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Games - OpenStep

OpenStep is an open object-oriented API specification for an object-oriented operating system that uses any modern operating system as its core, principally developed by NeXT. It is important to recognize that while OpenStep is an API specification, OPENSTEP (all capitalized) is a specific implementation of this OpenStep developed by NeXT. While originally built on a Mach-based Unix (such as the core of NeXTSTEP), versions of OPENSTEP were available for Solaris and Windows NT
as well. Furthermore the OPENSTEP libraries (the libraries that shipped with the OPENSTEP operating system) are in fact a superset of the original OpenStep specification.

History

The OpenStep API was created as the result of a 1993 collaboration between NeXT Computer and Sun Microsystems, allowing this cut-down version of NeXT's NeXTSTEP operating system object layers to be run on Sun's Solaris operating system (more specifically, Solaris on SPARC-based hardware). Most of the OpenStep effort was to strip away those portions of NeXTSTEP that depended on Mach or NeXT-specific hardware being present. This resulted in a smaller system that consisted primarily of Display PostScript, the Objective-C runtime and compilers, and the majority of the NeXTSTEP Objective-C libraries. Not included was the basic operating system, or the display system.

The first draft of the API was published by NeXT in summer 1994. Later that year they released an OpenStep compliant version of their flagship operating system NeXTSTEP running on several of their supported platforms and rebranded it OPENSTEP. Confusingly, this OPENSTEP release also ran on Sun SPARC hardware, independent of Solaris. OPENSTEP remained NeXT's primary operating system product until they were purchased by Apple Computer
in 1997. OPENSTEP was then combined with technologies from the existing Mac OS
to produce Mac OS X
.

Sun never seemed terribly interested in the product, likely a result of the NIH syndrome. In fact it's somewhat unclear why they were ever interested, although it appears it was an attempt to "get in" on the object-oriented operating system market before Microsoft released its plans for the object-oriented Cairo
OS (which never happened). Nevertheless they started their port to Solaris some time in 1994, and released it in 1996. When Sun started work on Java just after this point, Solaris OpenStep was never seen again.

Description

The API OpenStep contrasts with the earlier NeXTSTEP primarily in five ways:

  • OpenStep describes only the upper-level libraries and services (like Display PostScript), whereas NeXTSTEP referred to both these libraries and the operating system as well.
  • removal of any code depending entirely on the Mach kernel, so that OpenStep could be run on top of any reasonably powerful operating system.
  • a significant amount of effort was put into making the system "endian-free", an issue NeXT had already faced during a port of NeXTSTEP to the Intel platform.
  • low-level objects such as strings were represented with C data types in NeXTSTEP, whereas in OpenStep a number of new classes (NSString, NSNumber, etc.) were introduced to support endian-conversion as well as provide added functionality. This had ripple-effects throughout the API, mostly for the better. Other algorithms to deal with low-level data and general fundamental functionality such as key programming algorithms (for example implementing classes to represent array structures (NSArray), and to deal with the processing of files (NSFileHandle)) were changed and made device independent. This set of classes (a framework) was called the Foundation Kit, or just Foundation for short.
  • memory management did evolve from a simple alloc/free mechanism to a new retain/release paradigm: If a piece of code needs to keep an object valid, it retains it, and when it doesn't need it anymore, it releases it.
The API specification itself is comprised of the two main sets of object oriented classes: the GUI and graphics front-end known as the Application Kit, and the aforementioned Foundation Kit.

However, OpenStep also specified the use of Display PostScript, a versatile and powerful PostScript-based method of drawing windows and graphics on screen. NeXT, with its devotion to implementing object-oriented solutions, thought the method of pswraps, interfacing C code to Display PostScript, acted in an encapsulative way and could be thought of its use as being somewhat object oriented like. The Application Kit, Foundation, and Display PostScript comprise the three key technologies in the OpenStep specification; however, Display PostScript was featured in older NeXT technologies, such as NeXTSTEP.

[ Visit the complete Wikipedia entry for OpenStep ]


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