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 and general work |
| 100 | Philosophy and psychology |
| 200 | Religion |
| 300 | Social sciences |
| 400 | Language |
| 500 | Science |
| 600 | Technology |
| 700 | Art and recreation |
| 800 | Literature |
| 900 | History and geography |
How does the Dewey Decimal System work?
The first three digits refer to the broad subject area, and are shelved in numerical order. For example, 945 is shelved before 946.
The three digits are followed by a decimal point. The numbers after the decimal point show the sub-section of the subject area. Again, they are shelved in numerical order. For example, 945.805 is shelved before 945.81.
After the numbers, there are three letters which refer to the author(s) or editor(s) of the book. They are shelved in alphabetical order. For example, 945.805 TAB is shelved before 945.805 TRB.
We also use the Dewey Decimal System for journals (sometimes called periodicals). Journals always start PER, followed by three numbers and the first three letters of the journal series. For example, PER720 ARC, which refers to the Architectural Review. Medical journals follow the same ordering, but start MED PER.
