MARC Cataloging

MARC is an acronym for MAchine-Readable Cataloging. It is a communications standard for exchanging bibliographic, holdings, and other data between libraries. It defines a bibliographic data format that emerged from a United States Library of Congress led initiative that began in the 1970s. It provides the protocol by which computers exchange, use, and interpret bibliographic information. Its data elements make up the foundation of most library catalogs used today.
The MARC Standards Office is part of the Library of Congress.
The record structure of MARC is an implementation of ISO 2709, also known as ANSI/NISO Z39.2.
The future of the MARC formats is a matter of some debate in the worldwide library science community. On the one hand, the formats are quite complex and are based on outdated technology. On the other, there is no alternative bibliographic format with an equivalent degree of granularity.

Authority records -- MARC authority records provide information about individual names, subjects, and uniform titles. An authority record establishes an authorized form of each heading, with references as appropriate from other forms of the heading.

Bibliographic records -- MARC bibliographic records describe the intellectual and physical characteristics of bibliographic resources (books, sound recordings, video recordings, and so forth).

Holdings records -- MARC holdings records provide copy-specific information on a library resource (call number, shelf location, and so forth).