Do you want to learn C or make stuff for X-Plane? I'm obviously biased, but you have a long hard road cut out for yourself. If there's something in mind that you want to make and you need some pointers I'd be happy to kick-start you into Gizmo scripting... If there's something you want to do, but can't do in Gizmo, I'd love to hear about that... I don't think C/C++ is a language worth learning unless you have very specific aims in mind. Python is far more useful for all but the lowest level tasks. That said... With your error, you want to add a Framework to your project, specifically the OpenGL.framework, you should be able to find it in /Library/Frameworks/ I believe. The menus / process to add it in Xcode should be easy enough. (Expect to be fighting these obscure error messages for quite some time.)