The Dewey Decimal Classification System is detailed and features more than 1,000 possible categories. The system has 10 main categories, known as classes. The classes are subdivided into 100 categories, known as divisions. The divisions, which consist of 1000 sections, can be divided even further.
The Dewey Decimal System allows for the classification of library materials. Each item receives a number based on its class, division and section. For example, a book on the history of Japan receives a call number of 952. Its class is 900, which is reserved for history and geography materials. Call numbers between 950 and 959 are assigned to items regarding the history of Asia, and 952 is the number for the history of Japan.
Some libraries with large collections use the numbers to the right of the decimal point to provide a more precise means of locating a book. For example, a book regarding the history of Tokyo in the 20th century may receive a call number of 952.135033.