1969

UNICS

1971

UNIX Time-Sharing System

1978

BSD

1980

XENIX OS

1981

UNIX System III

1982

SunOS

1983

UNIX System V

1986

GNU (Trix)

HP-UX

1987

Minix

1989

NeXTSTEP

SCO UNIX

1990

Solaris

1991

Linux

1993

FreeBSD

1995

OpenBSD

1999

Mac OS X