Because libraries usually contain a vast amount of material, users might never find the information they need if this material were not carefully organized. For this reason librarians have developed systematic procedures to organize their collections in ways that provide users with convenient and logical access to materials. Although no two libraries are organized in exactly the same way, nearly all libraries use some type of system to catalog, or index, their collections. In addition, libraries use similar systems to classify and arrange their materials on library shelves. For these reasons, library users require a basic understanding of the common types of catalogs and the principles of classification to easily find the information they need. ACatalogs A library catalog is an index to the library's collection that enables a user to find materials. Library users can determine whether the library owns the materials they need by searching through catalog records. In many cases the information provided on the record will enable the patron to make a decision about whether the item listed suits his or her needs. Catalog records typically list the item's author, its title, its subjects, the date it was published, the name of its publisher, and other information. In addition, the catalog record contains the item's call number, a combination of letters and numbers used to classify the work. The call number also indicates the item's location in the library. For example, a book on architecture is classified-and arranged in the library-with the library's other books on architecture. Library catalogs may limit their listings to the items the library owns, or they may include listings for the holdings of other libraries as well. Library catalogs that list the holdings of multiple libraries are called union catalogs. Libraries list their holdings in several different kinds of catalogs, including book catalogs, card catalogs, microform catalogs, and computerized catalogs in either CD-ROM or online format. The majority of library patrons now use computerized catalogs. A1Book Catalogs Book catalogs list the holdings of the library in a catalog in book form. Libraries first introduced book catalogs in the late 16th century, and they remained popular for some 300 years. The book catalog features complete information about each item, usually under the name of the author. Alternate listings organized by title or subject usually contain brief descriptions of each item. Librarians consider the portability of the book catalog to be a major advantage. Book catalogs are also relatively inexpensive to produce in multiple copies. The book catalog's great disadvantage is that it is not easily updated; libraries must issue supplements to list new items that the library has acquired. Few modern libraries continue to publish book catalogs. A2Card Catalogs Card catalog entries are printed on cards that libraries arrange alphabetically in drawers. A card catalog usually contains three types of cards for each item in the library's collection. The first type has the author's name or other persons or institutions that contributed to the work on the top line, the second has the title of the book or other item on the top line, and the third has the subject of the item on the top line. Usually the subject heading is printed in all capital letters or in red for further emphasis. Each drawer in the library's card catalog has a label telling what letters are included in it. The card catalog largely replaced the book catalog in the late 19th century because it could easily be expanded by filing new cards as the library added new materials. In addition, more than one person could use the card catalog at any given time. The card catalog's acceptance was enhanced in 1901, when the Library of Congress began to sell copies of its catalog cards to other libraries. The card catalog system is still widely used, although its popularity began to decline when libraries adopted computerized catalogs. A3Microfiche Catalogs A microfiche catalog is similar in organization to a book or card catalog, but its format is different. Microfiche is a small sheet of film printed with rows of very small images that can be viewed using a library's microfiche viewer, which magnifies the images. A microfiche catalog allows libraries to store vast amounts of catalog information in much smaller spaces than printed catalogs require. Whereas book catalogs and a few card catalogs list complete entries only under the author's name, all entries in a microfiche catalog are usually complete. This means that each entry will contain the item's author, its title, its subjects, its call number, the date it was published, the name of its publisher, and other information. Despite this advantage, only a few library users can access the typical library's limited number of microfiche viewers at any given time. Although many libraries maintain microfiche catalogs, most rely primarily on their computerized catalogs. A4Computerized Catalogs Often referred to as online public access catalogs (OPACs) or online catalogs, computerized catalogs were first introduced in libraries in the early 1980s. Online catalogs provide broader access to a library's collection by allowing more sophisticated searching of the catalog. They are also updated easily. Using a computer, a modem, and telephone lines, they can be searched from locations outside the library building through the Internet. In addition, many libraries have integrated their online catalogs with their circulation systems, providing information on the status of a book's availability in the library in addition to the usual cataloging information. This useful feature has never been a characteristic of other catalog formats. Despite these advantages, libraries with small operating budgets have difficulty raising the funds to convert book catalogs, microfiche catalogs, or card catalogs into machine-readable formats that computers can use. A5Catalog Descriptions of Library Materials Librarians give careful consideration to the ways in which they describe their documents so that users can easily search library catalogs to determine whether the library has specific items. Rules for describing all forms of library materials are governed by cataloging codes developed at the national or international level. Cataloging codes set standards for the types of information that a catalog should include and for the format in which that information should be presented. By establishing consistency in the content and format of catalog descriptions, these standards simplify the user's search for library materials. In addition, standardized catalog descriptions enable libraries to easily share information about their collections with one another. In the United States, libraries first attempted to establish a standard for catalog descriptions in the late 19th century. Since then, libraries in the United States, the United Kingdom, Canada, and a number of other countries have adopted a standard set of rules for describing documents in their collections.
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