How to Read a Call Number

• Classification Systems
• What Are Call Numbers Used For?
• How to Read a Library of Congress Call Number
• Don't Put Books Back on the Shelf

Classification Systems

Library of Congress Classification System: Most academic libraries, including Pima College and the University of Arizona, use the Library of Congress (L.C.) classification system.

For example: the L. C. call number for "The Life and Times of Mark Twain" by Dennis Welland is PS1331.W4 1991.

Dewey Decimal System: Public and school libraries, including Tucson-Pima Public Library and the local Tucson high schools, use Dewey Decimal call numbers

For example: the Dewey Decimal call number for "The Life and Times of Mark Twain" by Dennis Welland is 92.T11we.

Music Classification at Pima College: Pima Colleges uses a unique music classification.

What Are Call Numbers Used For?

Each item in the library has its own call number. Each call number is unique, like an address for a house. Call numbers tell us exactly where the item is located on the library shelves. They also make finding information easier by grouping items on similar subjects together.

How to Read a Library of Congress Call Number

Most call numbers appear on the spine or the back of the book or video. Sometimes call numbers appear on the lower left corner of the front cover of an item. Call numbers are read from top-to-bottom.

Examples of L. C. Call Numbers

Top Line
The top line of the call number is the major subject. Books are arranged in alphabetical order based on the top line.

• A comes before AC (A = General Works)
• AC comes before B
• BF comes before BX (B = Philosophy, Psychology and Religion)
• Q comes before TD (Q = Science; T = Technology)
• TX comes before Z (Z = Bibliography, Library Science)

Second Line
The second line of the call number is a sub-classification of the major subject area. Works with the same top line are arranged in numerical order based on their second line.

The second line may be followed by a related line that is a decimal number. These decimal numbers are used to further organize large subject areas. When trying to locate a decimal number, it can be helpful to add an imaginary zero. For example, .76 comes before .80, which is the same as .8

Third Line
The third line of a call number is a combination of a letter and number called the Cutter number.  It is used to designate the author or artist's last name, geographic region or other information.

Read the letter portion alphabetically. Read the number portion as a decimal. When trying to locate an item it can helpful to add an imaginary zero. For example, .A23 clearly comes before .A30, which is the same as .A3

• .C2 comes before .E2

• .L34 comes before .N34

• .A23 comes before .A3
  

There may be more than one line that combines letters and decimal numbers. Read the letter alphabetically and the number as a decimal for all such lines.

Last Line
The last line may be a date. Dates are shelved in chronological order. If one book has a date and one does not, the book with no date comes first.

Don't Put Books Back on the Shelf
If you pull an item from the library shelves and don't want to check it out, leave it either on a table, at the end of a shelf or at the circulation desk. We want to count each item so we can see which areas of the library are being used. We also want to make sure the item goes back on the shelf in the exactly the right place; a misshelved item is a lost item.