Penny's OS (S 18)

 
                             or RadiOS
or Raidiator or RAMON
or RAX or RAYS LX
or RBASIC or RBM
or RC-4000 or RCOSjava
or RDOS or ReactOS
or Real.Dos or REALITY
or REAL/IX or REAL NG
or REAL/32 or Real-Time Mach
or Real VMX or REBOL-IOS
or Recovery is Possible or Red Dice
or Red Flag Linux or RedHawk Linux
or Redmond Linux Personal or RedOS
or Redphish or Reduced Core Monitor
or redWall Firewall or REGULUS
or ReHMuDi or RelaxBSD
or Reliant UNIX or Renix
or Repairlix or REPOS
or Rhapsody or RHODOS
or RIG or RIO/CP
or RIPLinux or RISC iX
or RISC OS or RM/COS
or RMOS or RMS
or RMS09 or RMS68K
or RMX or RMX-80
or RMX-86 or Roadrunner
or RockBox or ROCK Linux
or Rocks Cluster or RoFReeSBIE
or ROM-DOS or Rome
or ROOT GNu/Linux or ROS
or Roscoe or ROSLIMS
or ROX Desktop or rPath
or rPath Linux or RPS
or RR4 Linux or RSEXEC
or RSTS/E or RSTS-11
or RSX-11 or RTAI
or RTA-OSEK or RTE
or RTEL or RT-11
or RTEMS or RT/EMT
or RTEX or RTLinux
or RTM or RT-Mach
or RTM8 or rtmk
or RTMOS or RTMX O/S
or RTOS or RToS-80
or RTOS-32 or RTOS-UH
or RTR or RT-Thread
or RTTS or RTU
or RTUX or RTX
or RTX/Tiny or RTXC Quadros
or RTXDOS or Rubix
or Ruby or Russian Fedora
or Rx or Rxart
or RxDOS or RYMOS