Xenix

SCO XenixMS-XenixTrusted XenixXEDOSXenix operating system
XENIX is a discontinued version of the UNIX operating system for various microcomputer platforms, licensed by Microsoft from AT&T Corporation in the late 1970s.wikipedia
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Unix

UNIX operating systemAT&T UnixUnix-like
XENIX is a discontinued version of the UNIX operating system for various microcomputer platforms, licensed by Microsoft from AT&T Corporation in the late 1970s.
Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley (BSD), Microsoft (Xenix), IBM (AIX), and Sun Microsystems (Solaris).

Microsoft

Microsoft CorporationMicrosoft Corp.MS
XENIX is a discontinued version of the UNIX operating system for various microcomputer platforms, licensed by Microsoft from AT&T Corporation in the late 1970s.
Microsoft entered the operating system (OS) business in 1980 with its own version of Unix, called Xenix.

Version 7 Unix

Seventh Edition UnixVersion 7Unix v7
Microsoft, which expected that UNIX would be its operating system of the future when personal computers became powerful enough, purchased a license for Version 7 UNIX from AT&T in 1978, and announced on August 25, 1980, that it would make it available for the 16-bit microcomputer market.
The first Sun workstations (then based on the Motorola 68010) ran a V7 port by UniSoft; the first version of Xenix for the Intel 8086 was derived from V7 and Onyx Systems soon produced a Zilog Z8000 computer running V7.

Altos Computer Systems

AltosAltos 580Altos 68000
The first 8086 port was for the Altos Computer Systems' non-PC-compatible 8600-series computers (first customer ship date Q1 1982).
Altos Computer Systems was founded in 1977 by David G. Jackson and Roger William Vass Sr. It focused on small multi-user computers, starting with multi-user derivatives of CP/M, and later including Unix and Xenix-based machines.

Motorola 68000

68000M68000MC68000
The company stated that it intended to port the operating system to the Zilog Z8000 series, Digital LSI-11, Intel 8086 and 80286, Motorola 68000, and possibly "numerous other processors", and provide Microsoft's "full line of system software products", including BASIC and other languages.
The 68000 was used in Microsoft Xenix systems, as well as an early NetWare Unix-based Server.

Tandy Corporation

TandyTandy ComputersTandy Corp.
It did not sell XENIX directly to end users, but licensed the software to OEMs such as IBM, Intel, Management Systems Development, Tandy, Altos, SCO, and Siemens (SINIX) who then ported it to their own proprietary computer architectures.
That year, Tandy was the leading Unix vendor by volume, selling almost 40,000 units of the 68000-based, multiuser Tandy Model 16 with Xenix, and began selling all computers using the Tandy brand because, an executive admitted, "we were told by customers that the Radio Shack name was a problem in the office".

PDP-11

LSI-11PDP-11/70DEC PDP-11
The company stated that it intended to port the operating system to the Zilog Z8000 series, Digital LSI-11, Intel 8086 and 80286, Motorola 68000, and possibly "numerous other processors", and provide Microsoft's "full line of system software products", including BASIC and other languages. In 1981, Microsoft said the first version of XENIX was "very close to the original UNIX version 7 source" on the PDP-11, and later versions were to incorporate its own fixes and improvements.
In the early years, in particular, Microsoft's Xenix was ported to systems like the TRS-80 Model 16 (with up to 1 MB of memory) in 1983, and to the Apple Lisa, with up to 2 MB of installed RAM, in 1984.

SINIX

Reliant UNIXReliantUNIX
It did not sell XENIX directly to end users, but licensed the software to OEMs such as IBM, Intel, Management Systems Development, Tandy, Altos, SCO, and Siemens (SINIX) who then ported it to their own proprietary computer architectures.
The original SINIX was a modified version of Xenix and ran on Intel 80186 processors.

Multiplan

Microsoft Multiplan
The Multiplan spreadsheet was released for it.
Multiplan was released first for computers running CP/M; it was developed using a Microsoft proprietary p-code C compiler as part of a portability strategy that facilitated ports to systems such as MS-DOS, Xenix, Commodore 64 and 128, Texas Instruments TI-99/4A (on four 6K GROMs and a single 8K ROM), Radio Shack TRS-80 Model II, TRS-80 Model 4, TRS-80 Model 100 (on ROM), Apple II, and Burroughs B-20 series.

MS-DOS

DOSMS-DOS 5.0MS-DOS 6.0
Microsoft referred to its own MS-DOS as its "single-user, single-tasking operating system", and advised customers that wanted multiuser or multitasking support to buy XENIX.
Microsoft omitted multi-user support from MS-DOS because Microsoft's Unix-based operating system, Xenix, was fully multi-user.

Vaporware

vapourwareannouncing nonexistent productsannouncing products that never appeared
The decision was not immediately transparent, which led to the term vaporware.
"Vaporware" was coined by a Microsoft engineer in 1982 to describe the company's Xenix operating system and first appeared in print in a newsletter by entrepreneur Esther Dyson in 1983.

