SkyOS was a prototype commercial, proprietary

Proprietary software

Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...

, graphical desktop operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 written for the x86 computer architecture

Computer architecture

In computer science and engineering, computer architecture is the practical art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals and the formal modelling of those systems....

. As of January 30, 2009 development has halted and no plans to resume its development have been announced.
SkyOS is the culmination of over ten years of research and development by Robert Szeleney and volunteers.

A young man at the university, Szeleney and several friends began the "Sky Operating System" as an experiment in OS design.