MS-DOS V2.11 and CP/M- AP400 Mainboard 008131-001 /80 V2.1 operating systems combined in one package. AP400 Mainboard 008131-001-A3 Rainbow's MS-DOS V2.11, an enhanced version of the Microsoft operating system, includes a AP400 Mainboard 008131-001 utility that reads CP/M diskettes so that users can transfer data stored in CP/M format to MS-DOS format. AP400 Mainboard 008131-001-A3 CP/M-86/80 V2.1, a combination of Digital Research 16-bit CP/M-86 and 8-bit CP/M-80 with additional Utilities. AP400 Mainboard 008131-001-A3