Everything about Xenix totally explained
Xenix is a version of the
Unix operating system, licensed by
Microsoft from
AT&T in the late 1970s. The
Santa Cruz Operation (SCO) later acquired exclusive rights to the software, and eventually began distributing it as
SCO UNIX.
History
Xenix was Microsoft's version of Unix intended for use on microcomputers; since Microsoft wasn't able to license the "UNIX" name itself, they gave it an original name. The -ix ending follows a convention used by many other
Unix-like operating systems.
Microsoft purchased a license for
Version 7 Unix from AT&T in 1979, and announced on August 25, 1980 that it would make it available for the
16-bit microcomputer market. The initial development of Xenix was done by
Human Computing Resources Corporation of
Toronto,
Canada. The initial
port of Xenix to the
Intel 8086/8088 architecture was performed by
The Santa Cruz Operation.
Xenix varied from its 7th Edition origins by incorporating elements from
BSD, and soon possessed the most widely installed base of any Unix flavour due to the popularity of the inexpensive
x86 processor.
Microsoft didn't sell Xenix directly to end users; instead, they licensed it to software OEMs such as Intel, Tandy, Altos and SCO, who then
ported it to their own proprietary
computer architectures. Microsoft Xenix originally ran on the
PDP-11; the first
port was for the
Zilog Z8001 16-bit
processor.
Altos shipped a version for their
Intel 8086 based computers early in 1982, Tandy Corporation shipped
TRS-XENIX for their
68000-based systems in January 1983, and SCO released their port to the
IBM PC in September 1983. A port to the 68000-based
Apple Lisa also existed. At the time, Xenix was based on AT&T's
UNIX System III.
Version 2.0 of Xenix was released in 1985 and was based on
UNIX System V. An update numbered 2.1.1 added support for the
Intel 80286 processor. Subsequent releases improved System V compatibility.
In
1986,
SCO ported Xenix to the
386 processor, a
32-bit chip. Xenix 2.3.1 introduced support for i386,
SCSI and
TCP/IP.
When Microsoft entered into an agreement with
IBM to develop
OS/2, it lost interest in promoting Xenix. In 1987 Microsoft transferred ownership of Xenix to SCO in an agreement that left Microsoft owning 25% of SCO. When Microsoft eventually lost interest in OS/2 as well, it based its further high-end strategy on
Windows NT.
Microsoft continued to use Xenix internally, submitting a patch to support functionality in UNIX to AT&T in
1987, which trickled down to the code base of both Xenix and SCO UNIX. Microsoft is said to have used Xenix on
Sun workstations and
VAX minicomputers extensively within their company as late as
1992.
In the late
1980s, Xenix was, according to
The Design and Implementation of the 4.3BSD UNIX Operating System, "probably the most widespread version of the UNIX operating system, according to the number of machines on which it runs".
SCO branched Xenix into
SCO UNIX in 1989. In the meantime, AT&T completed its merge of Xenix, BSD,
SunOS and
System V into
System V Release 4. SCO UNIX was still based on
System V Release 3, but had most features of Release 4. The last version of Xenix itself was 2.3.4.
Trusted Xenix
Trusted Xenix was a variant developed by
Trusted Information Systems which incorporated the
Bell-LaPadula model of multilevel security, and had a multilevel secure interface for the
STU-III secure communications device (that is, an STU-III connection would only be made available to applications running at the same privilege level as the key loaded in the STU-III). It was evaluated by
formal methods and achieved a B2 security rating under the
NSA's
Trusted Computer System Evaluation Criteria—the second highest rating ever achieved by an evaluated operating system. Version 2.0 was released in January 1991, version 3.0 in April 1992, and version 4.0 in September 1993. It was still in use at least as of 1995.
Further Information
Get more info on 'Xenix'.
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