OS/2

OS/2 WarpIBM OS/2OS/2 Warp 4
It agreed with IBM to develop OS/2, and the XENIX team (together with the best MS-DOS developers) was assigned to that project.
Because of this heritage, OS/2 shares similarities with Unix, Xenix, and Windows NT.

Santa Cruz Operation

SCOThe Santa Cruz OperationSCO Forum
The Santa Cruz Operation (SCO) later acquired exclusive rights to the software, and eventually replaced it with SCO UNIX (now known as SCO OpenServer).
Santa Cruz Operation (SCO) was a software company based in Santa Cruz, California which was best known for selling three Unix variants for Intel x86 processors: Xenix, SCO UNIX (later known as SCO OpenServer), and UnixWare.

Protected mode

protected-mode16-bit protected mode286 protected mode
The later 286 version of XENIX leveraged the integrated MMU present on this chip, by running in 286 protected mode.
The initial protected mode, released with the 286, was not widely used; for example, it was used by Microsoft Xenix (around 1984), Coherent and Minix.

IBM System 9000

There was also a port for IBM System 9000.
All members had the IBM CSOS real-time operating system (OS) stored on read-only memory; and the System 9002 could also run the multi-user Microsoft Xenix OS, which was suitable for business use and supported up to four users.

UNIX System V

System VSVR4System V Release 4
It was followed by a System V.2 codebase in XENIX 5.0 (a.k.a. XENIX System V).
SCO XENIX also used SVR2 as its basis.

Zilog Z8000

Z8000Zilog Z8001Zilog Z8002
The company stated that it intended to port the operating system to the Zilog Z8000 series, Digital LSI-11, Intel 8086 and 80286, Motorola 68000, and possibly "numerous other processors", and provide Microsoft's "full line of system software products", including BASIC and other languages.
There was a Z8000 version of the Xenix Operating System

TRS-80 Model II

TRS-80 Model 16Model 16Model II
Tandy more than doubled the XENIX installed base when it made TRS-XENIX the default operating system for its TRS-80 Model 16 68000-based computer in early 1983, and was the largest UNIX vendor in 1984.
The Model 16 can run either TRSDOS-16 or TRS-Xenix, a variant of Xenix, Microsoft's version of UNIX.

OpenServer

SCO UNIXSCO OpenServerSCO
The Santa Cruz Operation (SCO) later acquired exclusive rights to the software, and eventually replaced it with SCO UNIX (now known as SCO OpenServer).
SCO UNIX was the successor to the Santa Cruz Operation's variant of Microsoft Xenix, derived from UNIX System V Release 3.2 with an infusion of Xenix device drivers and utilities.

Intel 80286

80286286Intel 286
The company stated that it intended to port the operating system to the Zilog Z8000 series, Digital LSI-11, Intel 8086 and 80286, Motorola 68000, and possibly "numerous other processors", and provide Microsoft's "full line of system software products", including BASIC and other languages.
Other operating systems that used the protected mode of the 286 were Microsoft Xenix (around 1984), Coherent, and Minix.

Apple Lisa

LisaLisa OSApple Lisa 2
In 1984, a port to the 68000-based Apple Lisa 2 was jointly developed by SCO and Microsoft and it was the first shrink-wrapped binary product sold by SCO.
The company Santa Cruz Operation, (SCO), offered Microsoft XENIX (version 3), a UNIX-like command-line interface operating system, for the Lisa 2 — and the Multiplan spreadsheet (version 2.1) for that.

UNIX System III

System IIIAT&T System III UNIXUNIX 3.2
While XENIX 2.0 was still based on Version 7 UNIX, version 3.0 was upgraded to a UNIX System III code base, A 1984 Intel manual for XENIX 286 noted that the XENIX kernel had about 10,000 lines at this time.
Third-party variants of System III include (early versions of) HP-UX, IRIX, IS/3 and PC/IX, PC-UX, PNX, SINIX, Venix and Xenix.

IBM Personal Computer/AT

IBM PC/ATIBM ATIBM PC AT
For example, the Sperry PC/IT, an IBM PC AT clone, was advertised as capable of supporting eight simultaneous dumb terminal users under this version.

Bochs

Many guest operating systems can be run using the emulator including DOS, several versions of Microsoft Windows, BSDs, Linux, Xenix and Rhapsody (precursor of Mac OS X).

SunOS

Sun OSSunits operating system
In the meantime, AT&T and Sun Microsystems completed the merge of XENIX, BSD, SunOS and System V.3 into System V Release 4.
In 1987, AT&T Corporation and Sun announced that they were collaborating on a project to merge the most popular Unix flavors on the market at that time: BSD (including many of the features then unique to SunOS), System V, and Xenix.