“Typedef” Data Type in C Language with Free Notes

Typedef

In addition to the simple data types, such as integer, float, char, etc., C allows the users to declare new data types called user defined data types. These data type can be declared with the help of a keyword called Typedef whose general form is given below,

typedef<type><new_type>;

Where typedef -> is a reserved word, <type> -> is the desired user defined data type. <new_type> -> is the desired used defined data type.

For Example, consider the following declaration,

typdef float abc;

In this declaration, an existing data type (float) has been redefined as abc. Now the user can use as a synonym for the type float as a new type as shown below: –

abc x, y;

In fact this declaration is equivalent to the following: –

float x, y;

It has a limitation that user will have to remember abc as a new type whereas its equivalent float type is already available.

Free Notes PDF

But this utility of typedef is used where the name of a particular type is very long.

e.g. 
struct employee
{ 
    char name[20];
    int age;
    float salary;
};
typedef struct employee emp; // New data type emp defined by the user
emp e1, e2, e3;

For Example, the declaration: –

typedef int age;

can be used to increase the clarity of code as shown below: –

age boy, girl;

For Example; the declaration

typedef float lists[20];
lists bpay, sal, gsal;

these statements are equivalent to

float bpay[20], sal[20], gsal[20];

NOTE: – <typedef> is extremely useful for shortening the long and inconvenient structure declaration in C Language.