Each type has a base directory. Inside this base directory, are subdirectories, which contain the actual code. These subdirectories are named -after the platforms the are compiled on. Unix is also used as a common +after the platforms they are compiled on. Unix is also used as a common directory. If the code you are writing is POSIX based, you should look at the code in the unix directory. A good rule of thumb, is that if more than half your code needs to be ifdef'ed out, and the structures required for your code