Skip to Main Content

Using the Library Catalog: Discover

Need help using the new catalog interface? Use the tabs to explore search tips.

What is a call number?

The call number of an item acts like a house's street address. It is a unique identifier that locates the item sequentially within a larger group of similar objects (much like the other houses on a block usually have a similar design, shape, size, etc).

  • Most books in the library are organized using the Library of Congress Classification system.
  • CDs, DVDs, and other items use a local classification system.
  • Many government documents use the Superintendent of Documents Classification System.
  • A number of items, notably art materials, some scores, and some other old materials continue to use the Dewey Decimal System

When you find an item in the catalog you want to use, you must make a note of the call number and either look for the item on a shelf or, if the item is located within closed stacks, request the item, either from a staff person at a desk, or using a remote-storage request form. In both latter cases you will need to provide us with the number.

Arrangement on shelves

Most items in the libraries are located on shelves that you can browse. While most books are freely accessible, several media types (notably films and audio recordings) are on shelves accessible only to staff.

When you are trying to locate an item on a shelf you will usually find a sign located on the end of the shelf that indicates the range of call numbers that can be found on that row. Maps are also available online and on the floor to help you find the shelf you need.

A shelf consists of sections and is arranged from lowest to highest call number, with the lowest values appearing at the top and left of a shelf section, and higher values falling towards the right and bottom. For every section, the order of items repeat this pattern.

diagram of arrangement of call numbers on shelves

Call numbers for books

Most books are organized using the Library of Congress Classification System (sometimes abbreviated as LC Call Number, LC Control Number, or LCCN), an alphanumeric system that organizes items by subject.

Each book will have a series of letters and numbers. On a computer screen these typically appear in one line and are read from left to right:

  • B 358 .C3 1997
  • HB 74.P8 L479 2006
  • QK 46.5.H85 P66 2001 c.2

On the spine of a book they are also read left to right, but also top to bottom. Taking the third example above:

  • QK
    c. 2

Reading Library of Congress Call Numbers

The first group of letters

The group of characters consists of letters (typically one or two letters, and very rarely, three) indicates the subject of the book. Call numbers starting with single letters (representing broad subjects) are shelved before double letters (representing subdivisions within a broad subject).

B | BD | BF | D | GA | H | HF | K | KB | KBM

There can be thousands of books within each division/subdivision, and so B and BD may be several shelves apart from one another. Similarly, items starting with P may be on a different floor or in a different building, altogether.

Next: numbers

The second part of the call number is read as an integer. Lower values fall to the left of a shelf, higher values to the right. This number further subdivides the subject indicated by the letter(s) above.

ex. From left to right on a shelf: 40 | 45.2 | 106 | 150.2 | 260

Tip: When you locate a book on a shelf, scan the titles to the left and right, chances are there's something nearby that is quite relevant to you!

Next: a combination of letters and numbers preceded by a "."

This group of letters and numbers typically identify the author and is called the cutter. Read the letters alphabetically and treat the number as a decimal, with lower values falling to the left and higher values to the right.

ex. From left to right: .C72 | .D3 | .D35 | .E66

Note that there may be more than one combination of these letters and numbers for an item. ex. NC 345 .B45 .C96 2007

Next (often last): the year of publication

Read this line as a year, i.e. 1988 | 1989 | 1990

Additional copies

In some cases the library will own several copies of an item. In these cases the item will usually have the same call number but the copy will have a trailing "c. 2," where the number is the copy number.

Read more information about Library of Congress Classification, used for the leftmost parts of a call number.

Multimedia (CDs, VHS, DVDs, games) & Reserve items

Many items that are retrievable only by a library employee will have a "local" call number. Typically these look more like natural/understandable identifiers for an item. Simply note the call number and provide it to the employee at the noted location. The following list of examples is provided for your convenience, however it is not comprehensive:

Item Type Local Call Number Prefix Example
Media Library
Albums Ph-disc Ph-disc 114
Audio CD ACD ACD 20
Audiotapes Ph-tape Ph-tape 1005
Digital Audio Book ADB ADB 5
Filmstrips F.S. F.S. 357
Games Game Game 27
Laser Discs LD LD 170
Motion pictures (16mm film) MP MP 496
Slides Slide Slide 243
Video Recording (VHS) MV MV 4826
Music Library
Audio CD LPCD LPCD 2045
Records (LP) LPZ or LPY LPZ 123
Music DVD MDVD MDVD 00742
Cassette Music Cassette Music Cassette 456
Reserve Items* Some reserve materials will have LC Call Number
Sycamore Library Reserves ECR ECR 12593
Willis Library General Reserves GRW GRW 112
Music MUR Personal Copy MUR
Discovery Park Reserves RPR RPR 123

Call Numbers for Government Publications

Government publications are classified using the Superintendent of Documents Classification System (SuDocs). Each document is classified by an institutional author (such as a government agency or commission) that is notated by a combination of characters that proceed a colon character. Characters that occur after the colon indicate the book number of the item.

Ex SuDocs Number: I 29.9/5 : 156
I = Department of Interior
29 = National Parks
9 = bibliographies and lists
5 = type of bibliography
156 = the book number

More comprehensive information about SuDocs numbers

Additional Links