DeveloperTymshare (Norm Hardy, Bill Frantz, Charlie Landau)
McDonnell Douglas
Key Logic
Written inC
OS familyCapability-based
Working stateDiscontinued
Initial release1977; 47 years ago (1977)
Latest releaseFinal / 1988; 36 years ago (1988)
Marketing targetResearch
Available inEnglish
Update methodCompile from source code
PlatformsS/370 mainframe
Kernel typeMicrokernel
user interface
Command-line interface
Preceded byGNOSIS
Succeeded byExtremely Reliable Operating System (EROS), CapROS, Coyotos

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]

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]


  1. ^ The KeyKOS Nanokernel Architecture Archived 2011-06-21 at the Wayback Machine
  2. ^ "Roots of KeyKOS".