Introduction - If you have any usage issues, please Google them yourself
Asked to use object-oriented ideology. The system includes the following basic functions: (1) create a variety of products, each with a certain amount for the transaction (2) there is commonality between the products, but the code and price are different, maybe there are other different (3) a transaction process comprising: a user selection of goods and quantity, the system gives the price, user payments, the system determines whether the supply of adequate, inadequate or prompt payments, or back to looking for change, etc., enough to supply enough of the nature and amount of the ship (4) can always check the transaction details, can be a period of time, it can last 20 pens, or other ranges (5) can always check the product shipments (6) after exiting the program data files should exist , the next time you run the program after each data extracted from the file