for
statement and its general form is
for( expression 1; expression 2; expression 3 ) statementThe operation of this statement is illustrated in this flow chart.
From the flow chart, we can see that the statement is equivalent to a while that's set up like this:
expression 1 ; while( expression 2 ) { statement expression 3 ; }(This equivalence is almost exact. The
for
and the "equivalent" while
will
behave differently under the continue
statement that
we'll see a little later.)
By way of example, we could print out the numbers from 0 to 9
using a for
statement like this:
for( i = 0; i < 10; i++ ) printf( "%d\n", i ) ;And like with the other statements, we can group multiple statements in the body of the loop by enclosing them in braces (
{}
).
The for
is much like the counted loop statement
discussed earlier, but it is more
flexible.
Instead of just counting by one, we can do any form of updating we
want in expression 3.
For example, to print out just the even numbers we could do something
like this:
for( i = 0; i < 10; i += 2 ) printf( "%d\n", i ) ;Write a
for
statement which counts the variable x
down from 10 to (but not including) 0.