In 1977, the IFLA (International Federation of Library Associations) published the first edition of UNIMARC: Universal MARC Format, followed by a second edition in 1980 and a UNIMARC Handbook in 1983. UNIMARC (Universal Machine Readable Cataloging) is a common bibliographic format for library catalogs, as a solution to the 20 existing national MARC (Machine Readable Cataloging) formats, which meant lack of compatibility and extensive editing when bibliographical records were exchanged. With UNIMARC, catalogers would be able to process records created in any MARC format. Records in one MARC format would first be converted into UNIMARC, and then be converted into another MARC format.
At the time, the future of online catalogs was linked to the harmonization of the MARC format. Set up in the early 1970s, MARC is an acronym for Machine Readable Catalogue. This acronym is rather misleading as MARC is neither a kind of catalog nor a method of cataloguing. According to UNIMARC: An Introduction, a document of the Universal Bibliographic Control and International MARC Core Programme, MARC is "a short and convenient term for assigning labels to each part of a catalogue record so that it can be handled by computers. While the MARC format was primarily designed to serve the needs of libraries, the concept has since been embraced by the wider information community as a convenient way of storing and exchanging bibliographic data."
After MARC came MARC II. MARC II established rules to be followed consistently over the years. The MARC communication format intended to be "hospitable to all kinds of library materials; sufficiently flexible for a variety of applications in addition to catalogue production; and usable in a range of automated systems."
Over the years, however, despite cooperation efforts, several versions of MARC emerged, e.g. UKMARC, INTERMARC and USMARC, whose paths diverged because of different national cataloguing practices and requirements. We had an extended family of more than 20 MARC formats. Differences in data content meant some extensive editing was needed before records could be exchanged.
One solution to incompatible data was to create an international MARC format - called UNIMARC - which would accept records created in any MARC format. Records in one MARC format would first be converted into UNIMARC, and then be converted into another MARC format, so that each national bibliographic agency would need to write only two programs - one to convert into UNIMARC and one to convert from UNIMARC - instead of having to write twenty programs for the conversion of each MARC format (e.g. INTERMARC to UKMARC, USMARC to UKMARC etc.).