1.2 Building On OpenStep

The standardization on OpenStep also allowed for the creation of several new library packages that were delivered on the OPENSTEP platform. Unlike the operating system as a whole, these packages were designed to run stand-alone on practically any operating system. The idea was to use OpenStep code as a basis for network-wide applications running across different platforms, as opposed to using CORBA or some other system.

Primary among these packages was PDO (Portable Distributed Objects). PDO was essentially an even more "stripped down" version of OpenStep containing only the Foundation Kit technologies, combined with new libraries to provide remote invocation with very little code. Unlike OpenStep which defined an operating system that applications would run in, under PDO the libraries were compiled into the application itself, creating a stand-alone "native" application for a particular platform. PDO was small enough to be easily portable, and versions were released for all major server vendors.

PDO became somewhat infamous in the mid-90's when NeXT staff took to writing in solutions to various CORBA magazine articles in a few lines of code, whereas the original article would fill several pages. Even though using PDO required the installation of a considerable amount of supporting code (Objective-C and the libraries), PDO applications were nevertheless considerably smaller than similar CORBA solutions, typically about 1/2 to 1/3rd the size.

The similar D'OLE provided the same types of services, but presented the resulting objects as DCOM objects, with the goal of allowing programmers to create DCOM services running on high-powered platforms, called from Microsoft Windows applications. For instance one could develop a high-powered financial modelling application using D'OLE, and then call it directly from within Microsoft Excel. When D'OLE was first released, OLE by itself only communicated between applications running on a single machine. PDO enabled NeXT to demonstrate Excel talking to other Microsoft applications across a network before Microsoft themselves were able to implement this functionality.

Another package developed on OpenStep was EOF (Enterprise Objects Framework), a tremendously powerful (for the time) object-relational mapping product. EOF became very popular in the enterprise market, notably in the financial sector where OPENSTEP caused something of a minor revolution.

2 OPENSTEP

NeXT's first operating system was NeXTSTEP, a sophisticated Mach-UNIX based operating system that was ported to run on several architectures ( PA-RISC, SPARC, i386 and 68k). However, NeXT's new direction for NeXTSTEP was to free the operating system libraries from being tied to UNIX and becoming more device independent.

NeXT completed an implementation of OpenStep on their existing Mach-based OS and called it OPENSTEP. It was, for all intents, NeXTSTEP 4.0, and still retained flagship NeXTSTEP technologies (such as DPS, UNIX underpinnings, user interface characteristics like the Dock and Shelf, and so on), and retained the classic NeXTSTEP user interface and styles. OPENSTEP was further improved, in comparison to NeXTSTEP 3.3, with vastly improved driver support – however the environment to actually write drivers was changed with the introduction of the object-oriented DriverKit.

OPENSTEP supported Intel x86, Sun's SPARC and NeXT's own Motorola based 68k architectures, while the HP PA-RISC version was dropped. Unlike the Solaris port, which ran on top of the platform's "native" OS, these versions continued to run on the underlying Mach-based OS used in NeXTSTEP. OPENSTEP became NeXT's primary OS from 1995 on, and was used mainly on the Intel platform. In addition to being a complete OpenStep implementation, the system was delivered with a complete set of NeXTSTEP libraries for backward compatibility. This was an easy thing to do in OpenStep due to library versioning, and OPENSTEP did not suffer in bloat because of it.

3 OPENSTEP Enterprise

NeXT also delivered an implementation running on top of Microsoft Windows NT 4.0 called OPENSTEP Enterprise (often abbreviated OSE). This was an unintentional demonstration on the true nature of the portability of programs created under the OpenStep specification. Programs for OPENSTEP/Mach could be ported to OSE with little difficulty. This allowed their existing customer base to continue using their tools and applications, but running them inside the Windows system which many of them were in the process of switching to. Never a clean match from the UI perspective -- probably due to OPENSTEP's routing of window graphics through the Display Postscript server, which was also ported to Windows -- OSE nevertheless managed to work fairly well and allowed OpenStep to exist for perhaps another year.

OPENSTEP and OSE had two revisions (and one major one that was never released) before NeXT was purchased by Apple in 1997.

4 Rhapsody

Rhapsody was a reworked OPENSTEP for the Mac, and formed the start of the process that resulted in Mac OS X. It is OPENSTEP with the "Classic" interface and could be regarded as OPENSTEP 5. Two versions of Rhapsody were released to developers. The first, Developer Preview 1, ran only on Intel hardware. The second revision, DP2, was the first version to include support for limited set of Mac hardware.

5 Mac OS X

Since Apple has merged with NeXT, OPENSTEP has became the basis for their new operating system, Mac OS X. Mac OS X's new programming environment is essentially OpenStep (with certain additions such as XML property lists and URL classes for Internet connections) with Mac OS X ports of the development libraries and tools -- this became Cocoa. Mac OS X is essentially OPENSTEP 5/6 (an operating system named Rhapsody, with the "Classic" interface and OPENSTEP under the surface could be regarded as OPENSTEP 5). As Mac OS X, OPENSTEP managed to become the most used Unix in the world.

6 GNUStep

GNUStep was suggested at the time of NeXTSTEP (predating OPENSTEP).

With OPENSTEP and OSE being purchased by Apple, who effectively ended the commercial development of implementing OpenStep for other platforms, GNUstep is an ongoing open source project aiming to create a free software implementation of the OPENSTEP libraries to Linux/Unix based systems.

It has created a lot of work and interest, and is partially functional with its Foundation and AppKit implementations. However the Display PostScript aspect still proves to be problematic, and there has been interest in using Ghostscript as the display engine — effectively "Display Ghostscript".

See GNUstep for more details.

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