Enums

When you have a variable that should only hold one value from a small set — like days of the week or error codes — you could use integers. But enum gives names to those values, making your code self-documenting and less error-prone.

Defining and Using Enums

An enum creates a new type with named constants. By default, the first constant is 0, the next is 1, and so on — but you can set your own values.

#include 
enum Day { MON, TUE, WED, THU, FRI, SAT, SUN };
int main() {
  enum Day today = WED;
  printf("Today is day number %d\n", today);
  if (today == SAT || today == SUN) {
    printf("Weekend!\n");
  } else {
    printf("Weekday\n");
  }
  return 0;
}
    

Custom Enum Values

You can assign specific integers to enum constants. This is great for representing status codes or bit flags where the numeric value matters.

#include 
enum HttpStatus {
  OK = 200,
  NOT_FOUND = 404,
  SERVER_ERROR = 500
};
int main() {
  enum HttpStatus status = NOT_FOUND;
  printf("Status code: %d\n", status);
  if (status == NOT_FOUND) {
    printf("Page not found!\n");
  }
  return 0;
}
    

When to Use Enums

Use enums whenever a variable should only take one of a fixed set of related values. They make your code safer (you can't accidentally type a wrong number) and more readable (the name tells you what it means).

#include 
enum Color { RED, GREEN, BLUE };
void printColor(enum Color c) {
  switch (c) {
    case RED:   printf("Red\n"); break;
    case GREEN: printf("Green\n"); break;
    case BLUE:  printf("Blue\n"); break;
  }
}
int main() {
  enum Color c = GREEN;
  printColor(c);
  return 0;
}