> <i>expression1</i> ; <i>expression2</i> ; <i>expression3</i><code><b> )</b></code> <i>statement...</i>
</blockquote>
<i>expression1</i> is evaluated before the first iteration. After each iteration, <i>expression3</i> is
evaluated. Both <i>expression1</i> and <i>expression3</i> may be ommited. If <i>expression2</i> is ommited, it is
assumed to be 1. <i>statement</i> is executed repeatedly until the value of <i>expression2</i> is 0. The test
on <i>expression2</i> occurs before each execution of <i>statement</i>.
<p>
Examples:
<blockquote>
<code><b><pre>
for(loop=0;loop&lt;1000;loop++)
printf("%i\n",loop);
</pre></b></code>
</blockquote>
Prints numbers 0 through 999.
<blockquote>
<code><b><pre>
for(x=3, y=5; x&lt;100+y; x++, y--)
{
printf("%i\n",x);
some_function();
}
</pre></b></code>
</blockquote>
Prints numbers 3 through 53. some_function is called 51 times.
<br>
<a name="goto"></a>
<h1> 1.6.6 goto</h1>
<p>
The goto statement transfers program execution to some label within the program.
<p>
Syntax:
<blockquote>
<code><b>goto</b></code><i> label</i><code><b>;</b></code><br>
....<br>
<i>label</i><code><b>:</b></code><br>
</blockquote>
Examples:
<blockquote><code><b><pre>
goto skip_point;
printf("This part was skipped.\n");
skip_point:
printf("Hi there!\n");
</pre></b></code>
</blockquote>
Only the text "Hi there!" is printed.
<br>
<a name="continue"></a>
<h1> 1.6.7 continue</h1>
<p>
The continue statement can only appear in a loop body. It causes the rest of the
statement body in the loop to be skipped.
<p>
Syntax:
<blockquote><code><b>
continue;
</b></code></blockquote>
Examples:
<blockquote><code><b><pre>
for(loop=0;loop&lt;100;loop++)
{
if(loop==50)
continue;
printf("%i\n",loop);
}
</pre></b></code>
</blockquote>
The numbers 0 through 99 are printed except for 50.
<blockquote>
<code><b><pre>
joe=0;
while(joe&lt;1000)
{
for(zip=0;zip&lt;100;zip++)
{
if(joe==500)
continue;
printf("%i\n",joe);
}
joe++;
}
</pre></b></code>
</blockquote>
Each number from 0 to 999 is printed 100 times except for the number 500 which is not printed
at all.
<a name="break"></a>
<h1> 1.6.8 break</h1>
<p>
The break statement can only appear in a switch body or a loop body. It causes the
execution of the current enclosing switch or loop body to terminate.
<p>
Syntax:
<blockquote><code><b>
break;
</b></code></blockquote>
Examples:
<blockquote><code><b><pre>
switch(henry)
{
case 1: print("Hi!\n");
break;
case 2: break;
}
</pre></b></code></blockquote>
If henry is equal to 2, nothing happens.
<blockquote><code><b><pre>
for(loop=0;loop&lt;50;loop++)
{
if(loop==10)
break;
printf("%i\n",loop);
}
</pre></b></code></blockquote>
Only numbers 0 through 9 are printed.
<a name="return"></a>
<h1> 1.6.9 return</h1>
<p>
The return statement causes the current function to terminate. It can return a value to the
calling function. A return statement can not appear in a function whose return type is void. If
the value returned has a type different from that of the function's return type, then the value is
converted. Using the return statement without an expression creates an undefined result.
Reaching the } at the end of the function is the same as returning without an expression.
<p>
Syntax:
<blockquote><code><b>
return</b></code> <i> expression</i><code><b>;</b></code>
</blockquote>
Examples:
<blockquote><code><b><pre>
int alice(int x, int y)
{
if(x&lt;y)
return(1);
else
return(0);
}
</pre></b></code></blockquote>
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