DOS Plus (erroneously also known as DOS+) is an operating system written by Digital Research, first released in 1985. It can be seen as an intermediate step between CP/M-86 and DR-DOS. It is able to run programs written for either CP/M-86 or MS-DOS 2.11, and can read and write the floppy formats used by both these systems. Up to four CP/M-86 programs can be multitasked, but only one DOS program can be run at a time.