 The heritage of Darwin began with NeXT's NeXTSTEP operating system (later, since version 4.0, known as OPENSTEP), first released in 1989.After Apple bought NeXT in 1997, it announced it would base its next operating system on OPENSTEP.This was developed into Rhapsody in 1997, Mac OS X Server 1.0 in 1999, Mac OS X Public Beta in 2000, and Mac OS X 10.0 in 2001.