cocoa.h doesn't exist

I am new to Mac development and just downloaded Mountain Lion and Xcode 4.4.1. When I try to follow the "getting started" example or simply download and try to run any of the example code projects I get the error "Cocoa/Cocoa.h file not found". I have searched for cocoa.h in my computer with no success. XCode gives its path as /System/Library/Frameworks/Cocoa.framework but when I go there and look in Versions/A I find nothing. Where do I obtain this file?