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Reading Call Numbers

What are call numbers & what do they mean?

Think of Call Numbers like an address - they describe the location of a physical item.

Call numbers are assigned with a lot of care and moving parts - the letters and numbers are not random, but represent various elements of each individual item. The lines represent subjects, genres, authors, and more, and are assigned to group items together that are in the same topic.

You do not need to know what each line means in order to locate an item in the library, but it helps to know how to break them down.

Click on the tabs to the left for specific examples (with photos) demonstrating how to find materials in Waldo Library.

*Please note that most, not all, of Waldo Library's materials are housed according to the Library of Congress Classification System.*

Here are some helpful links included in the rest of our guide, all in one place:


  • How do I get help if I can't find what I'm looking for?
    • There are MANY different ways! You can ask an employee roaming around (we have name tags on to indicate we are staff) with assistance, or contact us online via libchat, text, email, or phone.
  • What if I pick up a book and decide I no longer want it?
    • Place any items you do not wish to check out in the bins located at the end of the stacks, or bring them up to the front desk.
  • How do I check out a book from the library in-person?
    • Bring your item(s) and your Bronco card to the atrium to check your materials out. There is a self checkout machine right next to User Services, or you can walk right up to the Service desk and staff will help you. 
  • What system does our Archives and Special Collections use?
    • Please note that many of our facsimiles, manuscripts, fiction and non-fiction are arranged by the LoC system.
    • In special cases, like our collections housing Historical Children's Literature, Mini-books, art-books, and more, check out the last tab of this guide for more detail.
  • What does "OVERSIZE" at the top of a call number mean?: 
    • This means the physical copy of this item is too large to fit on the regular shelf, and will likely be placed at the bottom of the shelving unit nearest to it's call number range.
  • What does "C.1" at the bottom of a call number mean?:
    • A "C" with a decimal and a number attached to it indicates the copy number of an item. We may have multiple copies of certain materials, depending on how popular and well used they are.
    • All copies are the same item, one copy should not be different from the original.
  • What does "V.1" at the bottom of a call number mean? 
    • "V" with a decimal and a number indicates the volume number. Shakespeare's works sometimes have volumes 
  • Why do some subjects (such as geography and music) match their assigned letters, but some don't?
    • The LoC constructed their call numbers inspired by the Cutter Classification System. You can check out the wikipedia page via the link to the Cutter page to see why each line is broken down the way it is.
    • First line is subject, second referes to author, third typically indicates dates and editions, etc...
  • Why don't academic libraries use Dewey?
    • There are various answers to this question, but perhaps the main reason as to why many large U.S. academic institutions use LoC is because the Dewey Decimal System (DDS). when it was first developed, did not completely encompass all of the various subjects that grew in larger institutional libraries. Computer science, for example, was hard to put into DDS category, and the more sub-sections that were tacked on to different headings and subjects, the longer and more confusing the call numbers became.
    • LoC is more often used in larger institutions specifically because it is more descriptive of subject headings.
  • How do I use library search to even begin looking for a book?