Overview
ISO 4341:1978 - Information processing - Magnetic tape cassette and cartridge labelling and file structure for information interchange - defines a standardized method to structure, label and delimit files recorded on magnetic tape cassettes and cartridges for reliable information interchange. The standard specifies three levels of sophistication for labelling and file structure: the basic system, the compact system, and the extended system. Although developed with 3.81 mm cassettes in mind, ISO 4341:1978 is applicable to higher-capacity cassettes and cartridges.
Key topics and technical requirements
- Three system levels
- Basic system: Uses hardware-defined separators (tape marks) only to indicate start/end of volume, file separators, intermediate track starts/ends and end-of-data. Support for the basic system is mandatory for interchangeability.
- Compact system: Introduces magnetically recorded labels - 32-character blocks - that can be recorded with equipment using only numeric characters. Labels provide metadata such as volume identifier, file identifier, file section number, creation date, retention period and block count.
- Extended system: Builds on ISO 1001 labelling and adds more comprehensive label fields for sophisticated environments.
- Labels and format
- Labels are distinct blocks (not part of files) placed at beginnings/ends of volumes, tracks or files.
- Typical label types include File Header (HDR), End of Track (ETR), End of Volume (EOV) and End of File (EOF). HDR contains fields like creation date, retention period and block count.
- Labels are 32 characters long and use the ISO 646 7‑bit coded character set; the compact system allows “n” (numeric) and selected “a” (alphanumeric) characters in certain fields.
- Tape marks and tape structure
- Tape marks (single and double) are used to separate labels from file data and to signal structural boundaries. Two consecutive tape marks usually indicate end of data unless framing an empty file section.
- Operational rules
- All volumes in a file set must be recorded at the same density.
- By-pass and check-point records are not standardized for interchange and are not permitted on interchange cassettes.
- Retention period plus creation date defines expiration; expired files may be overwritten.
Applications and users
ISO 4341:1978 is relevant for:
- Data archivists and records managers implementing long-term tape interchange and retention policies.
- Tape drive and media manufacturers and firmware developers who implement label recognition, tape mark handling and multi-volume file structures.
- System integrators and IT teams migrating legacy tape datasets between platforms.
- Organizations exchanging bulk data via magnetic tape where consistent file delimitation, labeling and expiration control are required.
Related standards
- ISO 646 - 7‑bit coded character set
- ISO 1001 - Magnetic tape labelling and file structure (extended labelling)
- ISO 3275 - Implementation of 7‑bit coded set
- ISO 3407 - 3.81 mm magnetic tape cassette for information interchange
Keywords: ISO 4341:1978, magnetic tape cassette, cartridge, file structure, labelling, information interchange, tape marks, HDR label, compact system, extended system.