Thank you for your advancing helping.
I do have a problem in how to encode a bank account that has :
1. account number,user name , intial deposit and balance (updatable)
2. that a specific user can see his balance
3. a user can withdraw money
4. a user is deleted when he/she is shifting to other bank.
My instructer obligized me only to encode by using file processing but as you fit with c or c++.
it is better if no longer than three days.