Chapter 26 of 37

Enumerations

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Sometimes a variable can only have a small set of possible values.

For example, a day can be Monday, Tuesday, Wednesday, and so on. Instead of using numbers everywhere, C provides enumerations, or enum.

What is an Enumeration?

An enumeration is a user-defined type that consists of a set of named integer constants.

It is created using the enum keyword.

enum Day
{
    MONDAY,
    TUESDAY,
    WEDNESDAY
};

Here, MONDAY, TUESDAY, and WEDNESDAY are enumeration constants.

By default, the first value is 0, the next is 1, and so on.

MONDAY     → 0
TUESDAY    → 1
WEDNESDAY  → 2

Creating an Enum Variable

We can create a variable using the enumeration:

enum Day today;

today = TUESDAY;

We can then use it in the program:

printf("%d", today);

Output:

1

The names make the code easier to understand than using numbers directly.

Assigning Custom Values

We can also assign our own integer values:

enum Status
{
    FAILED = 0,
    PASSED = 1,
    PENDING = 5
};

Now:

FAILED  → 0
PASSED  → 1
PENDING → 5

If you omit a value, numbering continues from the previous value.

Example

#include <stdio.h>

enum Day
{
    MONDAY,
    TUESDAY,
    WEDNESDAY
};

int main()
{
    enum Day today = TUESDAY;

    if (today == TUESDAY)
    {
        printf("Today is Tuesday");
    }

    return 0;
}

Output:

Today is Tuesday

Why Use Enumerations?

Enums are useful when a variable has a fixed set of named choices.

For example:

  • Days of the week

  • Months

  • Traffic-light states

  • User roles

  • Program states

  • Error or status codes

They make programs more readable and easier to maintain.

Enum vs Constant

You can also create constants using #define:

#define RED 0
#define GREEN 1
#define BLUE 2

But an enum groups related named integer constants together:

enum Color
{
    RED,
    GREEN,
    BLUE
};

This makes the relationship between the values clearer.

In Simple Words

An enumeration (enum) lets us give meaningful names to a set of integer constants.

For example:

enum Color
{
    RED,
    GREEN,
    BLUE
};

Instead of writing numbers like 0, 1, and 2, we can use meaningful names like RED, GREEN, and BLUE.

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