osprog.cpp

// C++ Program to compute the area of a circle
#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    // Variables to hold the radius and area
    float radius, area;
    
    // Open file
    ofstream file;
    file.open("result.txt", ofstream::out | ofstream::app);
    
    // Get the radius of the circle from the user
    cout << "Enter the radius of the circle: ";
    cin >> radius;
    
    // Calculate the area of the cirlce
    area = 3.14 * radius * radius;
    
    // Output
    cout << "Area of circle with radius " << radius << " is " << area << endl;
    file << "Area of circle with radius " << radius << " is " << area << endl;

    // Close the file 
    file.close();

    return 0;
}