1K
| AdaOS | DTOS | LegOS | PaulOS | Syllable |
| ADMIRAL | DVIX | leJOS | P BASIC | Symbian OS |
| Adrenaline | DYNIX Unix (Sequent) | Linux | PC-BSD | SymbOS |
| aerolitheOS | ECL-3211 | Lisa OS | PC-DOS | Symobi |
| Aimos | eComStation | LTSS | PC/M-System | Symphony OS |
| AIOS | eCos | LynxOS | PDOS | Synapse |
| AIX | EduOS | Möbius | PEACE | System 6 (Mac OS) |
| AIX/370 | EGOS | Mach | Pebble | System 7 (Mac OS) |
| AIX/ESA | ekkoBSD | Mac OS 8 | Pegasos | System V Release |
| Allegro | Elate | Mac OS 9 | PETROS | TABOS |
| AllianceOS | ELKS | Mac OS X | Phantom OS | Tabos |
| Alto OS | Elysium | MANOS | Phos | TalOS |
| Amiga OS | EOS | MaRTE OS | PIOS | TAOS |
| Amoeba | EP/IX | Maruti | PizziOS | TENEX |
| Amstrad | EPOC | Masix | Plan 9 | THE |
| AMX RTOS | ERaMS | Maverick OS | Plex86 | Thix |
| AngelOS | ERIKA | MBOS | PM_SZ_OS | ThreadX |
| Antarctica | EROS | MCP (Master Control Program) | PocketPC 2003 | ThrillOS |
| AOS/VS | ESER | MDOS | PowerMAX | TI-99 4A |
| Aperios | ESIX | MenuetOS | PowerOS | TinyOS |
| Apollo Domain/OS | ESKO | Merlin | PowerSX | TIS APL |
| ApolloOS | Eumel | Micriµm | PowerUX | TNIX |
| Apostle | EuNIX | MICRODOS | ProDOS | TOPS-10 |
| Archimedes OS | Exopc | MicroVMS | Prologue | TOPS-20 |
| AROS | ExOS | MikeOS | Proolix | TriangleOS |
| ARTOS | Express | Minima | ProOSEK | Tripos |
| Asbestos | Famos | Minix | PSOS | TRON |
| Athena | FDOS | Minux | pSOSystem | TRS-DOS |
| AtheOS | Fiasco | Miranda | PSU | Tru64 UNIX |
| AtomsNet | Flamethrower | Miray µnOS | PTS DOS | TSX-32 |
| Atomthreads | FlashOS | MITE 80/IOS | PublicOS | TUD:OS |
| AuroraOS | FlexOS | MK++ | PURE | TUNES |
| B-Free | FLP-80 DOS | ML | QDOS | TurboDOS |
| Bada | Flux | ModulOS | QNX | UberOS |
| BAL | Flux-Fluke-Flask | Monitor | Quadros | UCSD-p |
| Banyan VINES | FMS | MOPS | RadiOS | UDOS |
| Basic Executive System | Forth | MorphOS | RBASIC | Ultrix |
| BeIA | FreeBSD | MOS | RCOSjava | UMDS |
| BeOS | FreeDOS | MOSIX | RDOS | UMN |
| Beowulf | FreeDOWS | MPE/iX | ReactOS | UNI/OS |
| BKY | FreeVMS | MPE OS | REAL-32 | Unicos |
| BlueEyedOS | Frenzy | MRT1700 | Realogy Real Time Architekt | UNICOS/lc |
| BOS | FullPliant | MS-DOS | REBOL-IOS | Uni FLEX |
| BOS1810 | FunatixOS | MSOS | RMOS | Unisys U5000 |
| BoxOS | FxOS | MT809 | RMS 68k | Unix System |
| BPMK | GazOS | Multics | Roadrunner | UnixWare |
| bpmk | GCOS | Mungi | Rome | Unununium |
| BRiX | GECOS | MUTOS | ROME | USIX |
| BS600 | GeekOS | muVinix | RSTS/E | UTS |
| BS2000 | Gemini Nucleus | MVS | RSX-11 | UXP/V |
| BSDi | Genera | NachOS | RT-11 | V2 OS |
| BugOS | GEORGE | NCR Unix | RTEL | Vapour |
| Calmira | GEOS | NEC DOS | RTEMS | VERSAdos |
| CCP (Computer Control Program) | GM OS | NECUX | RT Mach NTT | Visopsys |
| CDOS | GNU Hurd | Nemesis | rtmk | Visual Network OS |
| Cefarix | GNUstep | NeOS | RTMX | VM/ESA |
