C do-while Loop

C do-while Loop (Beginner → Advanced)

In C do-while Loop is a loop that executes its body at least once, even if the condition is false.

 This is the main difference from while and for loops.

 What is do-while Loop?

A loop that checks the condition after executing the loop body.

 Syntax of do-while Loop

• Semicolon (;) is mandatory

Simple do-while Example

Print 1 to 5

Output: 1 2 3 4 5

Proof: Executes At Least Once

Output:

•  Condition is false, but body executes once

do-while with User Input

•  Perfect for input validation

 Menu-Driven Program Using do-while (Interview Favorite)

•  Common in real applications

do-while with break

Output: 1 2 3

do-while with continue

Output: 1 2 4 5

do-while vs while

 Common Mistakes

•  Forgetting semicolon after while(condition);
• Infinite loop due to wrong condition
•  Misusing continue
•  Not updating loop variable

Interview Questions (Must Prepare)

1. Difference between while and do-while

2. Does do-while execute if condition is false?

3. Why semicolon is mandatory?

4. Real-life use of do-while

5. Can do-while replace while?

Real-Life Use Cases

• Menu-driven programs

• Input validation

• Embedded systems (sensor checks)

• Games & UI loops

 Summary

• do-while runs at least once
•  Condition is checked at the end
•  Best for menus & validations
•  Semicolon is mandatory
•  Very important for interviews & real programs