C While Loop

 C while Loop (Complete Tutorial: Beginner → Advanced)

The while loop in C language is used when the number of iterations is not known beforehand.
It checks the condition first, and only if it’s true does the loop body execute.

 What is a while Loop?

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

 Syntax of while Loop

Execution Flow

1. Check condition

2. If true → execute loop body

3. Update loop variable

4. Go back to step 1

 Simple while Loop Example

Print numbers from 1 to 5

Output

while Loop with User Input

•  Loop depends on user input
•  Very common in real programs

 Sum of Digits Using while (Interview Favorite)

Reverse a Number Using while

while Loop with Arrays

• Used when size is dynamic or unknown

 Infinite while Loop

 Used in:

• Embedded systems

• Servers

• Game loops

 Must use break to exit

while Loop with break

Output

while Loop with continue

Output

•  Always update loop variable before continue to avoid infinite loop

while vs for Loop

Common Mistakes

•  Forgetting to update loop variable
• Infinite loop due to wrong condition
•  Using = instead of ==
• Misusing continue

 Interview Questions (Must Prepare)

1. When should we use a while loop?

2. Difference between while and do-while

3. Can a while loop be infinite?

4. What happens if condition is false initially?

5. Role of break and continue in while

 Summary

• while loop checks condition first
•  Best when number of iterations is unknown
•  Widely used in menus, validation, embedded systems
•  Essential for logic building & interviews