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Guide to Dewey Decimal Classification

Understanding the Dewey Decimal Classification system which is used to organise books in the Library.

Guide to Dewey Decimal Classification

The books in the library are arranged on the shelves using the Dewey Decimal Classification (DDC). It is the most widely used library classification system in the world. The word “Dewey” refers to Melvil Dewey (1851-1931) who devised the classification, and was first published in 1876. The second word “Decimal” refers to the base-ten notation that is used to denote and relate subjects. It uses Arabic numerals treated like decimal fractions. Hence the name of the classification is the Dewey Decimal Classification. It is continuously revised to keep pace with knowledge.

Within each area of the Library, the books are shelved by classification number. The classification number (also called the class number or shelf number) appears on a label on the spine of the book. It is made up of the Dewey number and the first three letters of the author's surname or the first three letters of the title, whichever is the main entry on the catalogue. Books are placed on the shelf in increasing numerical order of the Dewey number. When two books have the same Dewey number they are arranged in alphabetical order of the first three letters from the author's name, or, first three letters from the title of the book. The end of each row of shelves indicates the numbers contained in those shelves.

The Library Catalogue will tell you the exact Dewey number of each book. 

Main Classes

  • 000 Computer science, information & general works
  • 100 Philosophy & psychology
  • 200 Religion
  • 300 Social sciences
  • 400 Language
  • 500 Science
  • 600 Technology
  • 700 Arts & recreation
  • 800 Literature
  • 900 History & geography

Dewey is further divided into 10 branches that are called divisions


Have you ever wondered how the numbers are built? Hierarchy in Dewey Decimal Classification is expressed through structure and notation. Notational hierarchy is expressed by length of notation.

See the following example:
300 Social Sciences
330 Economics
332 Financial economics
332.4 Money
332.41 Value of money
332.414 Factors affecting fluctuations in value
332.4142 Devaluation