Chapter 5,Problem 1:Object Oriented Programming by Robert Lafore in C++ Solution Manual

//28-11-2014
//Ahmad Furqan Attari
//p5.1
#include <iostream>
#include <conio.h>
using namespace std;
#define PI 3.14159;
float circarea(float r)
{
 return r*r*PI;
}
void main(void)
{
 float r;
 cout << "Enter Radius: ";
 cin >> r;
 cout << "Area of the circle is: " << circarea(r);
 _getch();
}