Amoeba – research OS by Andrew S. Tanenbaum Barrelfish Croquet EROS – microkernel, capability-based CapROS – microkernel EROS successor Harmony – realtime, multitasking, multiprocessing message-passing system developed at the National Research Council of Canada. HelenOS – research and experimental operating system House – Haskell User's Operating System and Environment, research OS written in Haskell and C ILIOS – Research OS designed for routing L4 – second generation microkernel Mach – from OS kernel research at Carnegie Mellon University; see NeXTSTEP Nemesis – Cambridge University research OS – detailed quality of service abilities Singularity – experimental OS from Microsoft Research written in managed code to be highly dependable Spring – research OS from Sun Microsystems THE multiprogramming system – by Dijkstra in 1968, at the Eindhoven University of Technology in the Netherlands, introduced the first form of software-based memory segmentation, freeing programmers from being forced to use actual physical locations Thoth – realtime, multiprocess message-passing system developed at the University of Waterloo. V – from Stanford, early 1980s Verve – OS designed by Microsoft Research to be verified end-to-end for type safety and memory safety Xinu – Study OS developed by Douglas E. Comer in the United States Disk operating systems (DOS) 86-DOS (developed at Seattle Computer Products by Tim Paterson for the new Intel 808x CPUs; licensed to Microsoft, became PC DOS/MS-DOS. Also known by its working title QDOS.) PC DOS (IBM's DOS variant, developed jointly with Microsoft, versions 1.0–7.0, 2000, 7.10) MS-DOS (Microsoft's DOS variant for OEM, developed jointly with IBM, versions 1.x–6.22 Microsoft's now abandoned DOS variant) Concurrent CP/M-86 3.1 (BDOS 3.1) with PC-MODE (Digital Research's successor of CP/M-86 and MP/M-86) Concurrent DOS 3.1-4.1 (BDOS 3.1-4.1) Concurrent PC DOS 3.2 (BDOS 3.2) (Concurrent DOS variant for IBM compatible PCs) DOS Plus 1.1, 1.2 (BDOS 4.1), 2.1 (BDOS 5.0) (single-user, multi-tasking system derived from Concurrent DOS 4.1-5.0) Concurrent DOS 8-16 (dual-processor variant of Concurrent DOS for 8086 and 8080 CPUs) Concurrent DOS 286 1.x FlexOS 1.00-2.34 (derivative of Concurrent DOS 286) FlexOS 186 (variant of FlexOS for terminals) FlexOS 286 (variant of FlexOS for hosts) Siemens S5-DOS/MT (industrial control system based on FlexOS) IBM 4680 OS (POS operating system based on FlexOS) IBM 4690 OS (POS operating system based on FlexOS) Toshiba 4690 OS (POS operating system based on IBM 4690 OS and FlexOS) FlexOS 386 (later variant of FlexOS for hosts) IBM 4690 OS (POS operating system based