C++ Program to compute the area and circumference of a circle

Here, you will learn to find the area and circumference of a circle based on its radius entered by the user at run-time in C++ programming

How to calculate the area and circumference of a circle based on its radius?

The area of a circle is the region occupied by the circle in a two-dimensional plane. It can be determined easily using a formula. area = πr2
The value of π is 3.14. And r indicates the radius of the circle. This formula can also be written as:
area = 3.14*r*r

The perimeter or circumference of a circle is its boundary or the complete arc length of the periphery of a circle
Perimeter of a circle = 2 π r = π D units
where,
•    r = radius of the circle
•    D = diameter of the circle.

C++ program to find the area and circumference of a circle based on its radius

Ask the user to enter the value of the radius of the circle. Read the value to a variable r; Calculate the area using the formula given above
3.14 * r * r
Get the value to the variable area and display it on the screen.
Calculate the value of the perimeter of the circle 
2 * 3.14 * rad;
Get the value to the variable circum and display it on the screen.

Algorithm

Step 1:  Call the header file iostream.

Step 2: Use the namespace std.

Step 3: Open the integer type main function; int main().

Step 4: Declare  float type variables r, area circum;

Step 5: Ask the user to enter the value of the radius of the circle.

Step 6: Get the value of radius to the variable r.

Step 7: Calculate the area using the formula 3.14 * r * r;

Step 8: Get the value to the variable area;

Step 9: Display the result;

Step 10: Calculate the circumference using the formula 2 * 3.14 * r;

Step 11: Get the value to the variable circum;

Step 12: Display the result;

Step 13: Exit


 

C++ Source Code

                                          #include<iostream>
using namespace std;
int main()
{
    float r, area, circum;
    cout<<"Enter the Radius of Circle: ";
    cin>>r;
    area = 3.14*r*r;
    cout<<"\nArea of Circle = "<<area;
    cout<<endl;
    circum = 2*3.14*r;
    cout<<"\nCircumference of Circle = "<<circum;
    cout<<endl;
    return 0;
}
                                      

OUTPUT

Enter the Radius of Circle: 6
Area of Circle = 113.04

Circumference of Circle = 37.68