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Nested Loops in C

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Introduction

In C programming, sometimes we need to repeat a loop inside another loop.
This is called a nested loop.

👉 Nested loops are very useful for solving problems like patterns, matrices, and complex iterations.

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What is a Nested Loop?

A nested loop is:
👉 A loop inside another loop

• Outer loop → controls overall iterations
• Inner loop → runs completely for each outer loop cycle

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Basic Syntax

for (initialization; condition; increment) {
    
    for (initialization; condition; increment) {
        // inner loop code
    }

}

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How Nested Loop Works

👉 Example flow:

• Outer loop runs 1 time
• Inner loop runs fully
• Then outer loop repeats

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Example 1: Simple Nested Loop

#include <stdio.h>

int main() {
    int i, j;

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

    return 0;
}

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Output

i = 1, j = 1
i = 1, j = 2
i = 1, j = 3
i = 2, j = 1
i = 2, j = 2
i = 2, j = 3
i = 3, j = 1
i = 3, j = 2
i = 3, j = 3

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Example 2: Star Pattern

#include <stdio.h>

int main() {
    int i, j;

    for (i = 1; i <= 4; i++) {
        for (j = 1; j <= i; j++) {
            printf("* ");
        }
        printf("\n");
    }

    return 0;
}

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Output

* 
* * 
* * * 
* * * * 

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Example 3: Multiplication Table

#include <stdio.h>

int main() {
    int i, j;

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

    return 0;
}

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Output

1 2 3 4 5
2 4 6 8 10
3 6 9 12 15
4 8 12 16 20
5 10 15 20 25

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Types of Nested Loops

• Nested for loops
• Nested while loops
• Mixed loops (for inside while, etc.)

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Real-World Uses

• Pattern printing
• Matrix operations
• Game development logic
• Data processing

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Common Mistakes

• ❌ Wrong loop condition
• ❌ Incorrect nesting
• ❌ Infinite loops
• ❌ Forgetting printf("\n")

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Pro Tips

• ✔ Always understand loop flow
• ✔ Practice pattern programs
• ✔ Use meaningful variables
• ✔ Avoid too many nested levels

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Conclusion

Nested loops are powerful tools in C programming. They allow you to handle complex problems like patterns and matrices efficiently.

Mastering nested loops will greatly improve your coding skills.

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