Enums

An enum (enumeration) is a user-defined data type in C. It is used to assign names to integral constants. The principal purpose of these names is to create a program that is easy to read and maintain. It is defined using the enum keyword.

Syntax

enum name
{
  memberName1 = <integral constant>,
  memberName2,
  memberName3,
  ...
  memberNameN
};

An enum is made up of members where each memberName can have a defined integral constant (e.g. 0, 10, 2) or just the memberName.

Examples

If we do not explicitly assign values to enum day, the compiler by default assigns values starting from 0. For instance, sunday gets a value of 0, monday gets 1, and so on.

#include <stdio.h>
enum fruits {apple, orange, banana, peach, grape};

int main()
{
    enum fruits d = banana;
    printf("The fruit number stored in d is %d", d);
    return 0;
}

This example results in the following output:

The fruit number stored in d is 2

Two enum names can have the same value. For instance, both Running and In_Progress have the same value of 1.

#include <stdio.h>
enum State {Todo = 0, Running = 1, In_Progress = 1};
int main()
{
    printf("%d, %d, %d", Todo, Running, In_Progress);
    return 0;
}

This example results in the following output.

0, 1, 1

We can assign values to a particular name in any order. All unassigned names get value as the value of the previous name plus one.

#include <stdio.h>
enum day {sunday = 1, monday, tuesday = 20,
          wednesday, thursday = 10, friday, saturday};

int main()
{
    printf("%d %d %d %d %d %d %d", sunday, monday, tuesday,
            wednesday, thursday, friday, saturday);
    return 0;
}

This example results in the following output:

1 2 20 21 10 11 12

Note: All enum constants must be unique in their scope.