The Application Kit is a collection of classes within the OpenStep specification and provided by such operating systems as OPENSTEP, GNUstep, and Mac OS X under Cocoa, providing classes oriented around graphical user interface capabilities. An equivalent in Cocoa Touch is UIKit.
Classes
Of the more than 170 classes included in the Application Kit, the following classes form the core:
NSApplication
NSWindow
NSView
NSResponder
References
Application Kit Wikipedia(Text) CC BY-SA