UNIX operating systems are widely used in both servers and desktop computers. The UNIX environment and its client-server program model have been essential elements in the development of the Internet and the reshaping of computing as centered in networks rather than in individual computers.
Mac OS X Server, which runs the EServer, is a variant of UNIX built on technology that had been developed at NeXT? through the second half of the 1980s and up until Apple purchased the company in early 1997. That, in turn, is based upon the Berkeley Systems Distribution (BSD) UNIX.