Operating systems can be categorized by technology, ownership, licensing, working state, usage, and by many other characteristics. In practice, many of these groupings may overlap.
- Domain/OS One of the first network-based systems. Ran on Apollo/Domain hardware. Later bought by Hewlett-Packard.
- vikek OS
For Apple II
For Apple III
- SOS (Sophisticated Operating System)
For Apple Lisa
- Lisa OS
For Apple Newton
Classic Mac OS
- System Software 1
- System Software 2
- System Software 3
- System Software 4
- System Software 5
- System 6
- System 7 (codenamed "Big Bang")
- Mac OS 8
- Mac OS 9
Unix-like operating systems
- For Macintosh Computers
- For 68k CPUs
- For PowerPC CPUs
- For PowerPC and Intel CPUs
- For iPhone/iPod Touch/iPad
- Blue Eyed OS
- COS (Chippewa Operating System)
- RDOS Real-time Disk Operating System, with variants: RTOS and DOS (not related to IBM PC DOS).
- AOS for 16-bit Data General Eclipse computers and AOS/VS for 32-bit (MV series) Eclipses, MP/AOS for microNOVA-based computers
- CTOS Z-80 based, Cassette Tape Operating System for early desktop systems. Capable of up to 8 simultaneous users. Replaced by DataPoint DOS.
- DOS Intel 808x/80x86-based, Disk Operating Systems for desktop systems. Capable of up to 32 users per node. Supported a sophisticated network of nodes that were often purpose-built. The name DOS was used in these products login screens before it was popularized by IBM, Microsoft and others.
Digital Research Inc
- Control Program/Monitor (CP/M)
- DR-DOS (Digital Research's [later Novell, Caldera, ...] DOS variant, based on CP/M descendants)
- ITS (for the PDP-6 and PDP-10)
- Multi-Programming Executive (from HP)
- TOPS-10 (for the PDP-10)
- WAITS (for the PDP-6 and PDP-10)
- TENEX (from BBN, for the PDP-10)
- TOPS-20 (for the PDP-10)
- RSTS/E (multi-user time-sharing OS for PDP-11s)
- RSX-11 (multiuser, multitasking OS for PDP-11s)
- RT-11 (single user OS for PDP-11)
- VMS (originally by DEC, now by HP) for the VAX mini-computer range, Alpha and Intel Itanium 2; later renamed OpenVMS)
- Domain/OS (originally Aegis, from Apollo Computer who were bought by HP)
- RTE HP's Real Time Executive (ran on the HP 1000)
- TSB HP's Time Share Basic (yes, it was an operating system, ran on the HP 2000 series)
- Digital UNIX (derived from OSF/1, became HP's Tru64 UNIX)
- NonStop Kernel (Originally from Tandem Computers for their line of fault-tolerant platforms; originally called Guardian). It supports concurrent execution of:
- OSS (POSIX-compliant Open System Services)
- OSE Flexible, small footprint, high-performance RTOS for control processors
- OSEck Small footprint, scalable, high-performance RTOS for DSPs
- OSE ɛ Small footprint, scalable, high-performance RTOS for microcontrollers
- UTX-32, Unix based OS
- INTEGRITY Reliable Operating system
- INTEGRITY-178B A DO-178B certified version of INTEGRITY.
- µ-velOSity A lightweight microkernel.
- HP Real-Time Environment; ran on HP1000 series computers.
- HP Multi-Programming Executive; (MPE, MPE/XL, and MPE/iX) runs on HP 3000 and HP e3000 mini-computers.
- HP-UX; runs on HP9000 and Itanium servers - from small to mainframe-class computers.
- iRMX; real-time operating system originally created to support the Intel 8080 and 8086 processor families in embedded applications.
