C++ program to find area of the circle

In this example, you will learn about C++ program to find area of the circle with and without using the function.

Formula to find area of the circle:

Area_circle = Π * r * r

where,

mathematical value of Π is 3.14159.

Let’s calculate the are of the circle using two methods.

Example: C++ program to find area of the circle.

//C++ program to calculate area of the circle
#include <iostream>
using namespace std;

 int main() {
   float radius, area_circle;

   // take radius as input
   cout << "Enter the radius of circle: ";
   cin >> radius;

   area_circle = 3.14 * radius * radius;
   cout << "Area of circle: " << area_circle << endl;

   return 0;
}

Output

Enter the radius of circle: 5
Area of circle: 78.5

Example: C++ program to find area of the circle using function.

//C++ program to find area of the circle using function
#include <iostream>
using namespace std;

//function declaration
float areaOfCircle(float radius_circle);

int main() {
   float radius;

   // take radius as input
   cout << "Enter the radius of circle: ";
   cin >> radius;

   cout << "Area of circle: " << areaOfCircle(radius) << endl;

   return 0;
}

// function definition to calculate area of circle
float areaOfCircle(float radius_circle)
{
   float area_circle;
   area_circle = 3.14 * radius_circle * radius_circle;

   return area_circle; //return area
 }

Output

Explanation

In the first program, we have simply calculated area of the circle in the main program.

However, we have used areaOfCircle( ) function for calculating area of the circle in the second program.