Part 4 Search‎ > ‎4.3 Books‎ > ‎

4.3.2 Call Numbers

To find an item in the library you need to know the call number. The call number serves as an address. It tells you both the location and subject of the item.


Most academic libraries in the U.S. use the Library of Congress Classification system to organize their collections. Public and school libraries primarily use the Dewey Decimal Classification system.

The classification system is a way to shelve items on the same subject in the same area. Take a look at the Library of Congress (LC) Classification Outline. Look for the blue LC Classification Outline posters in the library to help you with browsing the collections.

How to read an LC call number

A call number includes a classification number on the first line and alpha-numeric numbers beneath that.

Here is the call number of Plants in Hawaiian Medicine by Beatrice H. Krauss.
  • The first line stands for Hawaiian history.
  • The second line includes the initial of the author's last name and a number. (The letter might also be the first letter in the title or an editor's last name.) 
  • The last line is the publication year.
On the shelf, books are shelved first in alphabetical order according to the letters and numbers on the first line, and then by the letters and numbers on each line below.

Notice that there is a period before the author's initial and number. This is a decimal point. It means the numbers on that line are decimal numbers. If two books begin with the same classification number, the smaller decimal number comes first.


When two call numbers start with the same numbers on the first line, which comes first?