San Francisco Public Library


Dewey Decimal Classification

San Francisco Public Library uses the Dewey Decimal Classification to organize the materials in its collections. All nonfiction books and audiovisual materials are given classification numbers which represent their specific subject content. The aim in assigning classification numbers is to shelve together materials on the same subject. The Dewey Decimal Classification (or Dewey Decimal System) was developed by Melville Dewey in 1876. It has been modified and expanded through twenty-two revisions, the last one in 2004. The system is made up of ten main classes or categories, which in turn are divided into ten secondary classes or subcategories, each having ten subdivisions of its own. The ten main categories are: