Switch Case

Imagine a TV remote with different buttons, and each button performs a specific action (like changing channels, adjusting volume, or powering off the TV). Using a switch-case statement, you can simulate the behavior of a TV remote where pressing a certain button triggers a specific response. For better understanding see the short video below

The switch statement in C is a control structure used to execute one of many code blocks based on the value of an expression. It’s particularly useful when there are multiple conditions to check, as it provides a cleaner and more efficient alternative to multiple if-else statements.

How It Works

• The switch statement evaluates an expression, usually a variable.
• Based on the result, it jumps to the corresponding case label.
• If a match is found, it executes the code under that case.
• The break statement is used to exit the switch structure once the matched case block is complete.
• If none of the cases match, the default block (optional) executes as a fallback.

Syntax

switch (expression) {
    case constant1:
        // code block 1
        break;
    case constant2:
        // code block 2
        break;
    // add more cases as needed
    default:
        // code block for default case
        break;
}

• expression: This is the value that the switch statement evaluates. It can be of integral type (char, int, long) or an enumeration.
• case constant1, case constant2, …: These are the possible values that the expression can take. If the expression matches one of these constants, the corresponding code block following that case label will be executed.
• break: The break statement is used to terminate the switch statement and exit the switch block. If break is omitted, control will fall through to the next case.
• default: This is an optional case label that is used when none of the other cases match the value of the expression. It’s similar to the else clause in an if-else statement.

Flowchart:

Here’s an example of using the switch statement:

Example 1: Enter Keyword for a choice

#include <stdio.h>

int main() {
    int choice = 2;
    
    switch (choice) {
        case 1:
            printf("You chose option 1\n");
            break;
        case 2:
            printf("You chose option 2\n");
            break;
        case 3:
            printf("You chose option 3\n");
            break;
        default:
            printf("Invalid choice\n");
            break;
    }

    return 0;
}

Output:

You chose option 2

Explanation:

• The switch keyword evaluates the value of choice. Based on its value, it will match one of the case labels.
• Case 1: If choice == 1, the program will execute the code inside this block (printf("You chose option 1\n");) and then exit the switch using the break statement.
• Case 2: If choice == 2 (which it is in this case), the program will execute the code in this block, printing “You chose option 2” to the console, and then exit the switch with break.
• Case 3: If choice == 3, it will print “You chose option 3”.
• Default Case: If none of the case values match, the program will execute the default block and print “Invalid choice”.
• The break statement prevents the program from continuing to check the next cases after the matching case is executed. Without the break, the program would execute all the code blocks after the matched case, even if they don’t match (this is called “fall-through”).

Example 2: Number to Day Conversion

#include <stdio.h>

int main() {
    int day;
    printf("Enter a number (1-7) to get the corresponding day of the week: ");
    scanf("%d", &day);

    switch(day) {
        case 1:
            printf("Sunday\n");
            break;
        case 2:
            printf("Monday\n");
            break;
        case 3:
            printf("Tuesday\n");
            break;
        case 4:
            printf("Wednesday\n");
            break;
        case 5:
            printf("Thursday\n");
            break;
        case 6:
            printf("Friday\n");
            break;
        case 7:
            printf("Saturday\n");
            break;
        default:
            printf("Invalid day number. Please enter a number between 1 and 7.\n");
    }

    return 0;
}

Explanation

1. Expression: day is the expression evaluated in the switch statement.
2. Cases: Each case label represents a possible value for day. When a match is found, the corresponding code executes.
3. Break Statements: The break statement prevents the execution from falling through to subsequent cases, ensuring only the matched case executes.
4. Default Case: The default block is executed if none of the cases match. Here, it catches invalid inputs.

Use Cases and Advantages of switch

• Menu-driven Programs: When building programs with menu options, switch can efficiently handle the selection logic.
• Improved Readability: Using switch instead of if-else for multi-option selections makes the code more readable and structured.
• Efficiency: The switch statement may be more efficient than multiple if-else checks, depending on the compiler.