#include<stdio.h>
#include<conio.h>
#define PI 3.141
    
float cal_area(float );
void main()
{
    float redius;
    clrscr();
    printf("\n ENTER RADIOUS:- ");
    scanf("%f",&redius);
    cal_area(redius);
    getch();
}
float cal_area(float r)
{
    float area;
    area = PI*r*r;
    printf("\n THE AREA IS %f",area);
    return(area);
}
    
******************** OUTPUT ***************************

    ENTER RADIOUS:- 5

    THE AREA IS 78.525002

*******************************************************