Cocoa

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CHAPTER 1 : INTRODUCTION
Cocoa is an application environment for both the Mac OS X operating system and iPhone OS, the operating system used on multi-touch devices such as iPhone and iPod touch. It consists of a suite of object-oriented software libraries, a runtime, and an integrated development environment
The Cocoa Environment
Cocoa is a set of object-oriented frameworks that provides a runtime environment for applications running on Mac OS X and iPhone OS. It is also part of a development environment that helps you efficiently bring these applications from design stage to deployment. Cocoa is the preeminent application environment for Mac OS X and the only application environment for iPhone OS. (Carbon is an alternative environment on Mac
OS X, but it is a compatibility framework with procedural programmatic interface intended to support existing Mac OS X code bases.) Most of the applications you see on Mac OS X and iPhone OS, including Mail and Safari, are Cocoa applications. An integrated development environment called Xcode supports application development for both platforms. The combination of this development environment and Cocoa makes it easy to create a well-factored, full-featured application.
Introducing Cocoa
As with all application environments, Cocoa presents two faces; it has a runtime aspect and a development aspect. In its runtime aspect, Cocoa applications present the user inter face and are tightly integrated with the other visible portions of the operating system; on Mac OS X, these include the Finder, the Dock, and other applications from all environments. But it is the development aspect that is the more interesting one to programmers. Cocoa is an integrated suite of object-oriented software components—classes—that enables you to rapidly create robust, full-featured Mac OS X applications. These classes are reusable and adaptable software building blocks; you can use them as-is or extend them for your specific requirements. Cocoa classes exist for just about every conceivable development necessity, from user-inter face objects to data formatting, and where a need hasn’t been anticipated, you can easily create a subclass of an existing class that answers that need.
Cocoa history
Cocoa is the continuation of several frameworks (primarily the App Kit and Foundation Kit) from the NeXTSTEP and OPENSTEP programming environments developed by NeXT in the 1980s and 1990s. Apple acquired NeXT in December 1996, and subsequently went to work on the Rhapsody operating system that was supposed to be the direct successor of OPENSTEP. It was to have had an emulation base for Mac OS applications, called Blue Box. The OPENSTEP base of libraries and binary support was termed Yellow Box. Rhapsody evolved into Mac OS X, and the Yellow Box became Cocoa. As a result, Cocoa classes begin with the acronym "NS" (standing either for the NeXT-Sun creation of OPENSTEP, or for the
original proprietary term for the OPENSTEP framework, NeXTSTEP): NSString, NSArray, etc. Much of the work that went into developing OPENSTEP was applied to the development of Mac OS X, Cocoa being the most visible part. There are, however, some differences. For example, NeXTSTEP and OPENSTEP used Display PostScript for on-screen display of text and graphics, while Cocoa depends on Apple's Quartz (which uses the PDF imaging model). Cocoa also has a level of Internet support, including the NSURL and WebKit HTML classes, and others, while under OPENSTEP there was only rudimentary support for managed network connections through NSFileHandle classes and Berkeley sockets.
Prior to its current use, the "Cocoa" trademark was the name of an application that allowed children to create multimedia projects. It was originally known as KidSim, and is now licensed to a third party and marketed as Stagecast Creator. The program was discontinued in one of the rationalizations that followed Steve Jobs' return to Apple. The name was re-used to avoid the delay while registering a new trademark, with Stagecast agreeing to market the older Cocoa under a new name.