The document specifies the file structure for data interchange on magnetic tape cassettes: a) this basic system, employing only hardware-defined separators to structure the files; b) the compact system, employing special data blocks with information content (labels), which are capable of being recorded using only numeric equipment; c) the extended system, employing the magnetic tape labelling system specifies in ISO 1001 together with new labels, to define a more comprehensive labelling system.#,,#