This C++ program calculates the area of a circle. It prompts the user to enter the radius, then multiplies it by itself and 3.1425 to calculate the area. Finally, it displays the calculated area to the user.

1. Program to Calculate Area of Circle
#include<iostream>
using namespace std;
int main()
{
float radius;
float area;
cout<<"Enrer Radius of a Circle";
cin>>radius;
area=3.1425*radius*radius;
cout<<"Area of a Circle is "<<area<<endl;
}