- ISIS-II; "Intel Systems Implementation Supervisor" was THE environment for development of software within the Intel microprocessor family in the early 1980'ies on their Intellec Microcomputer Development System and clones. ISIS-II worked with 8 inch floppy disks and had an editor, cross-assemblers, a linker, an object locator, debugger, compilers for PLM (PL/I for microprocessors of the 8080/86 family), a BASIC interpreter, etc. and allowed file management through a console.
- OS/360 and successors on IBM mainframes
- OS/360 (First official OS targeted for the System/360 architecture, saw customer installations of the following variations:)
- OS/VS (The official port of OS/360 targeted for the System/370 virtual memory architecture. "OS/370" is not correct name. Customer installations in the following variations:)
- SVS (Single Virtual Storage (both VS1 & VS2 began as SVS systems))
- OS/VS1 (Operating System/Virtual Storage 1, Virtual-memory version of OS/MFT)
- OS/VS2 (Operating System/Virtual Storage 2, Virtual-memory version of OS/MVT)
- OS/VS2 R2 (called Multiple Virtual Storage, MVS, eliminated any need for VS1)
- MVS/SP (MVS System Product)
- MVS/XA (MVS/SP V2. MVS supported eXtended Architecture, 31bit addressing)
- MVS/ESA (MVS supported Enterprise System Architecture, horizontal addressing extensions: data only address spaces called Dataspaces)
- OS/390 (Upgrade from MVS, with an additional Unix-like environment.)
- z/OS (OS/390 supported z/Architecture, 64bit addressing.)
- DOS/360 and successors on IBM mainframes
- BOS/360 (Early interim version of DOS/360, briefly available at a few Alpha & Beta System 360 sites)
- TOS/360 (Similar to BOS above and more fleeting, able to boot and run from 2x00 series tape drives)
- DOS/360 (Disk Operating System (DOS). First commonly available OS for System/360 due to problems in the OS/360 Project. Multi-programming system with up to 3 partitions.)
- DOS/360/RJE (DOS/360 with a control program extension that provided for the monitoring of remote job entry hardware (card reader & printer) connected by dedicated phone lines.)
- DOS/VS (First DOS offered on System/370 systems, provided virtual storage.)
- DOS/VSE (upgrade of DOS/VS. Still had fixed size processing partitions, but up to 14 partitions.)
- VSE/SP (renamed from DOS/VSE.)
- VSE/ESA (DOS/VSE extended virtual memory support to 32 bit addresses (Extended System Architecture)).
- z/VSE (Latest version of the four decades old DOS lineage. Now supports 64 bit addresses, multiprocessing, multiprogramming, SNA, TCP/IP, and some virtual machine features in support of Linux workloads. (All DOS ref. IBM website))
- CP/CMS and successors on IBM mainframes (Control Program / Cambridge Monitor System, virtual machine operating system, VM line)
- CP-40/CMS (for System/360 Model 40)
- CP-67/CMS (for System/360 Model 67)
- VM/370 Virtual Machine / Conversational Monitor System, VM (operating system) for System/370 with virtual memory.
- VM/XA VM (operating system) eXtended Architecture for System/370 with extended virtual memory.
- VM/ESA Virtual Machine /Extended System Architecture, added 32 bit addressing to VM series.
- z/VM z/Architecture version of the VM OS (64 bit addressing).
- TPF Line on IBM mainframes (real-time operating system, largely used by airlines)
- Unix-like on IBM mainframes
- Others on IBM mainframes
- IBSYS (tape based operating system for IBM 7090 and IBM 7094)
- CTSS (The Compatible Time-Sharing System developed at MIT's Computation Center)
- RTOS/360 (Real Time Operating System, run on 5 NASA custom System/360/75s. A mash up by the Federal Systems Division of the MFT system management, PCP basic kernel and file system, with MVT task management and FSD custom real time kernel extensions and error management. The pinnacle of OS/360 developmentTemplate:Cite.)
- MTS (Michigan Terminal System for IBM System/360)
- TSS/360 (Time Sharing System for IBM System/360)
- MUSIC/SP (developed by McGill University for IBM System/370)
- IJMON (A bootable serial I/O monitor for loading programs for IBM 1400 and IBM 1800.)
