While Loops

While loops are similar to for loops, but have less functionality. A while loop continues executing the while block as long as the condition in the while remains true. For example, the following code will execute exactly ten times:

    int n = 0;
    while (n < 10) {
        n++;
    }

While loops can also execute infinitely if a condition is given which always evaluates as true (non-zero):

    while (1) {
        /* do something */
    }

Loop Directives

There are two important loop directives that are used in conjunction with all loop types in C - the break and continue directives.

The break directive halts a loop after ten loops, even though the while loop never finishes:

    int n = 0;
    while (1) {
        n++;
        if (n == 10) {
            break;
        }
    }


                            

In the following code, the continue directive causes the printf command to be skipped, so that only even numbers are printed out:

    int n = 0;
    while (n < 10) {
        n++;
    
        /* check that n is odd */
        if (n % 2 == 1) {
            /* go back to the start of the while block */
            continue;
        }
    
        /* we reach this code only if n is even */
        printf("The number %d is even.\n", n);
    }


                            