Using C constant

Program to demonstrate constant

 We will write a program to calculate area of circle using constant value for pi

 #include<stdio.h>
 const float pi= 3.14;       // const value of pi that will never change
 void main()
 {
   float area=1.0,radius=1.0;   // variables require for calculation
   clrscr(); // removing garbage of screen
   printf("Enter radius:"); // ask  for radius value
   scanf("%f",&radius); // accept radius
   area=pi*radius*radius; // calculate area
   printf("\n area = %f ",area);// display result
   getch(); // hold screen until user press any key
 }

Output :