WAndroid Cupcake
WAndroid Donut
WAndroid Gingerbread
WAndroid Honeycomb
WAsteroidOS
WCatamount (operating system)
WCNK operating system
WEMILE
WExit (command)
WFiwix
WIBMDOS.COM
WIPhone OS 1
WMX4J
WPocket PC 2002
WPTS-DOS
WSyllable Desktop
WSystem Manager (HP LX)
WType (Unix)
WWindows Mobile 2003
WWizard of OS
WZephyr (operating system)