You probably shouldn't start by making iPhone apps. You need to learn C++ and Cocoa first, start from basics. XCode isn't actually a code, its just an environment for coding, like a program for making other programs, it can support many programming languages, as i listed C++ and Cocoa are the ones you should learn first, especially C++, its the base for most other programming languages. What programming language did you use in Visual Studio? C++, C#?