creating modules in C#

Question

hi everybody...
i have a project but i want to make everything clear in my mind before starting coding..actually i am beginner in c# and i want to learn it well...and my problem is that for example in my project i will have some parts like personel or simple account part and etc.. i think about if some companies want personel part but not account so what will happen...should i program them like modules ?...if so how can i create a module or are there some other ways ?
can u inform me about it pls ? or u have any link to share with me ?