Editing Cocoa (API) (section)

==Main frameworks==
Cocoa consists of three [[Objective-C]] object libraries called ''[[Application framework|frameworks]]''. Frameworks are functionally similar to [[Library (computer science)|shared libraries]], a compiled object that can be dynamically loaded into a program's address space at runtime, but frameworks add associated resources, header files, and documentation.  The Cocoa frameworks are implemented as a type of [[bundle (macOS)|bundle]], containing the aforementioned items in standard locations.

* ''[[Foundation Kit]]'' (''Foundation''), first appeared in Enterprise Objects Framework on NeXTSTEP 3.<ref>[http://www.cilinder.be/docs/next/NeXTStep/3.3/nd/Foundation/HybridWorld.htmld/index.html HybridWorld]. Cilinder.be. Retrieved on September 18, 2013.</ref> It was developed as part of the OpenStep work, and subsequently became the basis for OpenStep's AppKit when that system was released in 1994. On macOS, Foundation is based on [[Core Foundation]]. Foundation is a generic object-oriented library providing [[string (computer science)|string]] and value manipulation, [[container (data structure)|containers]] and [[iteration]], [[distributed computing]], [[event loop]]s (run loops), and other functions that are not directly tied to the graphical user interface. The "NS" prefix, used for all classes and [[constant (programming)|constants]] in the framework, comes from Cocoa's OPENSTEP heritage, which was jointly developed by NeXT and [[Sun Microsystems]].
* ''[[Application Kit]]'' (''AppKit'') is directly descended from the original NeXTSTEP Application Kit. It contains code programs can use to create and interact with [[graphical user interface]]s. AppKit is built on top of Foundation, and uses the same ''NS'' prefix.
* ''[[Core Data]]'' is the object persistence framework included with Foundation and Cocoa and found in Cocoa.h.<ref name="apple1"/>

A key part of the Cocoa architecture is its comprehensive views model. This is organized along conventional lines for an application framework, but is based on the [[Portable Document Format]] (PDF) drawing model provided by [[Quartz (graphics layer)|Quartz]]. This allows creating custom drawing content using [[PostScript]]-like drawing commands, which also allows automatic printer support and so forth. Since the Cocoa framework manages all the clipping, scrolling, scaling and other chores of drawing graphics, the programmer is freed from implementing basic infrastructure and can concentrate on the unique aspects of an application's content.