Abstract: The invention relates to an emulator system which allows a disk drive to transparently emulate a tape drive. The system converts sequential format tape records into block format disk records and visa-versa. Identification and conversion information for each of the data records are stored in directory located on the outermost sectors of the disk. Within each directory are a plurality of entries each containing four fields: TAPE RECORD NUMBER (TRN); DISK START ADDRESS (DSA); WORD COUNT (WC); and FLAG. These fields contain all of the necessary information required to map a tape formatted data record to a disk and thereafter retrieve the data record from the disk and convert it back to tape format.