Unix or UNIX is a general-purpose multi-user operating system developed mostly by Ken Thompson and Dennis Ritchie during 1969 at Bell Labs. About one year later during the early 1970s UNIX was unveiled to the general public. The original goal as it is today was to create a stable, secure, and powerful operating system that is portable to many different hardware platforms.
Today UNIX has evolved into three main categories which all flavors of UNIX derive from: BSD (Berkley Software Distribution), System V Release 4, and hybrid. Some of the most poplar flavors of UNIX are: IBM’s AIX, Sun Microsystems' Solaris, SGI’s IRIX, Linux, OpenBSD, and FreeBSD.
- Unix File and Directory Permissions and Modes, by Wayne Pollock, 2001