Greetings, and welcome to the forums. I can see you're new, and I'd like to let you know we're a diverse group of professionals and students who like to ask and answer questions. You've asked the same question three times, and I'm sorry you haven't received an answer yet. But your question, is so general, there is no answer we can really give, unless we write a textbook, one letter at a time, and no one wants to do that. So please, try to find and read some online resources for your topic, or check a university library for some general text on the subject, then come back with some more specific questions.