Dewey Decimal System
The Dewey Decimal System has ten major subject groupings. Within each subject group, there are classification numbers that lead to more specific topics:
Overview
000 GENERAL KNOWLEDGE
100 PHILOSOPHY & PSYCHOLOGY
200 RELIGION
300 SOCIAL SCIENCES
400 LANGUAGES
500 SCIENCE
600 TECHNOLOGY
700 ARTS & RECREATION
800 LITERATURE
900 HISTORY & GEOGRAPHY