cocoa application kit

Cocoa provides a rich layer of functionality on which you can build applications. Its comprehensive object-oriented API complements a large number of technologies that Mac OS X provides. Some of these technologies are inherited from the NeXTSTEP operating system. Others are based on the BSD Unix heritage of Mac OS X’s core. Still others come from the original Macintosh environment and have been updated to work with a modern operating system. In many cases, you take advantage of these underlying technologies transparently, and you get the use of them essentially “for free.” In some cases, you might use these technologies directly, but because of the way Cocoa is structured, they are a simple and direct API call away.