A type of operating system in which only user can work at time is called single-user operating system. Dos. Windows 8x are example of single- user operating system. Dos work on command it is most single-user operating system. Dos works on command it is most compatible with hardware Multi- operating systems / (multi tasking operating systems) A type of operating system in which more than one user can work at a time is called Multi- tasking operating system. Unix, Linux, Windows NT/ 2000 are examples of single- user operating systems.