NSNumber, NSString, etc.

All of these new variable types are Objective-C objects in the Cocoa framework. NSNumber is a class that defines a bunch of different kinds of numbers (similar to int and float). These numbers are more optimized for things like memory and device compatibility. NSString is the Cocoa object for something that doesn't exist in C - a string. In C, you must use a character array for a string, which is definitely not the best way to deal with things. NSString is there to make your life easier when dealing with strings. NSArray is similar to a C array, but it can hold objects (the most common data type in Objective-C), which a C array cannot. All of these objects add various methods and properties that their C counterparts (if they exist) don't have, like NSString's stringByAppendingString:, which creates a new string by putting one string on the end of another.