MARC is an acronym for MAchine-Readable Cataloging.  The five MARC 21 communication formats, MARC 21 Format for Bibliographic Data, MARC 21 Format for Authority Data, MARC 21 Format for Holdings Data, MARC 21 Format for Classification Data, and MARC 21 Format for Community Information, are widely used standards for the representation and exchange of bibliographic, authority, holdings, classification, and community information data in machine-readable form.

Each MARC format provides detailed field descriptions and guidelines for applying the defined content designation and identifies conventions to be used to insure input consistency.

See also:

Holdings Data Format:  Introduction