With your original question in mind, I think all of the responses, answered your question. Even the responses about schools and books, since these are vital resources that GIVE information about your question and the business you are trying to work.
If you want to setup a POS system, its a different question, than you originally asked. I suggest you reread each of the answers and if you have a new question, you may want to start another topic with another question. RJF