Explain nested switch case in C language

Nested switch case in C allows you to place one switch statement inside another switch statement. This technique is useful when you need to perform multi-level decision-making based on different variables or conditions.

Syntax

switch (outer_expression) {
    case value1:
        switch (inner_expression) {
            case inner_value1:
                // statements
                break;
            case inner_value2:
                // statements
                break;
            default:
                // default statements
        }
        break;
    case value2:
        // statements
        break;
    default:
        // default statements
}

Key Rules

• The inner switch statement is completely independent of the outer switch
• Case values of inner and outer switch can have common values without conflict
• Each case must end with a colon (:) and include a break statement
• Both outer and inner switches can have their own default cases
• Proper indentation improves readability of nested structures

Example: Password Validation System

This example demonstrates a simple authentication system using nested switch statements −

#include <stdio.h>

int main() {
    int userid;
    int password;
    
    printf("Enter User ID: ");
    scanf("%d", &userid);
    
    switch (userid) {
        case 1234:
            printf("Enter Password: ");
            scanf("%d", &password);
            switch (password) {
                case 5678:
                    printf("Login Successful! Welcome to TutorialsPoint<br>");
                    break;
                case 0000:
                    printf("Using default password. Please change it.<br>");
                    break;
                default:
                    printf("Incorrect password!<br>");
                    break;
            }
            break;
            
        case 9999:
            printf("Enter Admin Password: ");
            scanf("%d", &password);
            switch (password) {
                case 1111:
                    printf("Admin access granted!<br>");
                    break;
                default:
                    printf("Invalid admin password!<br>");
                    break;
            }
            break;
            
        default:
            printf("Invalid User ID!<br>");
            break;
    }
    
    return 0;
}

Enter User ID: 1234
Enter Password: 5678
Login Successful! Welcome to TutorialsPoint

Example: Menu-Driven Calculator

Here's another example showing nested switch for a calculator with operation subcategories −

#include <stdio.h>

int main() {
    int choice, subChoice;
    float a = 10.0, b = 5.0, result;
    
    printf("Calculator Menu:<br>");
    printf("1. Basic Operations<br>2. Advanced Operations<br>");
    printf("Enter your choice: ");
    scanf("%d", &choice);
    
    switch (choice) {
        case 1:
            printf("Basic Operations:<br>");
            printf("1. Addition<br>2. Subtraction<br>");
            printf("Enter operation: ");
            scanf("%d", &subChoice);
            
            switch (subChoice) {
                case 1:
                    result = a + b;
                    printf("%.2f + %.2f = %.2f<br>", a, b, result);
                    break;
                case 2:
                    result = a - b;
                    printf("%.2f - %.2f = %.2f<br>", a, b, result);
                    break;
                default:
                    printf("Invalid basic operation!<br>");
                    break;
            }
            break;
            
        case 2:
            printf("Advanced Operations:<br>");
            printf("1. Multiplication<br>2. Division<br>");
            printf("Enter operation: ");
            scanf("%d", &subChoice);
            
            switch (subChoice) {
                case 1:
                    result = a * b;
                    printf("%.2f * %.2f = %.2f<br>", a, b, result);
                    break;
                case 2:
                    result = a / b;
                    printf("%.2f / %.2f = %.2f<br>", a, b, result);
                    break;
                default:
                    printf("Invalid advanced operation!<br>");
                    break;
            }
            break;
            
        default:
            printf("Invalid menu choice!<br>");
            break;
    }
    
    return 0;
}

Calculator Menu:
1. Basic Operations
2. Advanced Operations
Enter your choice: 1
Basic Operations:
1. Addition
2. Subtraction
Enter operation: 1
10.00 + 5.00 = 15.00

Conclusion

Nested switch statements provide a structured way to handle complex multi-level decision-making in C. They improve code organization and readability when dealing with hierarchical menu systems or multi-step validation processes.