NeXTSTEP (also written NeXTstep, NeXTStep, and NEXTSTEP) was an object-oriented, multitasking operating system developed by NeXT Computer to run on its range of proprietary workstation computers, such as the NeXTcube. It was later ported to several other computer architectures.

A preview release of NeXTSTEP (version 0.8) was shown at 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 not only on the Motorola 68000 family processors used in NeXT computers, but also 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 OpenStep API, which ran on multiple underlying operating systems, including NeXT's own OPENSTEP. Apple's OS X and iOS are direct descendants of NeXTSTEP, through the OPENSTEP lineage.

Read more about NeXTSTEP:  Description, Influence, Release History