C Enums

A C enum (enumeration) is a type made of named integer constants. Enums replace unclear numbers like 0, 1 and 2 with meaningful names like LOW, MEDIUM and HIGH.

Creating an Enum

By default the first name is 0 and each next name is one more.

#include <stdio.h>

enum Level { LOW, MEDIUM, HIGH };

int main(void) {
    enum Level current = MEDIUM;
    printf("MEDIUM = %d\n", current);
    printf("HIGH = %d\n", HIGH);
    return 0;
}

MEDIUM = 1
HIGH = 2

Custom Enum Values

You can assign specific values. Names after an assigned one keep counting up from it.

#include <stdio.h>

typedef enum {
    HTTP_OK = 200,
    HTTP_CREATED,          // 201
    HTTP_NOT_FOUND = 404
} HttpStatus;

int main(void) {
    printf("%d %d %d\n", HTTP_OK, HTTP_CREATED, HTTP_NOT_FOUND);
    return 0;
}

200 201 404

Enums with switch

Enums and switch work great together; compilers can even warn you when you forget a case.

#include <stdio.h>

typedef enum { RED, YELLOW, GREEN } Light;

const char *action(Light l) {
    switch (l) {
        case RED:    return "Stop";
        case YELLOW: return "Slow down";
        case GREEN:  return "Go";
    }
    return "Unknown";
}

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

Go

Why Use Enums

• Code reads like plain English.
• Related constants are grouped together.
• Debuggers show enum names instead of raw numbers.
• Compiler warnings help catch missing switch cases.

Frequently asked questions

What is the default value of an enum in C?

The first enumerator is 0 and each following one increases by 1 unless you assign values explicitly.

Should I use enum or #define in C?

Prefer enum for groups of related integer constants. Enums are visible in debuggers, scoped to a type name, and work well with switch warnings.

Can two enum constants have the same value?

Yes, C allows it, for example enum { START = 1, FIRST = 1 }. However, each name must be unique within its scope.