C++ Exercises: Find the area and circumference of a circle

Last update on August 11 2025 12:57:28 (UTC/GMT +8 hours)

Area and Circumference of Circle

Write a C++ program to find the area and circumference of a circle.

Visual Presentation:

C++ Exercises: Find the area and circumference of a circle

Sample Solution:

C++ Code :

#include <iostream> // Including the input-output stream header file

#define PI 3.14159 // Defining the constant value of PI

using namespace std; // Using the standard namespace

int main() // Start of the main function
{
    float radius, area, circum; // Declaring floating-point variables for radius, area, and circumference

    cout << "\n\n Find the area and circumference of any circle :\n"; // Outputting a message indicating the calculation of circle area and circumference
    cout << "----------------------------------------------------\n"; // Outputting a separator line

    cout << " Input the radius(1/2 of diameter) of a circle : "; // Prompting the user to input the radius of the circle
    cin >> radius; // Taking input for the radius from the user

    circum = 2 * PI * radius; // Calculating the circumference of the circle: 2 * PI * radius
    area = PI * (radius * radius); // Calculating the area of the circle: PI * radius^2

    cout << " The area of the circle is : " << area << endl; // Displaying the calculated area of the circle
    cout << " The circumference of the circle is : " << circum << endl; // Displaying the calculated circumference of the circle
    cout << endl; // Outputting a blank line for better readability

    return 0; // Returning 0 to indicate successful program execution
} // End of the main function

Sample Output:

 Find the area and circumference of any circle :                       
----------------------------------------------------                   
 Input the radius(1/2 of diameter) of a circle : 5                     
 The area of the circle is : 78.5397                                   
 The circumference of the circle is : 31.4159

Flowchart:

For more Practice: Solve these Related Problems:

Write a C++ program to compute the area and circumference of a circle when given the diameter instead of the radius.
Write a C++ program that calculates the area and circumference of a circle and formats the results to three decimal places.
Write a C++ program to compute the area and circumference of a circle and then compare them to a fixed reference circle.
Write a C++ program that calculates the area and circumference of a circle using a function and then prints a summary report.

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