What is a Loop?

A loop in C is a control structure that allows us to repeat a block of code multiple times without writing it again and again.

Purposes of Loop

  • To reduce repetition in code.
  • To make programs shorter, cleaner, and easier to maintain.
  • To perform tasks multiple times like printing, adding numbers, processing arrays, etc.
  • To save time and effort for both programmer and computer.

For Loop in C

Syntax:

for(initialization; condition; increment/decrement) {
    // statements to repeat
}

Flowchart of For Loop

for loop flowchart

Working of For Loop

  • The loop initializes a variable (like i=1).
  • It checks the condition (e.g., i <= 10).
  • If true → executes the block.
  • After block → updates the variable (e.g., i++).
  • Goes back to condition check.
  • Repeats until condition becomes false.

Examples

Example 1 – Print “I love Pakistan” 10 times

#include <stdio.h>

int main() {
    int i;
    for(i = 1; i <= 10; i++) {
        printf("I love Pakistan\n");
    }
    return 0;
}

Output:

I love Pakistan
I love Pakistan
I love Pakistan
...
(total 10 times)

Example 2 – Print “I am a Programmer” 20 times

#include <stdio.h>

int main() {
    int i;
    for(i = 1; i <= 20; i++) {
        printf("I am a Programmer\n");
    }
    return 0;
}

Output:

I am a Programmer
I am a Programmer
...
(total 20 times)

MCQs on Loops in C

  1. What is the main purpose of using a loop in C?
    A) To make the program slower
    B) To avoid repeating code again and again
    C) To create errors in the program
    D) To replace functions

    Answer: B) To avoid repeating code again and again

  2. Which of the following is the correct syntax of a for loop in C?
    A) for(condition; initialization; update)
    B) for(initialization; condition; update)
    C) for(update; condition; initialization)
    D) for(initialization; update; condition)

    Answer: B) for(initialization; condition; update

  3. In a for loop, which part is executed first?
    A) Condition
    B) Initialization
    C) Update
    D) Body of the loop

    Answer: B) Initialization

  4. What will the following code print?
    for(int i = 1; i <= 5; i++) {
    printf("Hello\n");
}
    A) Prints "Hello" 1 time
    B) Prints "Hello" 5 times
    C) Prints "Hello" infinitely
    D) Error in code

    Answer: B) Prints "Hello" 5 times

  5. What is the output of this code?
    for(int i = 1; i <= 3; i++) {
    printf("%d ", i);
}
    A) 1 2 3
    B) 0 1 2
    C) 1 2 3 4
    D) Infinite Loop

    Answer: A) 1 2 3

  6. In a for loop, the update step is executed:
    A) Before initialization
    B) After the loop body executes
    C) Before checking condition
    D) Never

    Answer: B) After the loop body executes

  7. Which loop guarantees at least one execution of the body, even if the condition is false?
    A) for loop
    B) while loop
    C) do-while loop
    D) nested loop

    Answer: C) do-while loop

  8. If the condition in a for loop is always true, what will happen?
    A) Program will stop immediately
    B) Program will run infinitely
    C) Program will run once
    D) Error will occur

    Answer: B) Program will run infinitely