- IBM 8100
- IBM System/3
- DMS (Disk Management System)
- IBM System/88
- AS/400, iSeries, System i, Power Systems i Edition
- UNIX on IBM POWER
- IBM PC and successors on x86 architecture
- PC DOS / IBM DOS
- PC DOS 1.x, 2.x, 3.x (developed jointly with Microsoft)
- IBM DOS 4.x, 5.0 (developed jointly with Microsoft)
- PC DOS 6.x, 7, 2000
- PC DOS / IBM DOS
- J and MultiJob for the System 4 series mainframes
- GEORGE 2/3/4 GEneral ORGanisational Environment, used by ICL 1900 series mainframes
- Executive, used on the 290x range of minicomputers
- TME, used on the ME29 minicomputer
- ICL VME, including early variants VME/B VME/K, appearing on the ICL 2900 Series and Series 39 mainframes
LynuxWorks (originally Lynx Real-time Systems)
- MicroC/OS-II (Small pre-emptive priority based multi-tasking kernel)
- Xenix (licensed version of Unix; licensed to SCO in 1987)
- MSX-DOS (developed by MS Japan for the MSX 8-bit computer)
- MS-DOS (developed jointly with IBM, versions 1.0–6.22)
- Windows 9x
- OS/2 (developed jointly with IBM)
- Windows NT
- Windows NT 3.1 (OS/2 3.0 - Windows 3.1)
- Windows NT 3.5 (Windows 3.5)
- Windows NT 3.51 (Windows 3.51)
- Windows NT 4.0 (Windows 4)
- Windows 2000 (Windows NT 5.0 - Windows 5)
- Windows XP (Windows NT 5.1 - Windows 5.1) (codename: Whistler)
- Windows Server 2003 (Windows NT 5.2 - Windows 5.2) (codename: Whistler Server)
- Windows Fundamentals for Legacy PCs
- Windows Vista (Windows NT 6.0 - Windows 6) (codename: Longhorn)
- Windows Home Server
- Windows Server 2008 (Windows NT 6.0 - Windows 6) (codename: Longhorn Server)
- Windows 7 (Windows 6.1 - previously codenamed Blackcomb, then Vienna)
- Windows Preinstallation Environment (WinPE)
- Windows CE (OS for handhelds, embedded devices, and real-time applications that is similar to other versions of Windows)
- Singularity - A research operating system written mostly in managed code (C#)
- Midori - A managed code operating system
- MontaVista Linux
- MontaVista Professional Edition
- MontaVista Carrier Grade Edition
- MontaVista Mobilinux
- TMX - Transaction Management eXecutive
- NetWare network operating system providing high-performance network services. Has been superseded by Open Enterprise Server line, which can be based on NetWare or Linux to provide the same set of services.
- Open Enterprise Server, the successor to NetWare.
- OpenSUSE, SUSE operating system (formerly SuSe and s.u.s.e)
- RTXC Quadros RTOS proprietary C-based RTOS used in embedded systems
- BEST - Business Executive System for Timesharing
- TSOS, first OS supporting virtual addressing of the main storage and support for both timeshare and batch interface
- Unison RTOS Ultra Tiny Embedded Linux Compatible RTOS
- DSPnano RTOS Ultra Tiny Embedded Linux Compatible RTOS
- Unison/Reliant V3 pSOS derivative RTOS
- Xenix, Unix System III based distribution for the Intel 8086/8088 architecture
- SCO Unix, SCO UNIX System V/386 was the first volume commercial product licensed by AT&T to use the UNIX System trademark (1989). Derived from AT&T System V Release 3.2 with an infusion of Xenix device drivers and utilities plus most of the SVR4 features
- SCO OpenServer 5, AT&T UNIX System V Release 3 based
- SCO OpenServer 6, SVR5 (UnixWare 7) based kernel with SCO OpenServer 5 application and binary compatibility, system administration, and user environments
- Scos 1
- Scos 1.2
- Scos 1.5
- Scos 2.0
- Scos 2.5
- Scos 3
- Scos 4
- Scos 5
- Scos 6 (Latest Stable Version)
SDS (Scientific Data Systems)
- CP Control Program. SDS later acquired by Xerox, then Honeywell.
