The following program reads data from the standard input into a Sales_item object and writes that Sales_item back onto the standard output

#include <iostream>
#include "Sales_item.h"
int main()
{
Sales_item book;
// read ISBN, number of copies sold, and sales price
std::cin >> book;
// write ISBN, number of copies sold, total revenue, and average price
std::cout << book << std::endl;
return 0;
}

Output:

0-201-70353-X 4 24.99
0-201-70353-X 4 99.96 24.99