This International Standard specifies requirements for the file structure and the labelling of flexible disk cartridges for the interchange of information between users of different information processing systems. This International Standard specifies a) recorded labels to identify files, file sections, and volumes of flexible disk cartridges; b) basic characteristics of the blocks containing the records constituting the file; c) the file structure. This International Standard specifies three nested levels of interchange so that a) at the first level, called BASIC INTERCHANGE (BI), it is possible to interchange data by using a minimum set of the facilities provided; b) at the second level, called EXTENDED INTERCHANGE LEVEL 1 (E1), it is possible to interchange data using the minimum set together with blocks having a length greater than that of the physical records and with blocked fixedlength records; c) at the third level, called EXTENDED INTERCHANGE LEVEL 2 (E2), it is possible to interchange data using the facilities of levels Bl and E1 together with variable-length records and segmented records. Annex A describes examples but does not form part of this standard. Annex B gives disk parameter values derived from flexible disk data interchange standards, but does not form part of this standard.