Nested Statements / Loops

1. NESTED IF STATEMENT

A nested if statement is an if condition inside another if block. This allows checking multiple conditions in a hierarchical manner.

Syntax:

if (condition1) {
    if (condition2) {
        // Code to execute if both conditions are true
    }
}

Example 1: Nested If Statement

#include <stdio.h>

int main() {
    int num = 10;

    if (num > 0) {  // Outer if
        printf("The number is positive.\n");

        if (num % 2 == 0) {  // Inner if
            printf("The number is even.\n");
        }
    }

    return 0;
}

Output:

The number is positive.
The number is even.

2. NESTED WHILE LOOP

A nested while loop is a while loop inside another while loop. The inner loop executes completely for each iteration of the outer loop.

Syntax:

while (condition1) {
    while (condition2) {
        // Code to execute
    }
}

Example 2: Multiplication Table using Nested While Loop

#include <stdio.h>

int main() {
    int i = 1, j;

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

    return 0;
}

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

3. NESTED DO-WHILE LOOP

A nested do-while loop is a do-while loop inside another do-while loop. The inner loop will always execute at least once before checking the condition.

Syntax:

do {
    do {
        // Code to execute
    } while (condition2);
} while (condition1);

Example 3: Number Grid using Nested Do-While

#include <stdio.h>

int main() {
    int i = 1, j;

    do {
        j = 1;
        do {
            printf("%d ", j);
            j++;
        } while (j <= 5);

        printf("\n");
        i++;
    } while (i <= 5);

    return 0;
}

Output:

4. NESTED FOR LOOP

A nested for loop is a for loop inside another for loop. The inner loop runs completely for each iteration of the outer loop.

Syntax:

for (initialization; condition1; increment) {
    for (initialization; condition2; increment) {
        // Code to execute
    }
}

Example 4: Printing a Square Pattern

#include <stdio.h>

int main() {
    for (int i = 1; i <= 5; i++) {
        for (int j = 1; j <= 5; j++) {
            printf("* ");
        }
        printf("\n");
    }

    return 0;
}

Output:

* * * * *
* * * * *
* * * * *
* * * * *
* * * * *

5. NESTED SWITCH-CASE

A nested switch-case is when a switch statement is placed inside another switch statement.

Syntax:

switch (variable1) {
    case value1:
        switch (variable2) {
            case value2:
                // Code to execute
                break;
        }
        break;
}

Example 5: Nested Switch-Case for User Role and Permission

#include <stdio.h>

int main() {
    int role = 1; // 1 = Admin, 2 = User
    int action = 2; // 1 = View, 2 = Edit

    switch (role) {
        case 1:
            printf("Role: Admin\n");
            switch (action) {
                case 1:
                    printf("Action: Viewing data\n");
                    break;
                case 2:
                    printf("Action: Editing data\n");
                    break;
                default:
                    printf("Invalid action!\n");
            }
            break;

        case 2:
            printf("Role: User\n");
            switch (action) {
                case 1:
                    printf("Action: Viewing data\n");
                    break;
                default:
                    printf("Users cannot edit data!\n");
            }
            break;

        default:
            printf("Invalid role!\n");
    }

    return 0;
}

Example Output:

Role: Admin
Action: Editing data