The Dewey Decimal system is a classification system used by libraries to arrange books via subject. Each book is issued a shelfmark number, usually found on the spine of the book, and arranged in numerical order.
- 000 Computer science, Information General Works
- 100 Philosophy, Psychology
- 200 Religion
- 300 Social Sciences
- 400 Language
- 500 Technology
- 600 Science
- 700 Arts
- 800 Literature
- 900 History & Geography
The first three digits refer to broad subject area, and are shelved in numerical order e.g. 745 is shelved before 746.
After the three digits there is a decimal point and numbers after the decimal point show the sub-section of the subject area. Again they are shelved in numerical order e.g. 746.094 is shelved before746.62.
After the numbers there are three letters which refer to the author or editor of the book and are in alphabetical order e.g. 946.62 FOG is shelved before 946.62 INN.