Used in the field of library science. consist of the MARC formats, which are standards for the representation and communication of bibliographic and related information in machine-readable form, and related documentation. It defines a bibliographic data format that was developed by Henriette Avram at the Library of Congress beginning in the 1960s. 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 record structure of MARC is an implementation of ISO 2709, also known as ANSI/NISO Z39.2.[1] MARC records are composed of three elements: the record structure, the content designation, and the data content of the record. The record structure implements national and international standards (e.g., Z39.2, ISO2709). The content designation is "the codes and conventions established to identify explicitly and characterize ... data elements within a record"[1] and support their manipulation. The content of data elements in MARC records is defined by standards outside the formats such as AACR2, L.C. Subject Headings, and MeSH.