C++ Object-Oriented Programming: Circle class

Last update on December 20 2024 12:31:06 (UTC/GMT +8 hours)

Write a C++ program to implement a class called Circle that has private member variables for radius. Include member functions to calculate the circle's area and circumference.

Sample Solution:

C Code:

#include <iostream> // Include necessary header for input/output stream

#include <cmath> // Include necessary header for mathematical functions

const double PI = 3.14159; // Define the value of PI as a constant

class Circle { // Define a class named Circle
  private: 
    double radius; // Private member to store the radius

  public:
    // Constructor to initialize the Circle object with a radius
    Circle(double rad): radius(rad) {}

    // Member function to calculate the area of the circle
    double calculateArea() {
      return PI * pow(radius, 2); // Formula to calculate the area of a circle
    }

    // Member function to calculate the circumference of the circle
    double calculateCircumference() {
      return 2 * PI * radius; // Formula to calculate the circumference of a circle
    }
};

int main() {
  // Create a circle object
  double radius;
  std::cout << "Input the radius of the circle: ";
  std::cin >> radius; // Input the radius from the user
  Circle circle(radius); // Create a Circle object with the given radius

  // Calculate and display the area of the circle
  double area = circle.calculateArea(); // Calculate the area using the Circle object
  std::cout << "Area: " << area << std::endl; // Output the calculated area

  // Calculate and display the circumference of the circle
  double circumference = circle.calculateCircumference(); // Calculate the circumference using the Circle object
  std::cout << "Circumference: " << circumference << std::endl; // Output the calculated circumference

  return 0; // Return 0 to indicate successful completion
}

Sample Output:

Input the radius of the circle: 5.2
Area: 84.9486
Circumference: 32.6725

Input the radius of the circle: 4
Area: 50.2654
Circumference: 25.1327

Explanation:

In the above exercise,

const double PI = 3.14159;: This code defines a constant variable PI and assigns it the value of pi (approximately 3.14159).
class Circle { ... }: This block defines a class named Circle. It has a private member variable radius to store the circle radius.
Circle(double rad) : radius(rad) { }: This is the constructor of the Circle class. It takes a parameter rad and initializes the radius member variable with the given value.
double calculateArea() { ... }: This member function calculates the circle area using the formula PI * radius^2. It returns the calculated area.
double calculateCircumference() { ... }: This member function calculates the circumference of the circle using the formula 2 * PI * radius. It returns the calculated circumference.
In the main() function, the program prompts the user to input the circle radius using std::cout and std::cin. It creates a Circle object by calling the constructor with the input radius.
It then calls the calculateArea() and calculateCircumference() member functions on the Circle object to compute the area and circumference.

Flowchart:

CPP Code Editor:

Contribute your code and comments through Disqus.

Previous C++ Exercise: C++ Object oriented programming Exercises Home.
Next C++ Exercise: Rectangle class.