- Real Time Monitor (RTM)
- PikeOS is a certified real time operating system for safety and security critical embedded systems
- Fusion RTOS highly prolific, license free Real-time operating system.
- DSPOS was the original project which would become the royalty free Fusion RTOS.
UNIVAC (later Unisys)
- 2200T Wang BASIC based system for the multi-user, 2200T systems. Products included a system called Personal Computer before the term was made more popular with IBM products.
- 2200VP/MVP Wang BASIC based system for the higher performance, 2200VP/MVP multi-user systems. Contained sophisticated micro-code programming for high performance operation.
- WPS Wang Word Processing System. Micro-code based system. Very clever and productive system developed by Harold Kaplow while at Wang. Eventually phased out by the PC and Word Perfect.
- OIS Wang Office Information System. Successor to the WPS. Combined the WPS and VP/MVP systems. Harold Kaplow was its principal architect. Eventually phased out by the 2200VS.
- 2200VS IBM assembler instruction set microcode emulation. Supported the Wang 2200VS high-performance, multi-user systems. Designed to be a COBOL developers dream machine. Included some of the OIS operating system code. Eventually phased out by the UNIX operating system.
Wind River Systems
- VxWorks Small footprint, scalable, high-performance RTO
- Symbolics Genera written in a systems dialect of the Lisp programming language called ZetaLisp and Symbolics Common Lisp. Genera was ported to a virtual machine for the DEC Alpha line of computers.
- Texas Instruments' Explorer Lisp machine workstations also had systems code written in Lisp Machine Lisp.
- The Xerox 1100 series of Lisp machines ran an operating system written in Interlisp that was also ported to virtual machine called "Medley."
- Lisp Machines, Inc. also known as LMI, also ran an operating system based on MIT's Lisp Machine Lisp.
- The Mesa programming language was used to implement the Pilot operating system, used in Xerox Star workstations.
- PERQ Operating System (POS) was written in PERQ Pascal.
Other proprietary non-Unix-like
- EOS; developed by ETA Systems for use in their ETA-10 line of supercomputers
- EMBOS; developed by Elxsi for use on their mini-supercomputers
- GCOS is a proprietary Operating System originally developed by General Electric
- PC-MOS/386; DOS-like, but multiuser/multitasking
- SINTRAN III; an operating system used with Norsk Data computers.
- TRS-DOS; A floppy-disk-oriented OS supplied by Tandy/Radio Shack for their Z80-based line of personal computers.
- NewDos/80; A third-party OS for Tandy's TRS-80 personal computers.
- TX990/TXDS, DX10 and DNOS; proprietary operating systems for TI-990 minicomputers
- MAI Basic Four; An OS implementing Business Basic from MAI Systems.
- Michigan Terminal System; Developed by a group of American universities for IBM 360 series mainframes
- MUSIC/SP; an operating system developed for the S/370, running normally under VM
- SkyOS; commercial desktop OS for PCs
- TSX-32; a 32-bit operating system for x86 platform.
- OS ES; an operating system for ES EVM
- Prolog-Dispatcher; used to control Soviet Buran space ship.
