IRIX is the System V based Unix Operating System with BSD extensions developed by SGI to run natively on their 32 and 64-bit MIPS architecture workstations and servers.
It is unusual for a current commercial UNIX because it is BSD based, rather than being based on System V. Because of its Unix underpinnings, it is capable of extremely long uptime, and its XFS filesystem regarded to be one of the most advanced journaling file systems in the industry.
IRIX has particularly strong support for 3D graphics, video and high-bandwidth bulk data transfer. So it was one of the first Unix flavors to feature a GUI for the main desktop environment and is currently used widely due to extremely high performance 3D graphics, the computer animation industry and for scientific visualization.
The current major version of IRIX is IRIX 6.5. New minor versions are released every quarter in two variants: a maintenance release that includes only fixes to the original IRIX 6.5 code, and a feature release that includes improvements and enhancements. As of July, 2003, the current minor version of IRIX is IRIX 6.5.20.
Rumors abound that SGI plans to end-of-life it along with MIPS, in favor of Linux on Itanium but as confirmed by SGI engineers on Usenet, this will not happen any time soon.