A library catalog (or library catalogue) is a register of all bibliographic items found in a library or group of libraries, such as a network of libraries at several locations. A bibliographic item can be any information entity (e.g., books, computer files, graphics, realia, cartographic materials, etc.) that is considered library material (e.g., a single novel in an anthology), or a group of library materials (e.g., a trilogy), or linked from the catalog (e.g., a webpage) as far as it is relevant to the catalog and to the users (patrons) of the library.
The card catalog was a familiar sight to library users for generations, but it has been effectively replaced by the online public access catalog (OPAC). Some still refer to the online catalog as a "card catalog". Some libraries with OPAC access still have card catalogs on site, but these are now strictly a secondary resource and are seldom updated. Many of the libraries that have retained their physical card catalog post a sign advising the last year that the card catalog was updated. Some libraries have eliminated their card catalog in favour of the OPAC for the purpose of saving space for other use, such as additional shelving.
Charles Ammi Cutter made the first explicit statement regarding the objectives of a bibliographic system in his Rules for a Printed Dictionary Catalog in 1876. According to Cutter, those objectives were
1. to enable a person to find a book of which either (Identifying objective)
- the author
- the title
- the subject
- the category
2. to show what the library has (Collocating objective)
- by a given author
- on a given subject
- in a given kind of literature
3. to assist in the choice of a book (Evaluating objective)
- as to its edition (bibliographically)
- as to its character (literary or topical)
These objectives can still be recognized in more modern definitions formulated throughout the 20th century. 1960/61 Cutter's objectives were revised by Lubetzky and the Conference on Cataloging Principles (CCP) in Paris. The latest attempt to describe a library catalog's goals and functions was made in 1998 with Functional Requirements for Bibliographic Records (FRBR) which defines four user tasks: find, identify, select, and obtain.
A catalog also serves as an inventory or bookkeeping of what's in the library. If an item (a book) is not found in the catalog, the user doesn't have to search the shelves but can continue her search at another library. Library thieves, who may be staff or regular visitors of the library, risk to be discovered if a book is in the catalog but missing from the shelves. To avoid this, some library thieves have been careful to also steal the catalog card describing the book.
Catalog card 
|This section requires expansion. (March 2012)|
A catalog card is an individual record in a library catalog. In a physical catalog the record fills one small card, which is placed in order in the catalog drawer depending on the type of record. Here's an example of a catalog card, which would be filed alphabetically in the Author section:
Arif, Abdul Majid. Political structure in a changing Pakistani village / by Abdul Majid Arif and Basharat Hafeez Andaleeb. -- 2nd ed. -- Lahore : ABC Press, 1985. xvi, 367p. : ill. ; 22 cm. Includes index. ISBN 969-8612-02-8
Traditionally, there are the following types of catalog:
- Author catalog: a formal catalog, sorted alphabetically according to the authors' or editors' names of the entries.
- Title catalog: a formal catalog, sorted alphabetically according to the title of the entries.
- Dictionary catalog: a catalog in which all entries (author, title, subject, series) are interfiled in a single alphabetical order. This was the primary form of card catalog in North American libraries just prior to the introduction of the computer-based catalog.
- Keyword catalog: a subject catalog, sorted alphabetically according to some system of keywords.
- Mixed alphabetic catalog forms: sometimes, one finds a mixed author / title, or an author / title / keyword catalog.
- Systematic catalog: a subject catalog, sorted according to some systematic subdivision of subjects. Also called a Classified catalog.
- Shelf list catalog: a formal catalog with entries sorted in the same order as bibliographic items are shelved. This catalog may also serve as the primary inventory for the library.
