Dewey Decimal Classification is the most widely used method of classifying books in a library. It is named for Melvil Dewey, who developed it in 1876 (see Dewey, Melvil). This system classifies books by dividing them into 10 main groups, each represented by figures, as in the table with this article.
Each of these 10 main classes is broken up into more specialized fields. For example, class 600-699, Technology, is subdivided into 10 special classes. Each of these divisions is further subdivided. The numbers 630-639, for example, represent Agriculture, and are subdivided into such classes as Field Crops, Garden Crops, and Processing Dairy and Related Technologies. When the classification becomes very fine, decimals are used to represent specific areas. For example, books on useful insects, such as bees and silkworms, are grouped under the number 638. Books on beekeeping are in 638.1, and those on silkworms in 638.2.
Not all libraries use the Dewey Decimal Classification. Many follow another system developed by the Library of Congress (see Library of Congress Classification).
