A catalog (sometimes called a catalogue) is a list of items, usually in alphabetical order. It may be exhaustive, or selective. A library catalog, for example, is a list of all the books in that library. An inventory catalog is a list of all the assets owned by a business. A card catalog is an index to help find information in a larger set of documents, such as books in a library.
Some libraries use Boolean operators to allow patrons to narrow their search results when using the library’s online public access catalog (OPAC). For example, if one were looking for books about cats written by Mark Twain, one could type “cats AND Twain” into the OPAC’s search bar. This would give all results that contain both terms somewhere in their bibliographic record—items about cats that were also written by Mark Twain. Conversely, typing “cats NOT Twain” would give all results that mention cats but excludes those mentioning only Twain. The ability to use Boolean operators allows patrons greater control over their searches and can result in more precise retrieval of desired materials from OPACs.
Most libraries will have some sort of policy as to what types of items are included and excluded from their catalogs; for instance, most public libraries do not include items such as encyclopedias or dictionaries because they are considered reference works and are therefore available for use only within the library itself. The consistent application and enforcement of these policies is crucial to ensuring the accuracy and usefulness of any given catalog.