OS/X is built on a BSD kernel and designed for PowerPC and G5 systems. It's server applications are varied, from workgroup servers, through video render farms to a supercomputer node. A workstation version comes standard on Apple's desktop machines.

BSD (Berkeley Software Design) is a direct descendant of the UNIX operating system dating back to work done by Sun's co-founder Bill Joy in the late '70s.

HP-UX from Hewlett-Packard, is 64-bit UNIX for PA-RISC and Intel Itanium based systems. It is available in several configurations, each tailored for specific applications from databases to web serving.

AIX is an open UNIX operating environment from IBM. Advanced features such as Dynamic Logical Partitioning provides flexibility and scalability.

OS/390 and the newer Z/OS are IBM's flagship mainframe operating systems. They are made up of many elements and features including Websphere and DB2.

OS/400, designed for IBM's AS/400 (now known as the iSeries) to provide a complete solution. OS/400 includes Websphere, DB2 and everything else needed to run an enterprise business.

Linux is a free Unix-type operating system released under the GNU General Public License. Based on the kernel originally created by Linus Torvalds, it is now one of the most popular server platforms in use.

Microsoft Windows is the most popular operating system in use today. 32-bit and 64-bit versions are available configured for any application from web hosting to enterprise databases.

The IRIX operating system is a high-performance 64-bit operating system based on industry-standard UNIX. IRIX is currently at version 6.5 and is SGI's fifth generation of IRIX.

Sun Microsystem's Solaris is a 64-bit UNIX based operating system available for both SPARC processor-based systems and x86 based systems.

HP OpenVMS (originally from Digital Equipment Co.) is designed for Alpha based systems. Features include high-availability, scalability, and industry-leading cluster technology for large-scale SMP systems.