In C programming, a typedef declaration is used to create shorter, more meaningful, and convenient names for keywords already defined by C like int, float, and char.

What is a typedef in C?

A typedef is a keyword that is used to assign alternative names to existing datatypes. We use typedef with user-defined datatypes when the names of the datatypes become slightly complicated to use in programs. Typedefs can be used to:

• Make a more complex definition reusable by abbreviating it to something less complex.
• Provide more clarity to the code.
• Make it easier to change the underlying data types that we use.
• Make the code more clear and easier to modify.

Following is the syntax for using typedef:

typedef <previous_name> <alias_name>

For example, we would often want to create a variable of type unsigned long. But, then it becomes a complex task if the need to declare an unsigned long comes for multiple variables. To overcome this problem, we use a typedef keyword. Here is how we use it:

#include <stdio.h>
typedef unsigned long ul;
 
int main()
{
    ul a;
}

Applications of Typedef

There are various applications of typedef. Listed below are a few applications of typedef:

• The typedef can be used with arrays, primarily multi-dimensional arrays. It increases the readability of the program.
• Typedefs can also be implemented for defining a user-defined data type like structs or unions with a specific name and type.

Here’s how we use typedefs for defining a struct in C:

typedef struct
{
    structure element1;
    structure element2;
    structure element3;
} name_of_type;

typedef can be used for providing a pseudo name to pointer variables as well.

typedef int *ptr;

Advantages of Typedef

• Typedef, as mentioned, increases the readability of the code. If we are using structures, function pointers, or long keywords repeatedly in our code, then using typedefs increases the readability of the code.
• With the help of typedef, we can use the same name for different applications even in different scopes.
• In the case of structures, if we use the typedef, then we do not require to write the struct keyword at the time of variable declaration.
• Typedef increases the portability of the code.