While loop in C - Cheat Sheet & Quick Revision

Recall & Review

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What is a while loop in C?

A while loop repeatedly executes a block of code as long as a given condition is true.

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How does the while loop check its condition?

Before each iteration, the while loop checks the condition. If it is true, the loop runs the code inside; if false, it stops.

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

The loop body does not run even once if the condition is false initially.

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Write a simple while loop that prints numbers 1 to 3.

int i = 1; while (i <= 3) { printf("%d\n", i); i++; }

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Why is it important to update the loop variable inside a while loop?

Updating the loop variable prevents an infinite loop by eventually making the condition false.

What does a while loop do in C?

A Repeats code while a condition is true

B Runs code once regardless of condition

C Runs code only if condition is false

D Runs code a fixed number of times

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

When is the condition in a while loop checked?

A Never

B After each iteration

C Only once at the start

D Before each iteration

The condition is checked before running the loop body each time.

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

A Loop runs once

B Loop body does not run

C Loop runs infinitely

D Loop runs twice

If the condition is false initially, the loop body is skipped.

Which of these can cause an infinite while loop?

A Not updating the loop variable

B Updating the loop variable correctly

C Using <code>for</code> loop instead

D Printing inside the loop

If the loop variable is not updated, the condition may never become false, causing an infinite loop.

What is the output of this code? int i = 1; while (i <= 2) { printf("%d ", i); i++; }

A 2 3

B 1 2 3

C 1 2

D No output

The loop prints 1 and 2, then stops when i becomes 3.

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

Think about what happens if the condition never changes.

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

Start with int i = 5 and decrease i each time.