1.1. The MARC 21 formats are standards for the representation and communication of bibliographic and related information in machine-readable form.
1.2. A MARC record involves three elements: the record structure, the content designation, and the data content of the record.
1.2.1. The structure of MARC records is an implementation of national and international standards, e.g., Information Interchange Format (ANSI Z39.2) and Format for Information Exchange (ISO 2709).
1.2.2. Content designation, the codes and conventions established to identify explicitly and characterize further the data elements within a record and to support the manipulation of those data, is defined in the MARC 21 formats.
1.2.3. The content of most data elements is defined by standards outside the formats, e.g., Anglo-American Cataloguing Rules, Library of Congress Subject Headings, National Library of Medicine Classification. The content of other data elements, e.g., coded data section 9 below), is defined in the MARC 21 formats.