David RossDavid Ross 522 bronze badges 1 one The SUB is really an artefact of CP/M, the place it absolutely was applied as an EOF marker (CP/M "duration" was blocks, not bytes). MSDOS was developed in order to study CP/M information, & since it was probable at enough time that CP/M could be utilized to study the resuts from MSDOS, a chance to contr