C++ Exercises: Accepts the radius of a circle from the user and compute the area and circumference

Last update on August 11 2025 12:58:18 (UTC/GMT +8 hours)

Circle Area and Circumference

Write a C++ program that accepts the radius of a circle from the user and computes the area and circumference.

Visual Presentation:

C++ Exercises: Accepts the radius of a circle from the user and compute the area and circumference

Sample Solution:

C++ Code :

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

#define PI 3.14159 // Defining a constant PI with the value 3.14159

using namespace std; // Using the standard namespace

int main() // Start of the main function
{
    float radius, area, circum; // Declaring variables to store radius, area, and circumference

    cout << "\n\n Find the area and circumference of any circle :\n"; // Outputting a message indicating the purpose of the program
    cout << "----------------------------------------------------\n"; // Displaying 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; // Reading the radius from the user

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

    cout << " The area of the circle is : " << area << endl; // Outputting the calculated area of the circle
    cout << " The circumference of the circle is : " << circum << endl; // Outputting the calculated circumference of the circle

    cout << endl; // Displaying an empty line for better readability
    return 0; // Return statement indicating successful completion of the program
}

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 that calculates the area and circumference of a circle from the radius input and displays the result with labels.
Write a C++ program to compute the area and circumference of a circle, then compare these values to a given threshold.
Write a C++ program that uses a function to calculate both the area and circumference of a circle and prints the results.
Write a C++ program to input the radius, compute the circle’s area and circumference, and output the results in a formatted report.

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