KeyKOS

KeyKOS is a persistent, pure capability-based operating system for the IBM S/370 mainframe computers. It allows emulating the environments of VM, MVS, and Portable Operating System Interface (POSIX). It is a predecessor of the Extremely Reliable Operating System (EROS), and its successor operating systems, CapROS, and Coyotos. KeyKOS is a nanokernel-based operating system.^[1]

KeyKOS

Developer	Tymshare (Norm Hardy, Bill Frantz, Charlie Landau) McDonnell Douglas Key Logic
Written in	C
OS family	Capability-based
Working state	Discontinued
Initial release	1977; 48 years ago (1977)
Latest release	Final / 1988; 37 years ago (1988)
Marketing target	Research
Available in	English
Update method	Compile from source code
Platforms	S/370 mainframe
Kernel type	Microkernel
Default user interface	Command-line interface
Preceded by	GNOSIS
Succeeded by	Extremely Reliable Operating System (EROS), CapROS, Coyotos
Official website	cap-lore.com/CapTheory/KK

In the mid-1970s, development of KeyKOS began at Tymshare, Inc., under the name GNOSIS. In 1984, McDonnell Douglas (MD) bought Tymshare. A year later MD spun off Key Logic, which bought GNOSIS and renamed it KeyKOS.^[2]