NEXTSTEP is the original object-oriented, multitasking operating system that NeXT Computer, Inc. developed to run on its proprietary NeXT computers (informally known as black boxes ). NEXTSTEP 1.0 was released on 18 September 1989 after several previews starting in 1986, and the last release 3.3 in early 1995, by which time it ran not only on Motorola 68000 family processors (specifically the original black boxes), but also generic IBM compatible x86/Intel, Sun SPARC, and HP PA-RISC. About the time of the 3.2 release NeXT teamed up with Sun Microsystems to develop OpenStep, a cross-platform standard and implementation (for Sun Solaris, Microsoft Windows, and NeXT s version of the Mach kernel) based on NEXTSTEP 3.2.
On February 4, 1997 Apple Computer acquired NeXT for $427 million, using the OpenStep operating system as the basis for Mac OS X. Traces of the NEXTSTEP/OpenStep heritage can still be seen in Mac OS X; for example, in the Cocoa development environment, the Objective-C library classes have NS prefixes, and the HISTORY section of the manual page for the defaults command in Mac OS X straightforwardly states that the command First appeared in NeXTStep. A free software implementation of the OpenStep standard, GNUstep, also exists.