NeXTSTEP
NeXTSTEP is a discontinued object-oriented, multitasking operating system based on the Mach kernel and the UNIX-derived BSD. It was developed by NeXT Computer in the late 1980s and early 1990s and was initially used for its range of proprietary workstation computers such as the NeXTcube. It was later ported to several other computer architectures.

Although relatively unsuccessful at the time, it attracted interest from computer scientists and researchers. It was used as the original platform for the development of the Electronic AppWrapper, the first commercial electronic software distribution catalog to collectively manage encryption and provide digital rights for application software and digital media, a forerunner of the modern "app store" concept. It was also the platform on which Tim Berners-Lee created the first web browser, and on which id Software developed the video games Doom and Quake.

In 1996, NeXT was acquired by Apple Computer. The NeXTSTEP platform and OpenStep later became components of the Unix-based architecture of Mac OS X (now macOS) — a successor to the classic Mac OS that leveraged a combination of Unix supplemented by NeXTSTEP components and Apple's own technologies. Unix  derivatives incorporating NeXTSTEP would eventually power all of Apple's platforms, including iPhone.

Overview
NeXTSTEP (also stylized as NeXTstep, NeXTStep, and NEXTSTEP) is a combination of several parts:
 a Unix operating system based on the Mach kernel, plus source code from BSD
 Display PostScript and a proprietary windowing engine
 the Objective-C language and runtime
 an object-oriented (OO) application layer, including several "kits"
 development tools for the OO layers.

NeXTSTEP is notable for having been a preeminent implementation of the latter three items. The toolkits offer considerable power, and are the canonical development system for all of the software on the machine.

It introduced the idea of the Dock (carried through OpenStep and into today's macOS) and the Shelf. NeXTSTEP also originated or innovated a large number of other GUI concepts which became common in other operating systems: 3D "chiseled" widgets, large full-color icons, system-wide drag and drop of a wide range of objects beyond file icons, system-wide piped services, real-time scrolling and window dragging, properties dialog boxes called "inspectors", and window modification notices (such as the saved status of a file). The system is among the first general-purpose user interfaces to handle publishing color standards, transparency, sophisticated sound and music processing (through a Motorola 56000 DSP), advanced graphics primitives, internationalization, and modern typography, in a consistent manner across all applications.

Additional kits were added to the product line to make the system more attractive. These include Portable Distributed Objects (PDO), which allow easy remote invocation, and Enterprise Objects Framework, a powerful object-relational database system. The kits made the system particularly interesting to custom application programmers, and NeXTSTEP had a long history in the financial programming community.

History
A preview release of NeXTSTEP (version 0.8) was shown with the launch of the NeXT Computer on October 12, 1988. The first full release, NeXTSTEP 1.0, shipped on September 18, 1989. The last version, 3.3, was released in early 1995, by which time it ran on not only the Motorola 68000 family processors used in NeXT computers, but also on Intel x86, Sun SPARC, and HP PA-RISC-based systems.

NeXTSTEP was later modified to separate the underlying operating system from the higher-level object libraries. The result was the OpenStep API, which ran on multiple underlying operating systems, including NeXT's own OPENSTEP, Windows NT and Solaris. NeXTSTEP's legacy stands today in the form of its direct descendants, Apple's macOS, iOS, watchOS, and tvOS operating systems.

Unix
From day one, the operating system of NeXTSTEP was built upon Mach/BSD.
 It was initially built on 4.3BSD-Tahoe.
 It changed to 4.3BSD-Reno after the release of NeXTSTEP 3.0.
 It changed to 4.4BSD during the development of Rhapsody.

Legacy
The first web browser, WorldWideWeb, and the first-ever app store were all invented on the NeXTSTEP platform.

Some features and keyboard shortcuts now commonly found in web browsers can be traced back to NeXTSTEP conventions. The basic layout options of HTML 1.0 and 2.0 are attributable to those features available in NeXT's Text class.

Lighthouse Design Ltd. developed  Diagram!, a drawing tool, originally called BLT (for Box-and-Line Tool) in which objects (boxes) are connected together using "smart links" (lines) to construct diagrams such a flow charts. This basic design could be enhanced by the simple addition of new links and new documents, located anywhere in the local area network, that foreshadowed Tim Berners-Lee's initial prototype that was written in NeXTStep (October–December 1990).

In the 1990s, the pioneering PC games Doom (with its WAD level editor), Doom II, and Quake (with its respective level editor) were developed by id Software on NeXT machines. Other games based on the Doom engine such as Heretic and its sequel Hexen by Raven Software as well as Strife by Rogue Entertainment were also developed on NeXT hardware using id's tools.

Altsys made a NeXTSTEP application called Virtuoso, version 2 of which was ported to Mac OS and Windows to become Macromedia FreeHand version 4. The modern "Notebook" interface for Mathematica, and the advanced spreadsheet Lotus Improv, were developed using NeXTSTEP. The software that controlled MCI's Friends and Family calling plan program was developed using NeXTSTEP.

About the time of the release of NeXTSTEP 3.2, NeXT partnered with Sun Microsystems to develop OpenStep. It is the product of an effort to separate the underlying operating system from the higher-level object libraries to create a cross-platform object-oriented API standard derived from NeXTSTEP. The OpenStep API targets multiple underlying operating systems, including NeXT's own OPENSTEP. Implementations of that standard were released for Sun's Solaris, Windows NT, and NeXT's version of the Mach kernel. NeXT's implementation is called "OPENSTEP for Mach" and its first release (4.0) superseded NeXTSTEP 3.3 on NeXT, Sun, and Intel IA-32 systems.

Following an announcement on December 20, 1996, Apple Computer acquired NeXT on February 4, 1997, for $429 million. Based upon the "OPENSTEP for Mach" operating system, and developing the OPENSTEP API to become Cocoa, Apple created the basis of Mac OS X, and eventually, in turn, of iOS/iPadOS, watchOS, and tvOS.

A free software implementation of the OpenStep standard, GNUstep, also exists.

Release history

Versions up to 4.1 are general releases. OPENSTEP 4.2 pre-release 2 is a bug-fix release published by Apple and supported for five years after its September 1997 release.

See also
 OpenStep, the object-oriented application programming interface derived from NeXTSTEP
 GNUstep, an open-source implementation of Cocoa API respectively OpenStep API
 Window Maker, a window manager designed to emulate the NeXT GUI for the X Window System
 Bundle (macOS)
 Miller Columns, the method of directory browsing that NeXTSTEP's File Viewer used
 Multi-architecture binary
 NeXT character set
 Previous, an emulator for NeXT hardware capable of running some versions of NeXTSTEP

References

 http://www.cnet.com/news/ibm-buys-sequent-for-810-million
 A complete guide to the confusing series of names applied to the system

External links
 
 NeXTComputers.org
 
 The Next Step BYTE Magazine 14-03, Object Oriented Programming with NextStep
  A modern NextStep inspired desktop environment.

1989 software
Berkeley Software Distribution
Discontinued operating systems
Mach (kernel)
NeXT
Object-oriented operating systems
Unix variants
Window-based operating systems