Switch-Case in C

The switch statement in C picks one block of code to run based on the value of a single integer or character expression. It is a cleaner alternative to a long if-else ladder when you are comparing one variable against many fixed values.

Basic syntax

switch (expression) {
    case value1:
        /* runs if expression == value1 */
        break;
    case value2:
        /* runs if expression == value2 */
        break;
    default:
        /* runs if no case matched */
        break;
}

The expression must evaluate to an integer type — that includes int and char (a char is just a small integer). Each case label must be a constant, not a variable or a range.

A working example

#include <stdio.h>

int main(void) {
    int day = 3;

    switch (day) {
        case 1:
            printf("Monday\n");
            break;        /* break stops the switch here */
        case 2:
            printf("Tuesday\n");
            break;
        case 3:
            printf("Wednesday\n");   /* this matches, prints, then breaks */
            break;
        default:
            printf("Some other day\n");
            break;
    }
    return 0;
}

The matching case runs; break then jumps out of the switch.

Why break matters: fall-through

If you forget break, C keeps running into the next case — this is called fall-through. Sometimes it is a bug, sometimes it is exactly what you want when several cases share the same action:

#include <stdio.h>

int main(void) {
    char grade = 'B';

    switch (grade) {
        case 'A':
        case 'B':                 /* both A and B fall through to here */
            printf("Well done!\n");
            break;
        case 'C':
            printf("You passed.\n");
            break;
        default:
            printf("Keep practising.\n");
            break;
    }
    return 0;
}

Here 'A' and 'B' deliberately share one block. When fall-through is intentional, add a comment so readers know it's not a missing break.

The default case

default is the catch-all, like the final else. It can appear anywhere in the switch, but by convention it goes last. It is optional, but including it makes your code handle unexpected values gracefully.

A practical menu

switch is a natural fit for menu-driven programs, where the user picks an option and you run the matching action:

#include <stdio.h>

int main(void) {
    int choice;

    printf("1) Add  2) Subtract  3) Quit\n");
    printf("Choose: ");
    if (scanf("%d", &choice) != 1) {   /* guard against bad input */
        return 1;
    }

    switch (choice) {
        case 1:
            printf("You chose Add.\n");
            break;
        case 2:
            printf("You chose Subtract.\n");
            break;
        case 3:
            printf("Goodbye!\n");
            break;
        default:
            printf("Unknown option.\n");   /* catches everything else */
            break;
    }
    return 0;
}

Pairing this with a do-while loop lets the menu repeat until the user chooses Quit.

switch vs if-else

• Use switch when one variable is tested against several constant values (menu choices, status codes, single characters).
• Use if-else for ranges (score >= 75), floating-point tests, or compound conditions with && / ||.
• A switch can be faster and clearer than a long chain of else if, because the reader sees at a glance that one variable drives every branch.

Common mistakes

• Forgetting break, causing unintended fall-through into later cases.
• Using a variable or range as a case label: case x: or case 1...5: are not valid standard C. Case labels must be compile-time constants.
• Using a float or double in switch (...): only integer types (including char) are allowed.
• Duplicate case values: two case 2: labels is a compile error.
• Declaring a variable inside a case without braces: declarations that need initialization can clash across cases. Wrap a case body in { } if you declare variables there.

FAQ

Can I use strings in a switch? No. C switch only works on integer types. For strings, compare with strcmp inside if-else.

Does the order of cases matter? Not for correctness (each is matched by value), but keep them readable and put default last.

Keep going at the hub C Programming, and compare with If-Else in C and Functions in C.

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