typedef C

Typedef is a c/c++ programming language reserved keyword. It is used to create a
new name (alias) for existing data types or derived data type. typedef is useful in avoiding naming confusion in large c program.

Syntax

typedef data_type new_name;

Example

void main(){

 typedef float DECIMAL;
 DECIMAL PI = 3.14;
 
}

float is given new and meaningful name DECIMAL, now, in above program, DECIMAL can used in place of float.

When to use Typedef

Use typedef to make complex declaration easier to understand. It makes a large and complex program easier to understand.

With what types Typedef can be used

Typedef can be used with built-in data types, arrays, structs, pointers or functions.

Typedef with primitive data types

void main()
{
	typedef unsigned char  uchar;
	uchar c = 'a';
}

Typedef with Pointers

void main()
{
	typedef  float*  PtrFlt;
	PtrFlt PI = 3.14, CM = 22.57;
}

Typedef with structure

typedef struct {
  int speed;
  int average;
} car;

void main()
{
  typedef car mycar;
  mycar.speed = 20;
  mycar.average = 10;
}

Typedef with Union

typedef union {
  int a;
  int b;
} vehicle;

void main()
{
  typedef vehicle car;
  car.a = 20;
  car.b = 10;
}