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Devised by American librarian Melvil Dewey in the 1870s when he was 21 years old and working as an assistant in a college library, the Dewey Decimal Classification (DDC) is a system for organizing items in a library collection. It is the world's most widely used classification system and is used in over 200,000 libraries worldwide, including 95% of public and K-12 school libraries and 25% of college and university libraries. At CSU, it is used to organize the curriculum materials collection and the children's literature collection.
The purpose of a library classification scheme is to make it possible for users to easily find what they need on the library's shelves. It is similar to the concept in the non-library world of street names and house numbers which makes it possible to locate residences and businesses. The DDC is based on the concept that items on the same subject should be placed together for ease of reference, and it provides a logical system organized by subjects that covers the entire world of knowledge. It divides this world of knowledge into ten main classes, 100 divisions, and 1,000 sections.
| 000 Computer science, information & general
100 Philosophy & psychology
300 Social sciences
700 Arts & recreation
900 History & geography
The smallest numbers (only three digits long) are used to identify materials with broad subjects; larger numbers (created by adding digits after a decimal point) are used to describe narrower subjects. The use of numbers after the decimal point is what gives this system its name, its flexibility, and its usefulness in classifying a wide range of subject material.
Librarians determine appropriate Dewey numbers and mark each item in the library's collection with a "call number" which consists of the Dewey number for the subject matter and another number (called a Cutter number) that places the author or title of the book in alphabetical order. The items are then placed on the shelves in order by their Dewey numbers and then by their Cutter numbers. Occasionally a year will be added to the call number.
Examples of books in order on the shelves (reading from left to right) by their Dewey numbers and Cutter numbers:
For a very thorough explanation of the DDC and how it works, a tutorial, "Dewey to the Rescue," provides a tour of the DDC and is available at http://www.oclc.org/dewey/resources/tour/default.htm
On that page choose "Take the multimedia tour."
(Note: A Macromedia Flash Player Plugin (available here) is required for viewing).