<Tr> <Td> Old version, no longer supported: X11R4 </Td> <Td> 000000001989 - 12 - 22 - 0000 22 December 1989 </Td> <Td> XDMCP, twm brought in as standard window manager, application improvements, shape extension, new fonts . </Td> </Tr> <Tr> <Td> Old version, no longer supported: X11R5 </Td> <Td> 000000001991 - 09 - 05 - 0000 5 September 1991 </Td> <Td> X386 1.2, PEX, Xcms (color management), font server, X video extension . </Td> </Tr> <Tr> <Td> Old version, no longer supported: X11R6 </Td> <Td> 000000001994 - 05 - 16 - 0000 16 May 1994 </Td> <Td> ICCCM v2. 0; Inter-Client Exchange; X Session Management; X Synchronization extension; X Image extension; XTEST extension; X Input; X Big Requests; XC - MISC; XFree86 changes . </Td> </Tr> <Tr> <Td> Old version, no longer supported: X11R6. 1 </Td> <Td> 000000001996 - 03 - 14 - 0000 14 March 1996 </Td> <Td> X Double Buffer extension; X keyboard extension; X Record extension . </Td> </Tr>

Which type of user group provides backwards compatibility with windows xp