Other proprietary Unix-like and POSIX-compliant
- Aegis (Apollo Computer)
- Amiga Unix (Amiga ports of Unix System V release 3.2 with Amiga A2500UX and SVR4 with Amiga A3000UX. Started in 1989, last version was in 1992)
- Clix (Intergraph's System V implementation)
- Coherent (Unix-like OS from Mark Williams Co. for PC class computers)
- DC/OSx (DataCenter/OSx was an operating system for MIPS based systems developed by Pyramid Technology)
- DG/UX (Data General Corp)
- DNIX from DIAB
- DSPnano RTOS (POSIX nanokernel, DSP Optimized, Open Source)
- Idris workalike from Whitesmiths
- INTERACTIVE UNIX (a port of the UNIX System V operating system for Intel x86 by INTERACTIVE Systems Corporation)
- IRIX from SGI
- NeXTSTEP (developed by NeXT; a Unix-based OS based on the Mach microkernel)
- OS-9 Unix-like RTOS. (OS from Microware for Motorola 6809 based microcomputers)
- OS9/68K Unix-like RTOS. (OS from Microware for Motorola 680x0 based microcomputers; based on OS-9)
- OS-9000 Unix-like RTOS. (OS from Microware for Intel x86 based microcomputers; based on OS-9, written in C)
- OSF/1 (developed into a commercial offering by Digital Equipment Corporation)
- QNX (POSIX, microkernel OS; usually a real time embedded OS)
- Rhapsody (an early form of Mac OS X)
- RISC/os (a port by MIPS of 4.3BSD to the RISC MIPS architecture)
- SCO UNIX (from SCO, bought by Caldera who renamed themselves SCO Group)
- SINIX (a port by SNI of Unix to the RISC MIPS architecture)
- Solaris (Sun's System V-based replacement for SunOS)
- SunOS (BSD-based Unix system used on early Sun hardware)
- SUPER-UX (a port of System V Release 4.2MP with features adopted from BSD and Linux for NEC SX architecture supercomputers)
- System V (a release of AT&T Unix, 'SVR4' was the 4th minor release)
- System V/AT, 386 (The first version of AT&T System V UNIX on the IBM 286 and 386 PCs, ported and sold by Microport)
- Trusted Solaris (Solaris with kernel and other enhancements to support multilevel security)
- UniFLEX (Unix-like OS from TSC for DMA-capable, extended addresses, Motorola 6809 based computers; e.g. SWTPC, GIMIX, ...)
- Unicos (the version of Unix designed for Cray Supercomputers, mainly geared to vector calculations)
- Unison RTOS (Multicore RTOS with DSP Optimization)
Research Unix-like and other POSIX-compliant
- Minix (study OS developed by Andrew S. Tanenbaum in the Netherlands)
- Plan 9 (distributed OS developed at Bell Labs, based on original Unix design principles yet functionally different and going much further)
- Unix (OS developed at Bell Labs ca 1970 initially by Ken Thompson)
- Xinu, (Study OS developed by Douglas E. Comer in the USA)
Free/Open source Unix-like
- BSD (Berkeley Software Distribution, a variant of Unix for DEC VAX hardware)
- μnix (concept unix-like operating system for ATMEL microcontrollers)
- Linux (GNU Free/Open Source Operating System Software combined with the Linux kernel)
- OpenSolaris, contains original Unix (SVR4) code
- AuroraUX, fork of OpenSolaris
- SSS-PC, developed at Tokyo University
- Syllable Desktop
- FMI/OS, successor of VSTa
- TUNIS (University of Toronto)
- Amoeba (research OS by Andrew S. Tanenbaum)
- Cambridge CAP computer operating system demonstrated the use of security capabilities, both in hardware and software, also a useful fileserver. Written in ALGOL 68C.
- House Haskell User's Operating System and Environment, research OS written in Haskell and C.
- ILIOS Research OS designed for routing
- EROS microkernel, capability-based
- L4 Second generation microkernel
- Mach (from OS kernel research at Carnegie Mellon University; see NeXTSTEP)
- MONADS, capability-based OS designed to support the MONADS hardware projects
- SPEEDOS (Secure Persistent Execution Environment for Distributed Object Systems) builds on MONADS ideas
- Nemesis Cambridge University research OS - detailed quality of service abilities.
