C++ program to find the area and perimeter of circle

In this example, we will find the C++ Program to Find Area and Circumference of circle when radius is given.

Area of Circle :- Area of any circle is the region enclosed by the circle itself or the space covered by the circle.

Circumference of a circle :- Circumference of the circle or perimeter of the circle is the measurement of the boundary of the circle.

Formulae :- 

Circumference of Circle – 2ℼr 

 Area of Circle – ℼr² (where r is the radius of circle) and ℼ = 3.14

C++ program to find the area and perimeter of circle

// Program to input (1 or 2). If choice is 1, print the area of 
// a circle otherwise print the perimeter of circle. 
// Accept the radius of circle from user

using namespace std;

#include<iostream>

int main()
{
    const float pi = 3.14;
    float r, area, c;
    int ch;
    
    cout<<"Enter the radius of circle: "<<endl;
    cin>>r;
    cout<<"\t\tOptions"<<endl;
    cout<<"\t1. Area of circle"<<endl;
    cout<<"\t2. perimeter of circle"<<endl;
    cout<<"enter your choice: ";
    cin>>ch;
    switch(ch)
    {
        case 1:
            area = pi*r*r;
            cout<<"radius is:"<<r<<endl;
            cout<<"area is:"<<area<<endl;
            break;
        case 2:
            c = 2*pi*r;
            cout<<"radius is:"<<r<<endl;
            cout<<"perimeter is:"<<c<<endl;
            break;
        default:
            cout<<"invalid choice, try again"<<endl;
            break;
    }
    return 0;
}

Output :-