Please note that this is not a homework site. We won't do your homework for you. The purpose of homework is that you learn by doing. However we are always willing to help solve problems you encountered, correct mistakes you made in your code and answer your questions.
We didn't see your attempts to solve this problem yourself and so we cannot correct mistakes you didn't made and answer questions you didn't ask. To get help you should do something yourself and get real problems with something. If your problem really is "I don't understand a thing", then you should go back to basics and study again.
Even the most complex program is nothing more than a combination of simple pieces. Break your task into smaller pieces. Tackle each separately.
I understand. Do forgive me, it indeed seemed like I was asking for my assignment to be done.
in c/c++ you have to provide include guards to prevent multiple definitions: