// reading from a file and writing to a file in append mode

#include <fstream>
#include <iostream>
using namespace std;

int main()
{
	double pricePerBook = 0.0;	
	int numBooks = 0;
	double totalPrice = 0.0;

	ifstream infile("C:/Documents and Settings/PSU_USERNAME/Desktop/data.txt");
	infile >> pricePerBook;
	infile.close();

	cout << "How many books? ";
	cin >> numBooks;

	double bookSubtotal = pricePerBook * numBooks;
	cout << "Your total price is $" << bookSubtotal << endl;

	ofstream outfile("C:/Documents and Settings/PSU_USERNAME/Desktop/output.txt", ios::app); // append mode
	outfile << bookSubtotal << endl;

	outfile.close();

	return 0;
}// end of main