Overview
ISO/IEC 9660:2023 specifies the standardized volume and file structure of CD-ROM media to enable reliable information interchange between different information-processing systems. The standard defines how data is arranged and described on a CD‑ROM, the attributes of volumes and files, and the functional requirements for systems that create or read compliant discs. It targets compatibility and predictable interoperability for CD‑ROM based distribution and archival use.
Key technical topics and requirements
- Volume and descriptor attributes - formal descriptors recorded on the medium that identify and describe each volume and its properties.
- Volume set relationships - rules that govern how multiple volumes in a set relate and interoperate.
- File placement and attributes - how files and associated metadata are stored and referenced on the data area.
- Record structures for I/O streams - definitions for fixed- and variable-length records and measured data units to support applications that require record-organized data streams.
- Medium interchange levels - specification of three nested levels of medium interchange to define different portability/compatibility profiles.
- Implementation levels - two nested levels of implementation to guide feature support for producers and readers.
- Conformance requirements - criteria both for CD‑ROM media and for information processing systems that originate or consume compliant discs.
- Directory and path table organization - hierarchical directory rules, path table structure and ordering to support efficient directory traversal.
- Descriptor field encoding - rules for numeric fields (8/16/32-bit and byte orders), character sets and file/directory identifiers, and recording conventions for descriptors (including boot and terminator records).
(These topics are reflected in the standard’s clauses on volume structure, directory hierarchy, path tables, record structure, and descriptor encoding.)
Practical applications
- Creating interoperable CD‑ROMs for software distribution, multimedia content, documentation sets, and archival delivery.
- Implementing CD‑ROM authoring tools, file system drivers, and emulator software that must read/write standardized discs.
- Digital archives and libraries that require long-term preservation with predictable on‑disc metadata and directory structures.
- Embedded and legacy systems that rely on CD‑ROM as a transport medium.
- Forensic and data-recovery workflows that need a formal model of how data and descriptors are recorded.
Who should use this standard
- Software developers and OS vendors implementing CD‑ROM file system support
- CD/DVD mastering and authoring tool creators
- Archivists and digital preservation specialists
- Hardware and firmware engineers for optical media readers
- QA and compliance teams verifying interchangeability and conformance
Related considerations
ISO/IEC 9660 is the baseline specification for CD‑ROM file systems; implementers often consider it alongside vendor or extension profiles and other optical-media standards when targeting specific compatibility or feature sets.
Keywords: ISO/IEC 9660, CD‑ROM, volume and file structure, file system, volume descriptor, directory hierarchy, path table, record structure, conformance, interchange.