Penny's OS (S 16)

 
or PAIPIX or PAKOS
or paldo GNU/Linux or Palm OS
or PAPL or ParallelKnoppix
or Paramecium or Pardus
or ParixOS or Paros
or Parsix or Parslinux
or PaulOS or PC-BSD
or PC-DOS or PC/IX
or PCLinuxOS or PCLOS
or PC-MOS/386 or PC/NOS
or PC/OS or PCP
or PCUNIX or PCVMS
or PDOS or PDP-6 Monitor
or PDP-10 or PEACE
or Peanut Linux or Pebble
or PelicanHPC or Penguin Sleuth
or Pentoo or Perpos
or Pequelin or PERQ-OS
or Peter Operating System or PetrOS
or pfSense or Phaeronix
or Phantomix or Phantom OS
or Phar Lap ETS or Phat Linux
or PHLAK or Phoenix
or Phoenix-RTOS or phos
or Pick or PicoBSD
or PICOS18 or Pie Box
or PikeOS or Pilot
or Pingo or Pingwinek
or Pioneer or PIOS
or PIRAT or Pitt Time Sharing
or PixelOS or PixoOS
or PizziOS or Plamo
or Plan B or Plan 9
or PLD Linux or PLoP Linux
or Plurix or PM_SZ_OS
or PNX or Pocket Linux
or POK or polyBSD
or polyFORTH or PortixOS
or Portos or PORTX
or POS or P/OS
or Poseidon Linux or POSYS
or PowerMAX OS or PowerOS
or PowerSX or PowerUX
or Pozix Linux or pQui Linux
or Presto or Prex
or PRIMOS or ProDOS
or Progeny Componentized Linux or Progeny Debian
or Progex or PROLOGUE
or Proolix or Pro-OS
or ProOSEK or ProTech
or PRO/TSX-PLUS or pSOS
or pSOSystem or PS2 Linux
or psubuntu or PSX
or PsygNAT or p-System
or PTOS or PTS-DOS
or PTSS or P!tux
or PublicOS or PUD
or Puma or Puppy Linux
or pureDarwin or puredyne
or PureOS or PureOSlight
or PWB/Unix or PXROS