SCO OpenServer

SCO Open Server 6.x

SCO OpenServer, previously SCO UNIX and SCO Open Desktop (SCO ODT), is a closed source version of the Unix computer operating system developed by Santa Cruz Operation (SCO) and now maintained by the SCO Group.

SCO UNIX was the successor to SCO Xenix, derived from AT&T System V Release 3.2 with an infusion of Xenix device drivers and utilities. SCO UNIX System V/386 Release 3.2.0 was released in 1989 as the commercial successor to SCO Xenix. The base operating system did not include TCP/IP networking or X Window System graphics. Shortly after the release of this bare OS, SCO shipped an integrated product under the name of SCO Open Desktop, or ODT. 1994 saw the release of SCO MPX, an add-on SMP package.

At the same time, AT&T completed its merge of Xenix, BSD, SunOS and System V features into System V Release 4. SCO UNIX remained based on System V Release 3, but eventually added home-grown versions of most of the features of Release 4.

The 1992 releases of SCO UNIX 3.2v4.0 and Open Desktop 2.0 added support for long file names and symbolic links. 1995's rebranded OpenServer Release 5.0.0 added support for ELF executables and dynamically linked shared objects, and made many kernel structures dynamic.

SCO purchased the UnixWare system and its System V Release 4 code base from Novell in 1995. SCO was eventually able to re-use some code from that version of UnixWare in later releases of OpenServer. Until Release 6, this came primarily in the compilation system and the UDI driver framework and the USB subsystem written to it.

By the end of the 1990s, there were around 15,000 value-added resellers (VARs) around the world who provided solutions for customers of SCO's Unix systems.

SCO announced on August 2, 2000 that it would sell its Server Software and Services Divisions, as well as UnixWare and OpenServer technologies, to Caldera Systems, Inc. The purchase was completed in May 2001. The remaining part of the SCO company, the Tarantella Division, changed its name to Tarantella, Inc., while Caldera became Caldera International, and subsequently in 2002 the SCO Group.