Question

Use a preprocessor directive to define the value of PI (π), then calculate the area of a circle using PI, given any radius value (r).

Answer 1

The pre-processor processes our program before going to the compiler. It begins with a hash symbol (#).

I'm using C++ to write the program.

#include<iostream>
using namespace std;
//using preprocessor directive for defining value of PI
#define PI 3.141926
#include<math.h> // for finding power of a number
int main(){
float r, Area;
cout<<"Enter Radius of the circle: ";
cin>>r;
Area= PI* pow(r, 2); // pow(r,2)== r^2
cout<<"Area of the circle is: "<< Area;
return 0;
}
Output:

In this program we are defining the value of PI using "define" preprocessor directive. After taking input value for radius (r) i've calculated Area. Finally i'm printing the Area