A program which logs in users and lets users buy books
A user can log in and buy any books stored in the Book.txt.
The list of users with their balance and password is saved in User.txt file.
If the user gives wrong credentials then the program asks the user for another try.
The user gets three tries, if not yet correct then program closes.
The user chooses the books from the book list which will be visible to him/her on the console.
The user chooses which ever books he wants and then presses Q/q to log out.
The programs adds the cost of all the books and deducts it from the balance of the particular user