Xenix

Xenix. It was a version of the Unix operating system, licensed by Microsoft from AT&T Corporation in the late 1970s. Due to early licensing restrictions, Microsoft could not sell it directly under the Unix name, leading to the portmanteau branding. The system was subsequently sub-licensed to various original equipment manufacturers and software vendors, most notably The Santa Cruz Operation, which became its primary developer and distributor. Xenix played a crucial role in popularizing Unix-like environments on the proliferating Intel 8086, Zilog Z8000, and other 16-bit and 32-bit microprocessor platforms throughout the 1980s.

History and development

In 1979, Microsoft signed a licensing agreement with AT&T Corporation for Version 7 Unix, seeking to enter the multi-user operating system market. The initial port to the Zilog Z8000 platform was completed by 1980. Facing legal restrictions on the Unix trademark, the product was renamed. Early development involved adapting the system for the Intel 8086 architecture, with significant work done by a team that included future Sun Microsystems co-founder Andreas Bechtolsheim. As the complexities of supporting multiple hardware platforms grew, Microsoft turned to The Santa Cruz Operation in 1982 to assume primary development and support duties. This partnership allowed the system to evolve through several major releases, incorporating features from both BSD and System V as the Unix wars progressed. Development continued actively until the late 1980s, when strategic shifts at Microsoft toward OS/2 and the emerging collaboration with IBM on that project led to the eventual sale of all rights to The Santa Cruz Operation in 1987.

Technical features

Based initially on Version 7 Unix, the system integrated later elements from BSD 4.2 and System V. It supported a monolithic kernel and featured a command-line interface through the Bourne shell and later the Korn shell. Key technical advancements included the introduction of a merged virtual memory and file system architecture in later versions, enhancing performance on Intel 80386 systems. It offered robust support for TCP/IP networking, STREAMS, and the X Window System, making it a viable platform for technical workstations. The operating system was known for its portability across diverse central processing unit architectures, including the Motorola 68000 series and the Digital Equipment Corporation PDP-11. Its file system implemented standard Unix file system permissions and supported features like file locking critical for multi-user database applications such as those from Oracle Corporation and Informix.

Variants and ports

The system was ported to an exceptionally wide array of hardware due to its licensing model with original equipment manufacturers. Important early versions included those for the Altos Computer Systems 586 and the Intel System 86 board. A significant port to the Apple Lisa was developed, though never officially released. The most successful and enduring line began with the collaboration with The Santa Cruz Operation, leading to versions for the Intel 80286 and, most importantly, the Intel 80386. Tandy Corporation sold it pre-installed on their Tandy 6000 and Model 16 computers. Other notable ports were created for Siemens systems, the IBM PC/AT, and even the British Broadcasting Corporation BBC Micro via an auxiliary second processor. These variants often included proprietary hardware drivers and slight modifications to the kernel but maintained core application compatibility.

Market impact and legacy

It served as the dominant commercial Unix variant for microcomputers throughout much of the 1980s, outselling AT&T Corporation's own System V on these platforms. Its success demonstrated the viability of Unix in business environments on affordable hardware, paving the way for the client-server computing model. The operating system formed the direct foundation for The Santa Cruz Operation's subsequent product lines, including SCO OpenServer and SCO UnixWare, which became entrenched in point of sale and small business server markets. Furthermore, the experience gained by Microsoft in its development informed later projects, including aspects of XENIX's influence seen in early versions of OS/2 and even the Windows NT kernel architecture. While ultimately superseded by Linux and BSD derivatives in the Unix-on-Intel market, its role in transitioning the Unix philosophy from minicomputers to the burgeoning personal computer industry was historically pivotal.

Category:Unix variants Category:Microsoft operating systems Category:Discontinued operating systems Category:1980 software