QNX cant be a result of symbian since it is 20years older than symbian and completely different. http://en.wikipedia.org/wiki/QNX RTOS cant be a os since it is a definition. http://en.wikipedia.org/wiki/Real-time_operating_system Also linux, bsd and qnx has their roots in unix, which inturn has its roots in multics. http://en.wikipedia.org/wiki/Multics also, win 1,2 and finally 3 to 3.11 and windows for workgroups, are very different from winNT but also predates winNT. OS/2 should also be there since winNT=os/2 ver3.