The Dewey Decimal Classification system is a library book and media classification system based on relative location and relative index that was created by Melvil Dewey in 1876. The system is currently maintained by the Online Computer Library Center and used by over 200,000 libraries in over 130 countries.
The Dewey Decimal system sorts books in libraries by their content or subject matter, rather than by author name or date of acquisition. It accomplishes this by assigning each class of books a particular three-digit number and using decimals to expand these classes into more detailed groups. The Dewey Decimal Classification system is the main classification system used in the world, but it has several competitors such as the Library of Congress Classification system and the BIASC bookstore system.