C Enumeration

In C programming language, an enumeration is a user-defined data type that consists of a set of named constants, also known as enumerators. Enumerations are defined using the enum keyword, which defines a new type that can be used to declare variables of that type.

Here's the syntax for defining an enumeration:

enum <enumeration_name> {
    <enumerator_1>,
    <enumerator_2>,
    // ...
};

For example, let's define a Color enumeration that represents different colors:

enum Color {
    RED,
    GREEN,
    BLUE
};

Once an enumeration is defined, you can declare variables of that type:

enum Color c1;

You can also initialize an enumeration variable at the time of declaration:

enum Color c2 = GREEN;

You can access individual enumerators of an enumeration using their names:

c1 = RED;
printf("c1 = %d\n", c1); // Output: c1 = 0
printf("c2 = %d\n", c2); // Output: c2 = 1

In C, the first enumerator in an enumeration has a default value of 0, and subsequent enumerators are assigned values that are one greater than the previous enumerator. However, you can explicitly assign values to individual enumerators:

enum Color {
    RED = 1,
    GREEN = 2,
    BLUE = 4
};

Here's an example program that demonstrates the use of enumerations in C:

#include <stdio.h>

enum Color {
    RED,
    GREEN,
    BLUE
};

int main() {
    enum Color c1;
    enum Color c2 = GREEN;

    c1 = RED;
    printf("c1 = %d\n", c1); // Output: c1 = 0
    printf("c2 = %d\n", c2); // Output: c2 = 1

    return 0;
}

This program declares a Color enumeration, declares two variables c1 and c2, initializes c2 with the value GREEN, updates c1 with the value RED, and prints out the values of both variables.