Library catalogs originated as manuscript lists, arranged by format (folio, quarto, etc.) or in a rough alphabetical arrangement by author. Printed catalogs, sometimes called dictionary catalogs, began to be published in the early modern period and enabled scholars outside a library to gain an idea of its contents. Copies of these in the library itself would sometimes be interleaved with blank leaves on which additions could be recorded, or bound as guardbooks in which slips of paper were bound in for new entries. Slips could also be kept loose in cardboard or tin boxes, stored on shelves. The first card catalogs appeared in the late 19th century after the standardization of the 5 in. x 3 in. card for personal filing systems, enabling much more flexibility, and towards the end of the 20th century the Online public access catalog was developed (see below). These gradually became more common as some libraries progressively abandoned such other catalog formats as paper slips (either loose or in sheaf catalog form), and guardbooks. The beginning of the Library of Congress's catalog card service in 1911 led to the use of these cards in the majority of American libraries. An equivalent scheme in the United Kingdom was operated by the British National Bibliography from 1956 and was subscribed to by many public and other libraries.
- c. 245 BC: Callimachus is considered the first bibliographer and is the one that organized the library by authors and subjects. The Pinakes (Ancient Greek: Πίνακες "tables") was the first ever library catalogue. Variations on this system were used in libraries until the late 1800s when Melvil Dewey developed the Dewey Decimal Classification in 1876, which is still in use today.
- c. 800: Library catalogues are introduced in the House of Wisdom and other medieval Islamic libraries where books are organized into specific genres and categories.
- 1595: Nomenclator of Leiden University Library appears, the first printed catalog of an institutional library.
- 1674: Thomas Hyde's catalog for the Bodleian Library.
More about the early history of library catalogs has been collected in 1956 by Strout.
In a title catalog, one can distinguish two sort orders:
- In the grammatical sort order (used mainly in older catalogs), the most important word of the title is the first sort term. The importance of a word is measured by grammatical rules; for example, the first noun may be defined to be the most important word.
- In the mechanical sort order, the first word of the title is the first sort term. Most new catalogs use this scheme, but still include a trace of the grammatical sort order: they neglect an article (The, A, etc.) at the beginning of the title.
The grammatical sort order has the advantage that often, the most important word of the title is also a good keyword (question 3), and it is the word most users remember first when their memory is incomplete. However, it has the disadvantage that many elaborate grammatical rules are needed, so that only expert users may be able to search the catalog without help from a librarian.
In some catalogs, persons' names are standardized, i. e., the name of the person is always (cataloged and) sorted in a standard form, even if it appears differently in the library material. This standardization is achieved by a process called authority control. An advantage of the authority control is that it is easier to answer question 2 (which works of some author does the library have?). On the other hand, it may be more difficult to answer question 1 (does the library have some specific material?) if the material spells the author in a peculiar variant. For the cataloguer, it may incur (too) much work to check whether Smith, J. is Smith, John or Smith, Jack.
For some works, even the title can be standardized. The technical term for this is uniform title. For example, translations and re-editions are sometimes sorted under their original title. In many catalogs, parts of the Bible are sorted under the standard name of the book(s) they contain. The plays of William Shakespeare are another frequently cited example of the role played by a uniform title in the library catalog.
Many complications about alphabetic sorting of entries arise. Some examples:
- Some languages know sorting conventions that differ from the language of the catalog. For example, some Dutch catalogs sort IJ as Y. Should an English catalog follow this suit? And should a Dutch catalog sort non-Dutch words the same way?
- Some titles contain numbers, for example 2001: A Space Odyssey. Should they be sorted as numbers, or spelled out as Two thousand and one?
- de Balzac, Honoré or Balzac, Honoré de? Ortega y Gasset, José or Gasset, José Ortega y?
For a fuller discussion, see collation.
In a subject catalog, one has to decide on which classification system to use. The cataloguer will select appropriate subject headings for the bibliographic item and a unique classification number (sometimes known as a "call number") which is used not only for identification but also for the purposes of shelving, placing items with similar subjects near one another, which aids in browsing by library users, who are thus often able to take advantage of serendipity in their search process.
Online catalogs 
Online cataloging, through such systems as the Dynix software developed in 1983 and used widely through the late 1990s, has greatly enhanced the usability of catalogs, thanks to the rise of MARC standards (an acronym for MAchine Readable Cataloging) in the 1960s.
