Dharani Tech Edu Hub

Loops in C

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Introduction

In programming, repeating a task multiple times is very common. Writing the same code again and again is not efficient.
This is where loops come into play.

👉 Loops allow us to execute a block of code multiple times based on a condition.

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What is a Loop?

A loop is a control structure that:

• Executes a block of code repeatedly
• Stops when a condition becomes false

👉 In simple terms:
Loop = Repeat until condition fails

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Why Do We Use Loops?

• ✔ Reduce code repetition
• ✔ Save time and effort
• ✔ Make programs efficient
• ✔ Handle large data easily

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Types of Loops in C

1. for loop
2. while loop
3. do-while loop

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1. for Loop

Used when the number of iterations is known.

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Syntax

for (initialization; condition; increment/decrement) {
    // code
}

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How It Works

1. Initialization executes once
2. Condition is checked
3. Code executes if condition is true
4. Increment/decrement happens
5. Repeat

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Example

#include <stdio.h>

int main() {
    int i;

    for (i = 1; i <= 5; i++) {
        printf("%d\n", i);
    }

    return 0;
}

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Output

1
2
3
4
5

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Use Case

👉 Printing numbers, patterns, fixed iterations

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2. while Loop

Used when the number of iterations is not known.

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Syntax

while (condition) {
    // code
}

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How It Works

• Condition is checked first
• If true → code runs
• If false → loop stops

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Example

#include <stdio.h>

int main() {
    int i = 1;

    while (i <= 5) {
        printf("%d\n", i);
        i++;
    }

    return 0;
}

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Output

1
2
3
4
5

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Use Case

👉 User input loops, unknown iterations

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3. do-while Loop

Executes code at least once.

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Syntax

do {
    // code
} while (condition);

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How It Works

• Code executes first
• Then condition is checked

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Example

#include <stdio.h>

int main() {
    int i = 1;

    do {
        printf("%d\n", i);
        i++;
    } while (i <= 5);

    return 0;
}

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Output

1
2
3
4
5

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Use Case

👉 Menu-driven programs, user interaction

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Nested Loops (Important)

A loop inside another loop is called a nested loop.

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Example

#include <stdio.h>

int main() {
    int i, j;

    for (i = 1; i <= 3; i++) {
        for (j = 1; j <= 3; j++) {
            printf("* ");
        }
        printf("\n");
    }

    return 0;
}

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Output

* * * 
* * * 
* * * 

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⚠️ Infinite Loop

A loop that never ends.

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Example

while(1) {
    printf("Infinite Loop");
}

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Comparison Table

Loop Type	Condition Check	Use Case
for	Before execution	Known iterations
while	Before execution	Unknown iterations
do-while	After execution	Execute at least once

Common Mistakes

• ❌ Forgetting increment/decrement
• ❌ Writing wrong condition
• ❌ Creating infinite loops
• ❌ Using wrong loop type

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Pro Tips

• ✔ Use for for known loops
• ✔ Use while for conditions
• ✔ Use do-while for user interaction
• ✔ Avoid deep nesting
• ✔ Always check loop condition carefully

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Conclusion

Loops are a fundamental concept in C programming. They help reduce code repetition and improve efficiency.

Mastering loops will help you solve complex problems easily.

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👉 This article is part of Dharani Tech Edu Hub — where learning programming is made simple and practical.