A Unix-based operating system originally designed by NeXT for the NeXT computer. NeXTSTEP was also ported to x86, Sun and HP workstations. Renamed OPENSTEP as of Version 4 in 1989, Apple later acquired the company, and the Mach microkernel used in OPENSTEP became the heart of Mac OS X. See
OpenStep,
Darwin,
NeXT and
Mac OS X.