| C Executive | Go | NetBSD | RTOS-32 | VM/VSE |
| Chaos | Goah | Netware | RTOS-UH | VME |
| Chimera | Gould OS | NewDeal | RTS-80 | VMS |
| Chippewa OS | Grasshopper | NEWDOS | RTX | VRTX/8002 |
| Choices | GUIDE | NewOS | RTXDOS | VRTX/OS |
| Chorus | Haïku | Nexus | RxDOS | VSE |
| Cinder OS | HA-MSP | Nimbus | S.Ha.R.K | VSOS |
| Cisco IOS | Hactar | Node OS | Sanos | VSTa |
| Clicker32 | Harmony | NOS | SCO OpenServer | VTOS |
| CMW+ (SCO) | Helios | NOS/BE | SCOPE | VxWorks |
| COBRA | HES | NOS/VE | ScorchOS | WEGA |
| Coherent | Hive | Nova | ScottsNewOS | WildMagnolia |
| CONSENSYS | HOPE | Novell DOS | Scout | Windows 7 |
| ConvexOS | HP-87 OS | NS/GDOS | SCP | Windows 8 |
| Cos | HP-UX | NSK | SCP (System Control Program) | Windows 95 |
| Cosy | HT-11 | NTDIOS | SCP-IBE | Windows 98 |
| Counterpoise | Hurd | Nucleus | Self-R | Windows 98 SE |
| CP/K | Hurricane | Oaesis | SeOS | Windows 2000 |
| CP/M | HydrixOS | Oasis | Sequent | Windows Automotive |
| CP/NET | i5/OS | Oberon | SEVMS VAX | Windows CE |
| CP/Z | IBM PC-DOS | Objex | Shark | Windows ME |
| CPF (Control Program Facility) | IBSYS | Odin | SharpOS | Windows NT |
| Cromix | Icaros Desktop | Omega 4 | ShawnOS | Windows Server 2003 |
| Cronus | Iridium OS | OnCore | SIBO | Windows Server 2003 R2 |
| CSOC | IRIX | On Time RTOS-32 | Sinclair | Windows Server 2008 |
| CTOS | iRMX | Opal | Sinix | Windows Server 2008 R2 |
| CTSS | IRTS | OpenBeOS | SINTRAN III | Windows Vista |
| CX/SX | ISC (Interactive) | OpenBSD | SkyOS | Windows XP |
| Cyber (CDC) | ISIS | OpenDarwin | Slikware | WinMac |
| Cygnus | ISSL | OpenRavenscar | sMultiTA | WIZRD |
| DAC | ITRON | OpenServer | SOBS | x-kernel |
| Darwin | ITS | OpenVision | Solaris | XAOS |
| Data General | JAMB | OpenVMS | Solar_OS | Xenix |
| DC/OSx | JavaOS | OppcOS | Solbourne UNIX | Xinu |
| DCP | Jbed | OS-2 | SOS | xMach |
| Degenerate OS | JeniOS | OS-9 | SP6800 | XOS |
| Delitalk | Jeo-OS | OS-C | Spice | XTS |
| Deming OS | Jibbed | OS/2 | Spice/MT | Yamit |
| DEMOS | JOS | OS/2 Warp | SPIN | Yaxic |
| DesktopBSD | JTMOS | OS/9 | Spinix | Yoctix |
| DESKWORK | JUNOS | OS/360 | SPOX | z-VM |
| DG/UX | JxOS | OS/390 | Spring | z/OS |
| DIGITAL UNIX | KAOS | OS/400 | Squeak | Z9001-OS |
| dingOS | Katix | OS/ES | SSP (System Support Program) | ZealOS |
| DK/DOS | Kea | OS/M | STAR-OS | Zeta |
| DLD | Kerberos | OS4 | STARCOS | Zeus Zilog |
| DNIX | KeyKOS | osCAN | Starplex II OS | zeVenOS |
| Domain OS | KOS | OSE | Sting | ZMOS |
| DOS | KRONOS | OSF/1 | StreamOS | ZotOS |
| DOS2 | KROS | Osx | Subsump | ZRTS 8000 |
| DOS 50 | KRUD | OZONE | SUMO | |
| Dosket | Kylin | PAKOS | SunMOS | |
| dr’ex | L4 | Palm OS | SunOS | |
| DR-DOS | L13Plus | PAPL | SunriseOS | |
| Drops | LainOS | Paramecium | SuperDOS | |
| Drywell OS | LAN Manager | ParixOS | SVM | |
| DS-OS | LDOS | Paros | SVR |
