This question is way down the line for me as I'm only learning my first ever programming language (Objective-C) but something I'm curious about. How do you write apps that you want to use on different devices? For example iPhone 3G S, iPhone 4/4S & iPad 1/2 & 3rd Gen. Some of these devices don't have retina display for example then you have iPads that screens are much better anyway. Do you need to write different versions of your app or what is the process? Thanks in advance.