Understanding Call Numbers

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.

What are call numbers for?

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

Call numbers appear on the spine or front of the book.

[call number icon]  

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

The NJIT libraries, like many college and university libraries in the north America, uses Library of Congress Classification for call numbers. This system uses a combination of letters and numbers to arrange materials by subjects.

Reading call numbers

[call number 2 icon]  

To Re-emphasize:

LB 2395 is "LB two thousand, three hundred, and ninety five"

.C65 is "point C six five"

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.

[call number 3 icon]  

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.


[call number 4 icon]  

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.

call number 5 icon]

Since Library of Congress Classification arranges materials by subjects, knowing the letter(s) for your subject area gives you a place to start browsing the shelves. Which letters represent your subject? View the Library of Congress Classification table.

Location prefixes

When you find a book in our Voyager online catalog, the call number will be preceded by a location prefix.

  • Example:

  • Stacks (lower level) AG243 .G87 1992
  • The Stacks (lower level) prefix indicates that this book is shelved in the books stacks in the bottom (basement) level of the library.

Location prefixes mean that book is shelved in a special place, and may have loan restrictions. Here are some of the NJIT location prefixes:

  • Stacks (lower level)
  • Circulation Desk (usually Reserve material)
  • Disk (ask at the Circulation Desk)
  • Reference stacks (main floor, southeast corner)
  • ArchLib stacks (aisles 2 through 9)
  • Temporarily Shelved at Arch Desk

Points of learning:

  • Call numbers assign a unique number to each book
  • This places the book at a specific location on the shelf
  • Books will be on the shelves next to other books on the same or similar subjects
  • Location prefixes will first direct you to a specific section of the library

This web page adapted by the NJIT library from one done by the Honolulu Community College.