IFLA Working Group on Content Designators recommended in d973 a SUPERMARC, which was based on ISBD. This was later called MARC International Format (MIF) from which the UNIMARC was developed. The final format was published in 1977. The group recognised the lack of standardisation in cataloguing as the major obstacle to a standard MARC format. Language differences and variations in subject control systems and headings for author and title files were supplementary reasons preventing the inter-tangibility of records. The functional differences between a national bibliography, and a national library were the main reasons compelling each library to develop its own format.
The IFLA Working Group after investigating the difference in content designators and exploring the ways to accommodate these differences in the best way recommended a standard for international interchange of bibliographic data. Thus, the development of UNIMARC was undertaken. It is a communication format, which would necessitate the writing and maintaining of only two conversion programs - one from the national format to the UNIMARC and the other form the UNIMARC to the national format. It was decided that each country could have its national format but, it should be the responsibility of the national bibliographic agency in a country to translate the records from the national format to the UNIMARC for purposes of interchange. ISBD was accepted as the basis of the descriptive data elements within this format. A second edition of UNIMARC was published by IFLA International Office for UBC with a handbook with the intention of guiding the users in its application, Content designators for a variety of materials got standardised in this. Books, periodicals, maps, globes, music, scores, sound recordings, motion pictures, video-recordings, pictures, drawings, sculptures, artifacts, computer files and other related forms of materials have been covered by this standard. Non-Roman script is also accommodated.
UNIMARC uses a special block structure in the place of areas. Data in national formats may be carried in different position but UNIMARC can identify these data functionally and establish clearly designated areas for them as the blocks.