i am a looking for a good research on UX and UI of the modern Operating systems and how the OS is being evolved in the UX department and how is it going to be in the future.
Article User-Experience of Tablet Operating System: An Experimental ...
I'll second Peter's comments and add to it. The User eXperience is all about how a user can do the tasks that they need to do efficiently and effectively. This can be done through a GUI (Graphical User Interface) that is application specific (think MS Word) or more "system wide" (think Windows / Cocoa / KDE / Gnome) - or often through a CLI (Command Line Interface)
With the "system wide" GUIs - they really only provide a consistent framework and set of widgets for the developer. Adding a user is an command (or application in Peter's diagram), it can be done via a GUI (giving a certain UX) or from the command line. The information required for both will be the same, and the underlying interactions with the OS will be identical.
Operating System has two major roles mainly i.e. as a hardware resource manager and as a virtualization of Harware resources. I would disagree that OS has noting to do with the UX and UI. Altough UX and UI may be not counted as OS's main functions, but it is important part of our everyday means of interaction with computers.