switch Statements

switch picks one of several branches based on the value of an integer expression. It's tidier than a long else if chain when you're comparing one value against many constants — menu choices, commands, states.

Basic switch

#include <stdio.h>

int main(void) {
    int day = 3;
    switch (day) {
        case 1:
            printf("Monday\n");
            break;
        case 2:
            printf("Tuesday\n");
            break;
        case 3:
            printf("Wednesday\n");
            break;
        default:
            printf("Some other day\n");
            break;
    }
    return 0;
}

Output

Wednesday

The expression is evaluated once and execution jumps to the matching case. break leaves the switch; default runs when nothing matches.

What can be switched on

The expression must be an integer type — int, char, an enum…
Each case label must be a constant known at compile time: a literal, an enum constant or a #define. Not a variable, a range, a double or a string.
No two labels can have the same value.

Fall-through

Without break, execution simply continues into the next case. That's useful when several values share code:

#include <stdio.h>

int main(void) {
    const char *word = "Programming";
    int vowels = 0, others = 0;
    for (int i = 0; word[i] != '\0'; i++) {
        switch (word[i]) {
            case 'a': case 'e': case 'i': case 'o': case 'u':
            case 'A': case 'E': case 'I': case 'O': case 'U':
                vowels++;
                break;
            default:
                others++;
                break;
        }
    }
    printf("%d vowels, %d other letters\n", vowels, others);
    return 0;
}

Output

3 vowels, 8 other letters

Forgetting a break by accident is a common bug. Compilers can warn about it with -Wimplicit-fallthrough; when you fall through on purpose after some code, say so with a comment such as // fall through (or C23's [[fallthrough]];).

#include <stdio.h>

int main(void) {
    int level = 2;
    printf("Unlocked:");
    switch (level) {
        case 3:
            printf(" castle");
            // fall through
        case 2:
            printf(" forest");
            // fall through
        case 1:
            printf(" village");
            break;
    }
    printf("\n");
    return 0;
}

Output

Unlocked: forest village

A command menu

#include <stdio.h>

int main(void) {
    const char commands[] = "+-*/x";
    double a = 12, b = 4;
    for (int i = 0; commands[i] != '\0'; i++) {
        char op = commands[i];
        switch (op) {
            case '+': printf("%g + %g = %g\n", a, b, a + b); break;
            case '-': printf("%g - %g = %g\n", a, b, a - b); break;
            case '*': printf("%g * %g = %g\n", a, b, a * b); break;
            case '/':
                if (b == 0) {
                    printf("cannot divide by zero\n");
                } else {
                    printf("%g / %g = %g\n", a, b, a / b);
                }
                break;
            default:
                printf("unknown operator '%c'\n", op);
                break;
        }
    }
    return 0;
}

Output

12 + 4 = 16
12 - 4 = 8
12 * 4 = 48
12 / 4 = 3
unknown operator 'x'

Short cases can sit on one line. A case with several statements, or with its own variables, is clearer with braces: case '/': { … break; }.

switch with enums

Switching on an enum has a bonus: with -Wall, the compiler warns if you forgot to handle one of its values (as long as there's no default):

#include <stdio.h>

enum light { RED, AMBER, GREEN };

const char *action(enum light l) {
    switch (l) {
        case RED:   return "stop";
        case GREEN: return "go";
    }
    return "?";
}

int main(void) {
    printf("%s\n", action(AMBER));
    return 0;
}

Compiler warnings

main.c:6:13: warning: enumeration value 'AMBER' not handled in switch [-Wswitch]

switch or if?

Use switch for one integer value compared against many constants. Use if/else if for ranges (score >= 90), conditions on different variables, floating-point values or strings.

Try it yourself

Print the number of days in each month of 2026 using a switch with grouped cases.

#include <stdio.h>

int main(void) {
    for (int month = 1; month <= 12; month++) {
        int days;
        switch (month) {
            case 2:
                days = 28;
                break;
            case 4: case 6: case 9: case 11:
                days = 30;
                break;
            default:
                days = 31;
                break;
        }
        printf("%d:%d ", month, days);
    }
    printf("\n");
    return 0;
}

Edit the code, copy it into main.c, then compile and run it with cc -std=c17 -Wall main.c -o main && ./main. How to set up a C compiler

Output

1:31 2:28 3:31 4:30 5:31 6:30 7:31 8:31 9:30 10:31 11:30 12:31

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