Week 11: Understanding the Dewey Decimal System

Understanding Dewey Decimal Call Numbers

Perhaps you have heard of the Dewey Decimal System (DDC), it is one of the systems libraries use to organize our books and periodicals. Without a system, it would be difficult to locate materials in large collections. When you visit your public library, such as Glendale Public Library, all the books are arranged using the DDC. Before I went to library school I just thought Dewey was an old name to call the system but it is named after its creator, Melvyl Dewey Links to an external site.. I got my MSLS (Masters of Science in Library Services) from the school he started to train professional librarians (1887 - Columbia University). 

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Libraries assign a unique number to each book in their collection. This unique number is known as a call number and is used to distinguish the item from all other items in the library. In addition, the call number indicates the main subject of the book and therefore, where the item will be shelved in the collection. A label containing this call number appears on every item in the library, usually on the spine. The exception in the GCC Library is print periodicals, which are shelved alphabetically by title.

The Dewey Decimal Classification (DDC) Links to an external site. system uses call numbers that are a combination of letters and numbers. (Note: the other popular call number system is the Library of Congress (LC) classification Links to an external site. system; it also uses a combination of letters and numbers used mainly in higher education collections).  The first part of each call number organizes materials by subject. Every DDC call number begins with a three-digit whole number, and most titles in the GCC Library are followed by decimal numbers. The second part of the DDC call number uses letters and numbers in combination. In the library catalog, a space separates the parts of the call number. On the book label, the first part is usually above the second part.

Examples of DDC Call Numbers:

Title	DDC Call Number
The annotated U.S. Constitution and Declaration of Independence	342.7302 A615
American Historical Documents	973 A512
Inventing America: Jefferson’s Declaration of Independence	973.313 W741i

Example: Inventing America: Jefferson’s Declaration of Independence by Garry Wills   

973.313
W741i

The first line of a DDC call number identifies the subject of the work and each digit has a specific meaning. In this example, the digits have the following meaning:

1. 1. The first number, 9, places the book in the 900s which is History & Geography,
   2. The second number, 7, places the book in the 970s which is General History of North America,
   3. The third number, 3, places the book in the 973s which is United States,
   4. The fourth number, 3, places the book the in 973.3s which is Revolution and confederation, 1775-1789,

Thus 973.3 is used for materials about the American revolution and confederation which occurred between 1775 and 1789.

The second line of the call number identifies the author of the work by using the first three letters of the author's last name, or the corporate name. In this example, the author is Garry Wills, so the first three letters of his last name are used, Wil.

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DDC Call Numbers in Alpha-numeric Order:

Reading Call Numbers:

When reading a call number, note that the number that comes before the decimal is a whole number, and everything that follows it is a decimal number. Therefore, 091 comes before 910, and 940.13 comes before 940.3.

098 Ha

973.3 Wil

976.3 H773c

976.4 Web

977.5 B586n

977.5 Gar

978.8 Abb

978.9 G664t

You DO NOT need to memorize the Dewey Decimal System. It is important to notice, however, that similar materials are often grouped together on the shelf. This makes it easier to browse for useful books.

Note that call numbers usually appear differently on the spine of the book.

On the book in the stacks*, the above call number would be shown as:

547.758
P176u4

(* stacks is another name for bookshelves in libraries). 

To find this book:
Understanding Enzymes by T. Palmer (call number 547.758 P176U4):

Locate the first three digits (547).

1/2. Locate any digits following the decimal point. Remember that it is a decimal system, so 547.8 comes after 547.75 and 547.758.

3. When you have located the number in full, look for the letter, then the next set of numbers.

4. Check that the last letter and number are correct, to make sure you have the right book and edition.

How to use the Dewey Decimal System Links to an external site. Shay Hendricks

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Melvil Dewey Links to an external site., the inventor of the Dewey Decimal classification

Since the DDC system was developed in the 19th century, world views have shifted Links to an external site.. 

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