Enum Basics

Declaring and using

enum Color { RED, GREEN, BLUE };

enum Color c = GREEN;

The compiler assigns values starting at 0: RED=0, GREEN=1, BLUE=2. You can pin or offset values:

enum Level { LOW = 1, MEDIUM, HIGH };   // 1, 2, 3
enum Mask  { BIT0 = 1, BIT2 = 4 };      // explicit

Why not just ints?

Magic numbers (if (s == 2)) hide meaning; enum names carry it (if (s == STATE_PAUSED)). The compiler also type-checks the intent, and switch coverage warnings catch missing cases.

Enums and switch

enum Color invert(enum Color c) {
    switch (c) {
        case RED:   return BLUE;
        case BLUE:  return RED;
        case GREEN: return GREEN;
    }
    return c;   // defensive: reachable only on invalid input
}

Each case names a constant — no more guessing what 1 meant.