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Dewey Decimal Classification: Home

A guide to the Dewey Decimal Classification Scheme

This library uses the Dewey Decimal Classification scheme (DDC) to arrange books and other library materials on the shelves so they may be easily retrieved. It is used in many libraries and allows items about the same subject to be shelved together.

Who was Dewey?

Melville Dewey, was born on December 10, 1851 to a poor family living in a small town in northern New York. He is known as the Father of Librarianship because he devised the system that is commonly used in many Libraries in the world. 

While working at his college Library, he saw the limitations of the current system of classification in Libraries. Classification systems used a fixed design where each book was given a dedicated spot on the shelf. This meant that when items were added to the collection, the whole lot changed position on the shelves and things became out of order. Another problem was that no two libraries used the same system, making it awkward for users and librarians to use different collections.

Dewey devised a system of decimal numbers to categorize books according to subject. He received permission from Amherst College, where he was studying, to apply his new system to their library. Amherst published his system in a pamphlet entitled A Classification and Subject Index for Cataloguing and Arranging the Books and Pamphlets of a Library in 1875 which is now in its 22nd edition and contained in four volumes.

How does the Dewey Decimal system work?

DDC is a hierarchical number system that organizes all human knowledge into 10 main categories. These are:

000      Generalities (includes computing)

  1. Philosophy and psychology

200      Religion

300 Social sciences

400      Languages

500      Natural sciences and mathematics

  1. Technology (applied science)

700      The arts

  1. Literature

900      Geography and history


Each main category is then divided into 10 sub-categories.  For example:

  1. Social sciences

310   General statistics

320   Politics

330  Economics

340   Law

350   Public administration

360   Social services

370   Education

380   Commerce, communications, transport

390   Customs, etiquette, folklore

Each sub-category is then also divided into 10 specific topics. For example:

                                    361      General social problems

                                    362      Social welfare problems and services

                                    363      Other social problems and services

                                    364      Criminology

                                    365      Penal and related institutions

                                    366      Associations

                                    367      General clubs

                                    368      Insurance

                                    369      Miscellaneous kinds of Associations                         

Each of these topics may be further divided into more specific subject areas. A decimal point is used after the first three digits to separate the specific subjects - it also makes the numbers easier to read. You will see that as the subject becomes more specific, so does the numbering. For example:

  1. social work

361.322 Interviewing

361.323 Counselling

DDC at West Suffolk College

When an item arrives in the library it is assigned a DDC number, often called the “classmark” or “shelfmark”. Each of the numbers in this classmark has a meaning and is not assigned randomly.

For example, the book “The Lure of dreams: Sigmund Freud and the construction of modernity” by Harvie Ferguson is assigned the number 154.63 FER

  1. Psychology
  1. Subconscious and altered states
    1. Sleep phenomena
    2. Dreams

Most items will also be assigned some letters at the end of the numerals, “FER” in the above example. These are taken from the author’s surname.

Finding items on the shelves

The classmark will always have at least three numbers, followed by some letters. It is usually displayed on the spine of the item.   The DDC system places items about the same subject at the same number. This means that once you have identified the DDC number for the subject you are interested in, you can browse the shelves at that number.


On each shelf the items are arranged in a numerical sequence from left to right by their DDC number. Where several items have an identical DDC number, the letters are used to further arrange them. For example,

361.                 361.                 361.                 363.                 363.                 363.

3                      32                    32                    35                    377                  377

HIG                 BOR                STO                CIV                  PRE                PRO

Finding e-books

Simply click on the link in the catalogue record or in Library+ – you don’t need to find it with class number because it won't be on the shelf!