 The implementation of DCL for RT-11 increased its compatibility with the other DEC operating systems.Although each operating system had commands and options which were unique to that operating system, there were a number of commands and command options which were common.DEC also sold RSX-11, a multiuser, multitasking operating system with realtime features, and RSTS/E (originally named RSTS-11) a multiuser time-sharing system, but RT-11 remained the operating system of choice for data acquisition systems where real time response was required.