total no of operating systems exist on earth {part:-3}

Operating systems (573)

Oaesis
Oasis
Oberon
Objex
Odin
Omega 4
OnCore
On Time RTOS-32
Opal
OpenBeOS
OpenBSD
OpenDarwin
OpenRavenscar
OpenServer
OpenVision
OpenVMS
OppcOS
OS-2
OS-9
OS-C
OS/2
OS/2 Warp
OS/9
OS/360
OS/390
OS/400
OS/ES
OS/M
OS4
osCAN
OSE
OSF/1
Osx
OZONE
PAKOS
Palm OS
PAPL
Paramecium
ParixOS
Paros
PaulOS
P BASIC
PC-BSD
PC-DOS
PC/M-System
PDOS
PEACE
Pebble
Pegasos
PETROS
Phantom OS
Phos
PIOS
PizziOS
Plan 9
Plex86
PM_SZ_OS
PocketPC 2003
PowerMAX
PowerOS
PowerSX
PowerUX
ProDOS
Prologue
Proolix
ProOSEK
PSOS
pSOSystem
PSU
PTS DOS
PublicOS
PURE
QDOS
QNX
Quadros
RadiOS
RBASIC
RCOSjava
RDOS
ReactOS
REAL-32
Realogy Real Time Architekt
REBOL-IOS
ReWin
REX-80/86
REXX/OS
RHODOS
RISC OS
RMOS
RMS 68k
Roadrunner
ROME
Rome
RSTS/E
RSX-11
RT-11
RTEL
RTEMS
RT Mach NTT
rtmk
RTMX
RTOS-32
RTOS-UH
RTS-80
RTX
RTXDOS
RxDOS