- Spring (research OS from Sun Microsystems)
- V from Stanford, early 1980s 
- FreeNOS, a microkernel educational operating system
Free/Open source non-Unix-like
- FullPliant (programming language-based)
- FreeDOS (open source DOS variant)
- FreeVMS (open source VMS variant)
- Haiku (open source inspired by BeOS, under development)
- Kinetic (written in Haskell)
- MonaOS (written in C++)
- ReactOS (Windows NT-compatible OS, in early development since 2001)
- osFree (open source OS/2 implementation)
- OZONE (object-oriented)
- MustiOS (32-bits operating system)
Disk Operating Systems
- 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.)
- FreeDOS (open source DOS variant)
- ProDOS (operating system for the Apple II series computers)
- PTS-DOS (DOS variant by Russian company Phystechsoft)
- RDOS by Leif Ekblad (not to be confused with Data General Corporation's "Real-time Disk Operating System" for Data General Nova and Data General Eclipse minicomputers).
- TurboDOS (Software 2000, Inc.) for Z80 and Intel 8086 processor-based systems
- Multi-tasking user interfaces and environments for DOS
- Cambridge Ring
- CSIRONET by (CSIRO)
- CTOS (Convergent Technologies, later acquired by Unisys)
- Data ONTAP by NetApp
- SAN-OS by Cisco (now NX-OS)
- Enterprise OS by McDATA
- ExtremeWare by Extreme Networks
- ExtremeXOS by Extreme Networks
- Fabric OS by Brocade
- JUNOS (Juniper Networks)
- NetWare (networking OS by Novell)
- NOS (developed by CDC for use in their Cyber line of supercomputers)
- Novell Open Enterprise Server (Open Source networking OS by Novell. Can incorporate either SUSE Linux or Novell NetWare as its kernel).
- Plan 9 (distributed OS developed at Bell Labs, based on Unix design principles but not functionally identical)
- TurboDOS (Software 2000, Inc.)
- XPATH OS by Brocade
Web operating systems
Generic/commodity and other
- Bluebottle also known as AOS (a concurrent and active object update to the Oberon operating system)
- BS1000 by Siemens AG
- BS2000 by Siemens AG, now BS2000/OSD from Fujitsu-Siemens Computers (formerly Siemens Nixdorf Informationssysteme)
- BS3000 by Siemens AG (functionally similar to OS-IV and MSP from Fujitsu)
- FLEX9 (by TSC for Motorola 6809 based machines; successor to FLEX, which was for Motorola 6800 CPUs)
- FutureOS (for Amstrad/Schneider CPC6128 and CPCPlus machines)
- GEM (windowing GUI for CP/M, DOS, and Atari TOS)
- GEOS (popular windowing GUI for PC, Commodore, Apple computers)
- JNode JNode.org's OS written 99% in Java (native compiled), provides own JVM and JIT compiler. Based on GNU Classpath
- JX Java operating system that focuses on a flexible and robust operating system architecture developed as an open source system by the University of Erlangen.
- KERNAL (default OS on Commodore 64)
- MERLIN for the Corvus Concept
- MorphOS (Amiga compatible)
- MSP by Fujitsu (successor to OS-IV), now MSP/EX, also known as Extended System Architecture (EXA), for 31-bit mode
- nSystem by Luis Mateu at DCC, Universidad de Chile
- NetWare (networking OS by Novell)
- Oberon (operating system) (developed at ETH-Zürich by Niklaus Wirth et al.) for the Ceres and Chameleon workstation projects.
