The Dewey Decimal Classification (DDC), or Dewey Decimal System, is a proprietary library classification system first published in the United States by Melvil Dewey in 1876. It has been revised and expanded through 23 major editions, the latest issued in 2011, and has grown from a four-page pamphlet in 1876. It is also available in an abridged version suitable for smaller libraries. It is currently maintained by the Online Computer Library Center (OCLC), a non-profit cooperative that serves libraries. OCLC licenses access to an online version for catalogers called "WebDewey". 

The Decimal Classification introduced the concepts of "relative location" and "relative index" which allow new books to be added to a library in their appropriate location based on subject. Libraries previously had given books permanent shelf locations that were related to the order of acquisition rather than topic. The classification's notation makes use of three-digit Arabic numerals for main classes, with fractional decimals allowing expansion for further detail. Using Arabic numerals for symbols, it is flexible to the degree that numbers can be expanded in linear fashion to cover special aspects of general subjects. A library assigns a classification number that unambiguously locates a particular volume in a position relative to other books in the library, on the basis of its subject. The number makes it possible to find any book and to return it to its proper place on the library shelves. The classification system is used in 200,000 libraries in at least 135 countries.
Who published the DDC? When? Where? Is DDC an acronym? What does it stand for? Is it called anything else? What concepts were introduced with this program? What criteria did it use to put the books in a location? What type of numerals did it use for main classes of books? 2 digit? How many? Were fractional decimals used as well? What did this allow expansion for? Was the use of numerals rigid? How was its use described? How many editions have there been? When was the last released? How many pages did it originally have? Who maintains the DDC now? Are they a private, for profit company?
Melvil Dewey 1876 the United States yes Dewey Decimal Classification Dewey Decimal System "relative location" and "relative index" subject Arabic no Three yes further detail. no it is flexible 23 2011, four OCLC no