David RossDavid Ross 522 bronze badges 1 1 The SUB is really an artefact of CP/M, exactly where it had been utilized being an EOF marker (CP/M "duration" was blocks, not bytes). MSDOS was made to have the ability to examine CP/M files, & because it was very likely at some time that CP/M can be accustomed to browse the resuts from MSDOS, the ability