Both while and do-while loops repeat a block of code while a condition remains true. The main difference is when the condition is evaluated.

#include <stdio.h>

int main()
{
    int i = 6;

    while (i <= 5)
    {
        printf("while: %d\n", i);
    }

    do
    {
        printf("do-while: %d\n", i);
    }
    while (i <= 5);

    return 0;
}

Example Output #

do-while: 6

Explanation #

The while loop evaluates its condition before executing the body:

while (i <= 5)

Since i is 6, the condition is false and the loop body does not execute.

The do-while loop evaluates its condition after executing the body:

do
{
    printf("do-while: %d\n", i);
}
while (i <= 5);

Therefore, its body executes once even though i <= 5 is false.