How to Find a Book on the Shelf

Most of the books located on the shelves in our library and learning commons are arranged using call numbers based on the Library of Congress Classification System.  A book’s Library of Congress call number is located near the bottom of the book’s spine.

In the Library of Congress Classification System, books are arranged by subject.  Each book is assigned an alphanumeric call number based on its main focus or subject.  The call number acts as a unique identifier for each book, with books placed on the shelves near other books related to the same subject. 

When you look up a book in Primo, if it is a book we have in print format that we own at BCTC, you usually can find it on our shelves using the Library of Congress Classification System.

All Library of Congress Call Numbers begin with letters that represent various subject areas.

 LC Classification, Main Subject Classes:

The main subject classes often are narrowed even further by the addition of a second letter, called a subdivision.  For the full listing of the main classes and their subdivisions, see the Library of Congress site.

How to Read a Call Number:

Let’s start with a sample call number:  QL737.M336 O83 2004

This call number will lead you to a book with the title Tasmanian Tiger, by David Owen.

The first letter, "Q" represents one of the main subject classes listed above.  In this case,  the main subject is Science.  Items are shelved by this letter first, in alphabetical order.

The second letter "L" represents a subdivision of the sciences, Zoology. On the shelf, books with the subdivision of QL would be in the "Q" section, and then arranged alphabetically within that  Q section  (QL books would be shelved after any QK books we own, and so on).

The numbers following the letters are classification numbers (in this example the numbers 737).  In combination with the class and subdivision, the classification number further narrows the subject matter.  These are read as whole numbers, so QL737 would come after QL700 but before QL800.

The next piece of information, the M336,  is called a cutter number. The letter part of the cutter is read alphabetically. However, the numeric component of a cutter number is always read as a decimal, so in this case the M336 is really read as M.336, and M336 would come somewhere after M3 but before M4  

If necessary, a second cutter may be included in a call number, also (in this case, the second cutter is O83).  It is read in the same way as the first cutter, as a way to further narrow down the location of the book on the shelf.

Folllowing the cutter number(s) you often will see the year of publication.  In this case, that would be 2004


Now that you have the basic information about how a call number is arranged, you can begin to use it to find books on the shelves. Also, if you are new to the Library of Congress system, please don''t hesitate to ask a librarian to help you get started and show you how to find something. We are happy to help!

Our reference collection items, as well as our audiovisuals,  are separated out from the main book stacks, although they still are arranged on their designated shelves using the LC classification system.  Ask a librarian if you need assistance in locating those shelves in the library or learniing commons.

We do not use the LC classification system to arrange our periodicals. Instead, they are arranged alphabetically by journal title.  Newer issues of journals and magazines are displayed up front, while any older issues we have can be found in a separate periodicals shelving area.

Sometimes, you will see an item in the catalog listed as being located in the "Popular Collection."  These titles (leisure reading paperbacks, audiobooks, etc)  are located on a separate shelf in the library or learning commons. They are arranged alphabetically by authors' last names.

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What about Browsing?

Sometimes, you may just have a general topic in mind and it can be useful to browse the shelves in the general subject area you are interested in. You are welcome to do so.

You may find it useful to refer to the LC Main subject classes and subdivisions to help you get started. Charts with Library of Congress subject classification information are posted on some of our library book stacks for quick reference.

You also might consider examining some of the books on the shelves nearby a book you find; sometimes it can be worth it to browse nearby books. Because most of our books are arranged by subject, often there are  several useful, related books located near each other.