Have you ever wondered how library books are assigned their places on the shelves?
Did you know that the call number—the number placed on the spine of the book—is a code which provides valuable information about the book?

This page will provide an introduction to understanding and using library call numbers.

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Why Are Call Numbers Necessary?

Each book in the library has a unique call number. A call number is like an address: it tells you where the book is located in the library.

Call numbers appear

Note that the same call number can be written from top-to-bottom, or left-to-right.

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Since the mid-70s the Howard University Libraries have been using the Library of Congress (LC) Classification system for call numbers. Before that time, the Dewey Decimal system was used.   Many of the older books in the Undergraduate Library still have Dewey Decimal call numbers. To view the Dewey Decimal chart,  click here  and  click here too see how Dewey Decimal call numbers are read.

The LC system uses a combination of letters and numbers to arrange materials by subjects.

Reading Call Numbers

Putting Call Numbers in Shelf Order

To understand how call numbers are put in order in Library of Congress Classification, again look at each section of the call number.

 

What Does the Call Number Mean?

Remember that Library of Congress Classification arranges materials by subjects. The first sections of the call number represent the subject of the book. The letter-and-decimal section of the call number often represents the author's last name. And, as you recall, the last section of a call number is often the date of publication.

Example:

Why Is This Important to Know?

Because books are classified by subject, you can often find several helpful books on the same shelf, or nearby. For example, within the same call number LB2395, there are other guides for college study.