Objective-C class names begin with capital letters. Multi-word class names capitalize each word, with no underscore separation.
All protocols end with ing .
All collection protocols end with Collecting . Include files that supply function prototypes for other C functions are all lower case. Instance variables begin with an underscore, are all lower case, and have underscores separating their component words. The leading underscore distinguishes them from local varibles defined inside methods. The version number of the collection library.