Machine-Readable Cataloging (MARC)
An international standard digital format for the description of bibliographic items developed by the Library of Congress during the 1960s to facilitate the creation and dissemination of computerized cataloging from library to library within the same country and between countries. By 1971, the MARC format had become the national standard for dissemination of bibliographic data and by 1973, an international standard.
There are several versions of MARC in use in the world, the most predominant being MARC 21, created in 1999 as a result of the harmonization of U.S. and Canadian MARC formats, and UNIMARC, widely used in Europe. The MARC 21 family of standards now includes formats for authority records, holdings records, classification schedules, and community information, in addition to formats for the bibliographic record.
Widespread use of the MARC standard has helped libraries acquire predictable and reliable cataloging data, make use of commercially available library automation systems, share bibliographic resources, avoid duplication of effort, and ensure that bibliographic data will be compatible when one automation system is replaced by another.
The MARC record has three components:
Record structure - an implementation of national and international standards, such as the Information Interchange Format ANSI Z39.2 and Format for Information Exchange ISO 2709
Content designation - codes and conventions that explicitly identify and characterize the data elements within a record to facilitate the manipulation of data, defined in the MARC 21 Format for Bibliographic Data and other MARC 21 formats maintained by the Library of Congress
Data Content - defined by external standards such as AACR2, Library of Congress Subject Headings (LCSH), etc.
The MARC record is divided into fields, each containing one or more related elements of bibliographic description. A field is identified by a three-digit tag designating the nature of its content. Tags are organized as follows in hundreds, indicating a group of tags, with XX in the range of 00-99:
0XX fields - Control information, numbers, codes
1XX fields - Main entry
2XX fields - Titles, edition, imprint
3XX fields - Physical description, etc.
4XX fields - Series statements (as shown in item)
5XX fields - Notes
6XX fields - Subject added entries
7XX fields - Added entries other than subject or series
8XX fields - Series added entries (other authoritative forms)