The Free On-line Dictionary of Computing (30 December 2018):

NEXTSTEP

    The original multitasking operating
   system that NeXT, Inc. developed to run on its proprietary
   NeXT computers (informally known as "black boxes").
   NEXTSTEP includes a specific graphical user interface, an
   interface builder, object-oriented application builder, and
   several "kits" of prebuilt software objects such as the
   Indexing Kit for databases.  This software runs on top of
   NeXT's version of the Mach operating system on NeXT,
   486, Pentium, HP-PA, and Sun SPARC computers.

   The official spelling changed from "NeXTstep" to "NeXTStep" to
   "NeXTSTEP", and finally "NEXTSTEP".

   The last release of NEXTSTEP was 3.3, which NeXT then
   developed into "OpenStep".

   TjL's Pages (http://peak.org/~luomat/).
   Peanuts (http://peanuts.org/peanuts/NEXTSTEP/).

   See also: GNUStep.

   (2003-05-23)