Rules governing the creation of MARC catalog records include not only formal cataloging rules such as AACR2 (Anglo-American Cataloguing Rules, Second Edition) but also rules specific to MARC, available from both the U.S. Library of Congress and the OCLC, the Online Computer Library Center global cooperative which builds and maintains WorldCat.
MARC was originally used to automate the creation of physical catalog cards, but its use evolved into direct access to the MARC computer files during the search process.
- The online catalog does not need to be sorted statically; the user can choose author, title, keyword, or systematic order dynamically.
- Most online catalogs allow searching for any word in a title or other field, increasing the ways to find a record.
- Many online catalogs allow links between several variants of an author's name.
- The elimination of paper cards has made the information more accessible to many people with disabilities, such as the visually impaired, wheelchair users, and those who suffer from mold allergies or other paper- or building-related problems.
See also 
- Dewey Decimal Classification
- International Standard Bibliographic Description
- Social cataloging applications
- Union catalog
- The curious tale of the stolen books, by Martin Vennard for BBC News Magazine, April 24, 2013.
- E.g. (1) Radcliffe, John Bibliotheca chethamensis: Bibliothecae publicae Mancuniensis ab Humfredo Chetham, armigero fundatae catalogus, exhibens libros in varias classas pro varietate argumenti distributos; [begun by John Radcliffe, continued by Thoams Jones]. 5 vols. Mancuni: Harrop, 1791-1863. (2) Wright, C. T. Hagberg & Purnell, C. J. Catalogue of the London Library, St. James's Square, London. 10 vols. London, 1913-55. Includes: Supplement: 1913-20. 1920. Supplement: 1920-28. 1929. Supplement: 1928-53. 1953 (in 2 vols). Subject index: (Vol. 1). 1909. Vol. 2: Additions, 1909-22. Vol. 3: Additions, 1923-38. 1938. Vol. 4: (Additions), 1938-53. 1955.
- Walford, A. J., ed. (1981) Walford's Concise Guide to Reference Material. London: Library Association; p. 6
- Simon Eliot, Jonathan Rose (2009). "A Companion to the History of the Book". John Wiley and Sons. p.90. ISBN 1-4051-9278-X
- Micheau, Francoise, "The Scientific Institutions in the Medieval Near East", pp. 988–991 in (Morelon & Rashed 1996, pp. 985–1007)
- The French Cataloging Code of 1791
- Strout, R.F. (1956), "The development of the catalog and cataloging rules", Library Quarterly, Vol.26 No.4, pp.254–75.
- Gordon Dunsire, Chris Pinder, (1991) "Dynix, automation and development at Napier Polytechnic", Program: electronic library and information systems, Vol. 25 Iss: 2, pp.91 - 103
- Automation Systems Installed Counting by Library organizations.
- Coyle, Karen (2011-07-25). "MARC21 as Data: A Start". The Code4Lib Journal (14).
- "WorldCat facts and statistics". Online Computer Library Center. 2011. Retrieved November 6, 2011.
Other sources 
- Chan, Lois Mai. Cataloging and Classification: An Introduction. New York: McGraw-Hill, 1994.
- Morelon, Régis; Rashed, Roshdi (1996), Encyclopedia of the History of Arabic Science 3, Routledge, ISBN 0-415-12410-7
- Svenonius, Elaine. The Intellectual Foundation of Information Organization. Cambridge, Mass: MIT Press, 2000.
- Taylor, Archer (1986) Book Catalogues: their varieties and uses; 2nd ed., introductions, corrections and additions by W. P. Barlow, Jr. Winchester: St Paul's Bibliographies (Previous ed.: Chicago: Newberry Library, 1957)
- Hanson, James C. M. Catalog rules; author and title entries (Chicago: American Library Association. 1908)
|Wikimedia Commons has media related to: Card catalogs|
- A general overview of the ISBD
- History of the card catalog article at LISWiki, a Library science wiki
- Very Innovative Webpacs — Online catalogs using particularly good design or functionality
- Libraries Australia — Australian national bibliographic catalogue: 800+ libraries
- OCLC WorldCat
- Resource Description and Access (RDA)