token_string : is optional but, are used almost every time in program.
E.g.
#define x 2
Whenever x occurs, it is replaced by the token string 2.
Example :
#include <stdio.h>
#define PI 3.1415
int main()
{
int radius;
float area;
printf("Enter the radius : ");
scanf("%d",&radius);
area=PI*radius*radius;
printf("\nArea=%.2f",area);
return 0;
}
Output :
Enter the radius : 2 Area=12.57
