Advice for programming
1. Test your code with several valid inputs. If the user is asked to enter a number of items to order, you may try order 3 items and 100 items, and possibly 0 items. If your program is required to test for invalid orders, also try to buy -10 items.

2. Take an incremental approach to your work. Code a little, test a little. Save already-working code as backup in separate C++ files before building on it to make the larger final code.

3. While debugging, it may be helpful for you to include extra cout statements telling you the value of different variables across the runtime of the program.

4. Be careful with every character you type. In case of compile-errors, check for misspelled words, missing semi-colons, unbalanced parentheses and braces (e.g., a { without a } later in the code.)

5. Declare your variables and use proper variable types for the required tasks

6. Use proper style: good use of spacing, comments, and meaningful variable names