Do–while loop in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple do–while loop

What is the output of this C code?

C

int main() {
    int i = 1;
    do {
        printf("%d ", i);
        i++;
    } while (i <= 3);
    return 0;
}

A 1 2 3

B 1 2

C No output

D 2 3

💡 Hint

Remember, do–while executes the loop body before checking the condition.

The loop starts with i=1, prints it, then increments i. It repeats while i <= 3, so it prints 1, 2, and 3.

❓ Predict Output

intermediate

Do–while loop with initial false condition

What will this program print?

C

int main() {
    int i = 5;
    do {
        printf("%d ", i);
        i++;
    } while (i < 5);
    return 0;
}

A 5 6

B No output

C Runtime error

D 5

💡 Hint

The loop body runs once before the condition is checked.

Even though i < 5 is false initially, the do–while loop runs the body once, printing 5.

❓ Predict Output

advanced

Nested do–while loops output

What is the output of this nested do–while loop code?

C

int main() {
    int i = 1, j;
    do {
        j = 1;
        do {
            printf("%d%d ", i, j);
            j++;
        } while (j <= 2);
        i++;
    } while (i <= 2);
    return 0;
}

A 11 21 12 22

B 11 12 21 22

C 12 11 22 21

D 11 12 22 21

💡 Hint

The inner loop runs fully for each iteration of the outer loop.

For i=1, j runs 1 to 2 printing 11 and 12. Then i=2, j runs 1 to 2 printing 21 and 22.

❓ Predict Output

advanced

Do–while loop with break statement

What will this program print?

C

int main() {
    int i = 1;
    do {
        if (i == 3) break;
        printf("%d ", i);
        i++;
    } while (i <= 5);
    return 0;
}

A 1 2 3

B 1 2 3 4 5

C 1 2

D No output

💡 Hint

The break stops the loop when i equals 3 before printing.

When i is 3, the loop breaks before printing, so only 1 and 2 are printed.

❓ Predict Output

expert

Value of variable after do–while loop with complex condition

What is the value of variable x after this code runs?

C

int main() {
    int x = 0, y = 5;
    do {
        x += y;
        y--;
    } while (y > 0);
    printf("%d", x);
    return 0;
}

A 15

B 10

C 5

D 0

💡 Hint

Sum y from 5 down to 1 added to x.

The loop adds 5 + 4 + 3 + 2 + 1 = 15 to x before y becomes 0 and loop stops.