While Loop

A while loop repeats as long as its condition remains true.

while_loop.c

#include <stdio.h>

int main(void) {
    int countdown = ;
    int sum = 0;

    while (countdown > 0) {
        sum += countdown;
        countdown--;
    }

    printf("sum=%d\n", sum);
    return 0;
}

#include <stdio.h>

int main(void) {
    int countdown = ;
    int sum = 0;

    while (countdown > 0) {
        sum += countdown;
        countdown--;
    }

    printf("sum=%d\n", sum);
    return 0;
}

#include <stdio.h>

int main(void) {
    int countdown = ;
    int sum = 0;

    while (countdown > 0) {
        sum += countdown;
        countdown--;
    }

    printf("sum=%d\n", sum);
    return 0;
}

while `while (condition)` checks before each iteration.

countdown Changing the loop variable moves the condition toward false.