For loop
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In most imperative computer programming languages, a for loop is a control structure which allows code to be executed iteratively. For loops, unlike while loops, are typically used when the number of iterations is known before entering the loop.
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Examples
These for loops will calculate the factorial of a number:
QBasic or Visual Basic
Dim factorial As Long : factorial = 1 Dim counter As Integer For counter = 1 To 5 factorial = factorial * counter Next Print factorial
C or C++
unsigned long factorial = 1;
for (unsigned int counter = 1; counter <= 5; counter++)
factorial *= counter;
printf("%i", factorial);
Python
factorial = 1 for counter in xrange(1, 5): factorial *= counter print factorial
Java
long factorial = 1; for (int counter = 1; counter <= 5; counter++) factorial *= counter; System.out.println(factorial);
JavaScript
var factorial = 1; for (var counter = 1; counter <= 5; counter++) factorial *= counter; document.write(factorial);
Perl
my $factorial = 1;
for ( my $counter = 1; $counter <= 5; $counter++ ) {
$factorial *= $counter;
}
print $factorial;
A for loop can always be converted into a while loop.