What are different operating systems available on the market?

there are basically 6 OS

Windows

Linux

Linux

dos

mactonish

Apple

symbian

that i know

even though there lots of version available

VMS

Ms Dos

Ms- Windows series

unix

Linux series

Mac Os

IBM OS/2 Warp

AmigaOS[30]

GEM

Symbian

there are much more we don't know abt