What does the "NS" prefix to a class name mean in iOS? I notice the "NS" prefix in all the class names in iOS. What does that mean? (e.g NSMutableArray)
It stands for NextSTEP, the operating system that Steve Jobs (caused to be) built after he was evicted from Apple.  Objective-C and the NextSTEP API are the basis of the newer OpenSTEP and MacOS-X APIs.