While loop in C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a while loop in C++?

A while loop repeats a block of code as long as a given condition is true. It checks the condition before running the code each time.

beginner

What happens if the condition in a while loop is false at the start?

The code inside the while loop does not run even once if the condition is false at the beginning.

intermediate

How do you stop an infinite while loop?

You stop an infinite while loop by making sure the condition eventually becomes false, usually by changing a variable inside the loop.

beginner

Write a simple while loop that prints numbers from 1 to 5.

#include <iostream> int main() { int i = 1; while (i <= 5) { std::cout << i << std::endl; i++; } return 0; }

beginner

Why is it important to update the variable in the while loop condition?

If you don't update the variable, the condition might never become false, causing the loop to run forever (infinite loop).

What does a while loop do in C++?

A Runs code only if condition is false

B Repeats code while a condition is true

C Runs code once regardless of condition

D Stops the program immediately

A while loop repeats the code block as long as the condition remains true.

What happens if the while loop condition is false at the start?

A The loop runs once

B The program crashes

C The loop runs infinitely

D The loop does not run at all

If the condition is false initially, the while loop code block is skipped.

Which of these can cause an infinite while loop?

A Updating the loop variable correctly

B Using a for loop instead

C Condition always true and no variable update

D Condition false at start

If the condition never becomes false and the variable is not updated, the loop runs forever.

How do you usually stop a while loop?

A By making the condition false inside the loop

B By restarting the program

C By using a break outside the loop

D By ignoring the condition

Changing variables inside the loop to make the condition false stops the loop.

What is the output of this code? int i = 3; while (i > 0) { std::cout << i << " "; i--; }

A 3 2 1

B 1 2 3

C 0 1 2

D No output

The loop prints 3, then 2, then 1, decreasing i each time until i is 0.

Explain how a while loop works and why updating the loop variable is important.

Think about what happens if the condition never changes.

Write a simple example of a while loop that counts down from 5 to 1 and prints each number.

Start with int i = 5; then use while (i > 0).