Enum (Enumerated Types) Basics

This lesson covers the basics of C's Enum (enumerated type), so you can work with a fixed set of options under readable names. It's for anyone searching "C enum usage."

enum lets you create an "enumerated type" representing only a fixed set of options. Use it when you want to limit a value to a known set of categories ahead of time — like "a traffic light is only red, green, or yellow."

The example defines three options with typedef enum { RED, GREEN, BLUE } Color;, and assigns one option, Color c = RED;, to a variable. Notice that internally, C's enum is treated as a sequence of integers starting at 0.

A common early mistake is displaying an enum's value with printf() and seeing the number rather than the name. Unlike some other languages, it's not automatically displayed by name — you'd need to write your own conversion logic to display the name.

In real projects, using a named enum instead of scattering plain strings or numbers everywhere makes your code's intent much clearer.

📖 Reference code

#include <stdio.h>

typedef enum {
    RED,
    GREEN,
    BLUE
} Color;

int main(void) {
    Color c = RED;
    printf("%d\n", c);
    printf("%d %d\n", GREEN, BLUE);
    return 0;
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run C directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).