High Quality Content by WIKIPEDIA articles! Digital Tape Format is a magnetic tape data storage format developed by Sony. It uses a 1/2" wide tape, in a cassette with two reels, which is written and read with a helical scan process. The format is described by the ECMA 248 (adopted June 1998) and ISO/IEC 15731 standards. There are two sizes of tape cassettes, "S" and "L".