C Programming code to calculate area of a circle

C Programming code to calculate area of a circle by defining pi as 3.1415
Algorithm

1. Define pi as 3.1415 since pi is not a predefined constant in C
2. Accept the radius of the circle
3. Calculate the area of the circle
4. Display the output

Code
#include<stdio.h>
#include<conio.h>
#define pi 3.1415
void main()
{
clrscr();
int r;
float a;
printf("Enter the radius of a circle. \n");
scanf("%d",&r);
a=pirr;
printf("\n Radius= %d",r);
printf(" \n Area= %f",a);
getch();
}