IRIX is a version of the Unix operating system developed and distributed by Silicon Graphics (SGI) for use on its various computer systems.
IRIX is derived from four main sources: AT&T, Berkeley, MIPS Computer Systems, and Sun Microsystems.
Note: Much of what is discussed here is also applicable to other Unix and Unix-based systems. When the word Unix is used it is understood to apply to Unix systems in general. The word IRIX will be used whenever we are talking about SGI IRIX in particular.