C Nested Loops

Nested loops in C refer to loops placed inside another loop. They are commonly used for working with multi-dimensional arrays, printing patterns, and solving complex iterative problems.

In this tutorial, you will learn the syntax of nested loops in C programming, and how to use them effectively with examples.

Syntax of Nested Loops

In a nested loop structure, the inner loop runs completely for each iteration of the outer loop.

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for (initialization; condition; increment/decrement) {
    for (initialization; condition; increment/decrement) {
        // Code to execute in each iteration of inner loop
    }
    // Code to execute in each iteration of outer loop
}

Explanation of Syntax:

  1. The outer for loop executes first.
  2. For each iteration of the outer loop, the inner for loop executes completely.
  3. After the inner loop completes, control moves back to the outer loop for the next iteration.

Examples of Nested Loops

1 Printing a Number Pattern

In this example, we will use nested loops to print a number pattern.

main.c

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#include <stdio.h>

int main() {
    for (int i = 1; i <= 5; i++) {
        for (int j = 1; j <= 3; j++) {
            printf("%d ", j);
        }
        printf("\n");
    }
    return 0;
}

Explanation:

  1. The outer loop runs from 1 to 5, controlling the rows.
  2. The inner loop runs from 1 to 3, printing numbers in a row.
  3. After each iteration of the inner loop, a new line is printed.

Output:

1 2 3 
1 2 3 
1 2 3
1 2 3 
1 2 3

2 Creating a Multiplication Table

We will use nested loops to print a multiplication table from 1 to 5.

main.c

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#include <stdio.h>

int main() {
    for (int i = 1; i <= 5; i++) {
        for (int j = 1; j <= 5; j++) {
            printf("%d\t", i * j);
        }
        printf("\n");
    }
    return 0;
}

Explanation:

  1. The outer loop iterates through numbers 1 to 5.
  2. The inner loop multiplies the outer loop index with the inner loop index.
  3. The result is printed with a tab space.
  4. After each row, a new line is printed.

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

Conclusion

In this tutorial, we explored nested loops in C, including:

  1. The syntax of nested loops and how they work.
  2. A number pattern program using nested loops.
  3. A multiplication table program using nested loops.