CP/M-86 was a version of the CP/M operating system that Digital Research (DR) made for the Intel 8086 and Intel 8088. The commands are those of CP/M-80. Executable files used the relocatable .CMD file format (the same filename extension .CMD is used by Microsoft Windows for unrelated batch files). Digital Research also produced a multi-user multitasking operating system compatible with CP/M-86, MP/M-86, which later evolved into Concurrent CP/M-86. When an emulator was added to provide PC DOS compatibility, the system was renamed to Concurrent DOS, which later became Multiuser DOS. The DOS Plus, FlexOS and DR DOS families of operating systems started as derivations of Concurrent DOS.