The Dewey Decimal System

What is the Dewey Decimal Classification System? Dewey Decimal Classification (DDC) is a way of organizing knowledge. It is the most widely used system for arranging library materials by subject, and the one most used by public libraries. The system gets its name from Melvil Dewey who created the classification in 1876. By classifying books by subject, all the books on the same topic will be found together on the shelves.

Why "Decimal"?
Dewey decided that all knowledge could be described in ten main divisions: for example...
000 Generalities 100 Philosophy & Psychology 200 Religion 300 Social Sciences 400 Language 500 Natural Sciences & Mathematics 600 Technology 700 The Arts 800 Literature 900 Geography and History
Organizing all knowledge into just 10 divisions obviously isn’t enough. Within each of the main divisions the system allows a further "ten category" breakdown:
for example...
700 The Arts 710 Civic & Landscape Art 720 Architecture 730 Plastic Arts Sculpture 740 Drawing & Decorative Arts 750 Painting & Paintings 760 Graphic Arts Printmaking & Prints 770 Photography & Photographs 780 Music 790 Recreational & Performing Arts
...and the system continues to get more and more specific.
After you work in the library you’ll start to become more familiar with the system and what number various topics have.

So how will all this help me find or reshelve books?
Think of the library as being divided into 3 zones (4 if you count the reference section), “Everybody” books, Fiction, and Nonfiction. If you know the call number of an item, you’ll know where to start looking. Within the Everybody and Fiction sections all books are in alphabetical order by the first three letters of authors’ last names. In the Nonfiction section all books are in numerical order by their Dewey numbers. Books that all have the same Dewey number are then further arranged alphabetically by the authors’ last names.