First Publicly Released Operating System by Company

Microsoft announced Xenix on 25/08/1980, marking the company’s first publicly released operating system and its initial entry into the Unix ecosystem. The system was based on Version 7 Unix, which Microsoft licensed from AT&T in 1979, and was intended to run on emerging 16-bit microprocessors rather than the 8-bit microcomputers common at the time. The announcement described Xenix as a portable Unix-based operating system designed for multiuser and multitasking capabilities on microcomputer platforms. Unlike later Microsoft operating systems, Xenix was not sold directly to consumers. Instead, Microsoft licensed the software to hardware manufacturers, including Intel, Tandy, Altos, and others, who adapted and bundled it with their own systems. This OEM-focused distribution model allowed vendors to port Xenix to multiple processor architectures such as Intel 8086 and Zilog Z8000. During the early 1980s, this approach helped Xenix spread across various microcomputer platforms, and it became widely deployed on multiuser business systems. Although Xenix represented Microsoft’s first operating system, the company’s strategic direction shifted soon afterward. In 1981, Microsoft entered a partnership with IBM to provide an operating system for the IBM Personal Computer, leading to the release of MS-DOS. As IBM PC compatibility became dominant in the personal computer market, Microsoft gradually moved its focus toward MS-DOS and later Windows-based platforms, while Xenix development was eventually transitioned to The Santa Cruz Operation (SCO) in the mid-1980s.