What is the purpose of cataloging library materials?

Library collections house a wide variety of materials on many different topics and in many different formats. The challenge in making these things available for the use of library patrons is letting those patrons know what is in the library collection. This is the reason for having a library catalog, and for taking the time to correctly catalog library materials.

The library catalog might be compared to the index for a book.  The index provides the reader with a way to find information in the book without having to read every page.  The index tells the reader the page on which the information about a specific subject can be found.  The library catalog does the same thing.  It tells the library user exactly where materials meeting their specific needs can be found, with the call number of the book corresponding to the page number in an index.

The information contained in the cataloging record provides the many access points needed by the patron looking for information in the library. Traditionally, the library card catalog provided access by the author’s name, the title of an item, and the subject(s) covered in the item. Other points of access were additional authors, names of series, illustrators, and sometimes the titles of contents. 

Computer catalogs can, in theory, provide access to any part of the information contained in the record for an item in the library. The development of MARC (Machine Readable Cataloging) in the 1960’s made it possible to encode all areas of a cataloging record to be searchable. In MARC cataloging, each piece of information in a catalog record is given a numerical code, or field, and sometimes an alphabetical or numerical sub field. This coding makes it possible for a computer program to be written that looks for particular numbered fields when a particular type of search, such as a subject or title, is requested. Because all of the information in the cataloging record is encoded, searches could optionally be done by ISBN number, by series, by publisher, by date; or by any of the pieces of information stored in the cataloging record. MARC has set the standard for all computer catalogs used in libraries today, and if the records contained in the catalog comply with MARC requirements, the only controls on areas to be searched are the limits of the particular cataloging program.

When library materials are cataloged in a careful and complete manner, access is provided for the library patrons and staff to all sources of information on a particular topic, by a particular author, or in a particular format, that the library possesses. The better the access, the more use the collection receives, and the more satisfied the patron is in his or her search for information in the library.