The Dewey Decimal Classification System

The Classification System  |  Finding a Book on the Shelves

The Classification System

Books in the library are arranged on the shelves according to the Dewey Decimal Classification System (developed by Melville Dewey).  This system, the most commonly used in school and public libraries, divides knowledge into ten different broad subject areas, called classes, numbered 000 - 999. Materials which are too general to belong to a specific group (encyclopedias, newspapers, magazines, library science, etc.) are placed in the 000's.

The Ten Main Classes of the "Dewey" System:

 000    Generalities
 100    Philosophy & Psychology
 200    Religion
 300    Social Sciences
 400    Language
 500    Natural Sciences & Mathematics
 600    Technology (Applied Sciences,
            including Medicine)
 700    The Fine Arts
 800    Literature & Rhetoric
 900    Geography & History

Subclasses

Specifying Subdivisions

 520      Astronomy & allied sciences
             523     Specific celestial bodies & phenomena
                        523.1         The universe
                        523.2         Solar system
                        523.3         The moon
                        523.4         Planets
                                          523.41              Mercury
                                          523.42              Venus
                                          523.43                Mars

• Classified according to the subject matter it covers (given the Dewey number).
• Three letters are added to this number. This represents the author's last name or the first word of the title (if the book is edited with no one author).
• The number indicates where  the book will be shelved in the library.

Study the following example:

 Name of book:       My Pet Hamster
 Author:                   Nigel Taylor
 Dewey no.:             636.93233 TAY

Explanation of the above Dewey Number:

 636                   Looking after animals
 .9                      Other Mammals
 3233                 Hamster
TAY                   First three letters of the author's last
                           name
 

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The above information was modified from a page developed at the Hewett School, Norwich, Norfolk, UK.  http://www.hewett.norfolk.sch.uk/COMMON/LIBRARY/dewey/dewey2.htm

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Finding Books on the Shelves Using the Dewey System

OK, so  now you know "what" the Dewey System is, but "how" do you locate the books on the shelves?

Let's look at our sample call number again

 636.93233
 TAY

In a small collection this might be fairly easy to find simply by browsing the shelves.  But in larger collections there are often range indicators (signs) on the ends of the shelf units which can help you move through the collection faster.

A good tip for finding your call number would be to remember "from greatest to most specific."

Following through with our example above, locate the general class of 600's first (the greatest), look next for the 630's, then the 636's.  Once you have identified the base number (636), then you need to identify the correct decimal location.  Decimals are read from the 10's place to the thousand's place.  For example:  call numbers containing .450 would precede call numbers containing .6 (even though .450 appears to be the larger number - remember, we're thinking in decimals here).  Consequently, all the numbers ending in .450 would proceed numbers ending with .451.

Following are call numbers arranged in the order that they would sit on the shelves:

636.04           636.3           636.450           636.5984           636.973

To further complicate the issue, if more than one book has been assigned the same call number (because they all fall into the same classification area, say 636.3), those books are then arranged on the shelf in alphabetical order by the author's last name (TAY in our example above).

The following call numbers are arranged in the correct order:

636.3            636.3           636.3          636.3           636.3
AGE             CAR              FOR             KNO            OLD

...where the capitalized letters indicate either the author's last name or the beginning word of the title.

Other Call Number Notations

Occasionally the material you have identified has other alphabetical notations preceding the Dewey number.  For an explanation of these, click here.
 
If you have questions at any time about locating materials in the library, be sure to check with the library staff!