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

October 20, 2023, Learn eTutorial
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## How to calculate the area and circumference of a circle, given radius?

The area of a circle is the space that the circle's closed shape takes, It can be calculated by using a formula.

Area = π r2  or area = 3.14*r*r

where

• the value of π is 3.14.

The perimeter or the circumference is the circle's boundary length.

The perimeter = 2 π r or can be written as pi D

where,

• D = diameter

## How to find the Area and perimeter of a circle using C++?

In the C++ program, Start with the user entering the value of the radius of the circle. Read the value to a variable r. Then calculate the area using the formula given above  Area = 3.14 * r * r, Now display the value of Area.

Calculate the value of the perimeter using the formula Perimeter = 2 * 3.14 * r Finally display the value of the perimeter for the user.

### Algorithm

Step 1:  Call the header file `iostream`.

Step 2: Use the `namespace std`.

Step 3: Open the 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 the 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
```

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