- OSD/XC by Fujitsu-Siemens (BS2000 ported to an emulation on a Sun SPARC platform)
- OS-IV by Fujitsu (based on early versions of IBM's MVS)
- Pick (often licensed and renamed)
- PRIMOS by Prime Computer (sometimes spelled PR1MOS and PR1ME)
- Sinclair QDOS (multitasking for the Sinclair QL computer)
- SSB-DOS (by TSC for Smoke Signal Broadcasting; a variant of FLEX in most respects)
- SymbOS (GUI based multitasking operating system for Z80 computers)
- Symobi (GUI based modern micro-kernel OS for x86, ARM and PowerPC processors, developed by Miray Software; used and developed further at Technical University of Munich)
- TraOS, kin to Darwin? Seems active late 2009
- TripOS, 1978
- TurboDOS (Software 2000, Inc.)
- UCSD p-System (portable complete programming environment/operating system/virtual machine developed by a long running student project at the Univ Calif/San Diego; directed by Prof Ken Bowles; written in Pascal)
- UMIX, made for the ICFP Programming Contest 2006.
- ScaraOS, a 32 bit mutiboot OS kernel for IA32
- VOS by Stratus Technologies with strong influence from Multics
- VOS by Hitachi for its IBM-compatible mainframes, based on IBM's MVS
- VM2000 by Siemens AG
- VisiOn (first GUI for early PC machines; not commercially successful)
- VPS/VM (IBM based, main operating system at Boston University for over 10 years.)
- aceos under GPL
- Miraculix Russian OS, under unknown license.
For Elektronika BK
- ROM embedded
- OS BK-11 (RT-11 version)
- OS/A WASP
- AROS (AROS Research Operating System, formerly known as Amiga Research Operating System)
- AtheOS (branched to become Syllable Desktop)
- DexOS, (Games console OS, for x86, written in FASM)
- DSPnano RTOS FREE
- EROS (Extremely Reliable Operating System)
- FAMOS (Foremost Advanced Memory Operating System)
- HelenOS, based on a preemptible microkernel design
- LoseThos, the stated goal is "programming as entertainment" - oriented toward video games
- MenuetOS (extremely compact OS with GUI, written entirely in FASM assembly language)
- Möbius (an open-source operating system for the IA-32 platform (Intel i386 and compatibles) )
- Unison RTOS FREE
Personal digital assistants (PDAs)
- iPhone OS (a subset of Mac OS X)
- Inferno (distributed OS originally from Bell Labs)
- Palm OS from Palm, Inc; now spun off as PalmSource
- Symbian OS
- Windows CE, from Microsoft
- Embedded Linux
- MS-DOS on Poqet PC
- Newton OS on Apple Newton Messagepad
- VT-OS for the Vtech Helio
- Magic Cap
- Plan 9 from Bell Labs
Digital media players
- Robotic Operating System
- Dave's Robotic Operating System 
- BlackBerry OS
- Embedded Linux
- iPhone OS (a subset of Mac OS X)
- JavaFX Mobile
- Palm OS
- Symbian OS
- Symbian platform (successor to Symbian OS)
- Windows Mobile (recently changed to Windows Phone)
- AlliedWare by Allied Telesis (aka Allied Telesyn)
- AirOS by Ubiquiti Networks
- CatOS by Cisco Systems
- Cisco IOS (originally Internetwork Operating System) by Cisco Systems
- CyROS by Cyclades Corporation
- DD-WRT by NewMedia-NET
- Inferno (distributed OS originally from Bell Labs)
- IOS-XR by Cisco Systems
- IronWare by Foundry Networks
- JunOS by Juniper Networks
- RouterOS by Mikrotik
- ROX by Ruggedcom
- ScreenOS by Juniper Networks, originally from Netscreen
- Timos by Alcatel-Lucent
- Unison Operating System by RoweBots
- FTOS by Force10 Networks
- RTOS by Force10 Networks
- .NET Micro Framework
- polyBSD (embedded NetBSD)
- Windows Embedded
- Windows CE
- Windows Embedded Standard
- Windows Embedded Enterprise
- Windows Embedded POSReady
- KeyKOS nanokernel
- MONADS, designed to support the MONADS hardware projects.
- SPEEDOS builds on MONADS ideas
- V from Stanford, early 1980s