An enum in C is a user-defined data type that consists of integral constants or constant integers that are given names by the user. The use of enum in C to name the integer values makes the entire program easy to learn, understand, and maintain by the same or even different programmer. The syntax to define an enum in C is by using the ‘enum’ keyword, followed by the name of the enum, and the constants separated by commas within braces. The basic syntax of defining an enum is:

enum enum_name{int_const1, int_const2, int_const3, …. int_constN};

Enums are used for constants when we want a variable to have only a specific set of values. For instance, for weekdays enum, there can be only seven values as there are only seven days in a week. However, a variable can store only one value at a time. We can use enums in C for multiple purposes, such as:

• To store constant values (e.g., weekdays, months, directions, colors in a rainbow)
• For using flags in bit operations
• In switch statements to check for corresponding values

In summary, an enum in C is a user-defined data type that consists of integral constants or constant integers that are given names by the user. It is used to assign names to integral constants, making the program easy to understand and maintain. We use enums for constants when we want a variable to have only a specific set of values.