Sams Teach Yourself C in 21 Days

Basic Program Control 135

6

You might have noticed that a whilestatement is essentially a forstatement without the

initialization and increment components. Thus,

for ( ; condition; )

is equivalent to

while (condition)

Because of this equality, anything that can be done with a forstatement can also be done

with a whilestatement. When you use a whilestatement, any necessary initialization

must first be performed in a separate statement, and the updating must be performed by a

statement that is part of the whileloop.

When initialization and updating are required, most experienced C programmers prefer

to use a forstatement rather than a whilestatement. This preference is based primarily

on source code readability. When you use a forstatement, the initialization, test, and

increment expressions are located together and are easy to find and modify. With a while

statement, the initialization and update expressions are located separately and might be

less obvious.

ThewhileStatement

while (condition)

statement(s)

conditionis any valid C expression, usually a relational expression. When condition

evaluates to false (zero), the whilestatement terminates, and execution passes to the first

statement following statement(s); otherwise, the first C statement in statement(s)is

executed.

statement(s)is the C statement(s) that is executed as long as conditionremains true.

Awhilestatement is a C looping statement. It allows repeated execution of a statement

or block of statements as long as the condition remains true (nonzero). If the condition is

not true when the whilecommand is first executed, the statement(s)is never executed.

Example 1

int x = 0;

while (x < 10)

{

printf(“\nThe value of x is %d”, x );

x++;

}

,

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YNTAX

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