The Dewey Decimal Classification (DDC) System was developed by Melvil Dewey in 1876. It is now used as a way to organize non fiction books and other resources in libraries through out the world. There are ten main subject categories that can extend into divisions and sections. It can be as simple or as complex as needed but the main purpose of Dewey is to organize so that you can find what you need.
The 10 main Dewey Decimal categories are below:
100--Philosophy and Psychology
500--Natural Sciences and Mathematics
600--Technology (Applied Sciences)
700--Arts and Recreation
900--Geography and History