Enum in C

The enum in C is also known as the enumerated type. It is a user-defined data type that consists of integer values, and it provides meaningful names to these values. The use of enum in C makes the program easy to understand and maintain. The enum is defined by using the enum keyword.

The following is the way to define the enum in C:

In the above declaration, we define the enum named as flag containing 'N' integer constants. The default value of integer_const1 is 0, integer_const2 is 1, and so on. We can also change the default value of the integer constants at the time of the declaration.

For example:

The default value of mango is 0, apple is 1, strawberry is 2, and papaya is 3. If we want to change these default values, then we can do as given below:

Enumerated type declaration

As we know that in C language, we need to declare the variable of a pre-defined type such as int, float, char, etc. Similarly, we can declare the variable of a user-defined data type, such as enum. Let's see how we can declare the variable of an enum type.

Suppose we create the enum of type status as shown below:

Now, we create the variable of status type:

In the above statement, we have declared the 's' variable of type status.

To create a variable, the above two statements can be written as:

In this case, the default value of false will be equal to 0, and the value of true will be equal to 1.

Let's create a simple program of enum.

In the above code, we create an enum type named as weekdays, and it contains the name of all the seven days. We have assigned 1 value to the Sunday, and all other names will be given a value as the previous value plus one.

Output

Let's demonstrate another example to understand the enum more clearly.

In the above code, we have created a type of enum named as months which consists of all the names of months. We have assigned a '1' value, and all the other months will be given a value as the previous one plus one. Inside the main() method, we have defined a for loop in which we initialize the 'i' variable by jan, and this loop will iterate till December.

Output

Why do we use enum?

The enum is used when we want our variable to have only a set of values. For example, we create a direction variable. As we know that four directions exist (North, South, East, West), so this direction variable will have four possible values. But the variable can hold only one value at a time. If we try to provide some different value to this variable, then it will throw the compilation error.

The enum is also used in a switch case statement in which we pass the enum variable in a switch parenthesis. It ensures that the value of the case block should be defined in an enum.

Let's see how we can use an enum in a switch case statement.

Output

Some important points related to enum

• The enum names available in an enum type can have the same value. Let's look at the example.

Output

• If we do not provide any value to the enum names, then the compiler will automatically assign the default values to the enum names starting from 0.
• We can also provide the values to the enum name in any order, and the unassigned names will get the default value as the previous one plus one.
• The values assigned to the enum names must be integral constant, i.e., it should not be of other types such string, float, etc.
• All the enum names must be unique in their scope, i.e., if we define two enum having same scope, then these two enums should have different enum names otherwise compiler will throw an error.

Let's understand this scenario through an example.

Output

• In enumeration, we can define an enumerated data type without the name also.

Output

Enum vs. Macro in C

• Macro can also be used to define the name constants, but in case of an enum, all the name constants can be grouped together in a single statement.
  For example,
  
  # define pass 0;
  # define success 1;
  
  The above two statements can be written in a single statement by using the enum type.
  enum status{pass, success};
• The enum type follows the scope rules while macro does not follow the scope rules.
• In Enum, if we do not assign the values to the enum names, then the compiler will automatically assign the default value to the enum names. But, in the case of macro, the values need to be explicitly assigned.
• The type of enum in C is an integer, but the type of macro can be of any type.