(also USMARC, MARC 21), n. A data communications format that specifies a data structure for bibliographic description, authority, classification, community information, and holdings data.


An acronym for MAchine Readable Cataloging. MARC is a United States implementation of the Information Interchange Format (ANSI Z39.2). Other countries implemented that standard with minor variations. The variations included UKMARC, and CanMARC. Efforts to harmonize the variations to create a single standard are reflected by the use of the name MARC 21. See


MARC 21, 1998 The Library of Congress and the National Library of Canada are pleased to announce that the harmonized USMARC and CAN/MARC formats will be published in a single edition in early 1999 under a new name: MARC 21. The name both points to the future as we move into the 21st century and suggests the international character of the format, which is appropriate and important given its expanding worldwide use. ΒΆ MARC 21 is not a new format. From 1994-1997 the USMARC and CAN/MARC user communities worked to eliminate all remaining differences in their two already-similar formats. Compatibility had been a feature of the development processes for both formats for many years. In 1997 and early 1998, updates to the formats were issued that made the format specifications identical. MARC 21, a continuation of both USMARC and CAN/MARC, publishes the formats in one edition under a new name.