The University of St. Thomas

Reading call numbers

How to Read a Call Number

Call numbers are combinations of letters and numbers which provide information about where materials are located on the shelves and about the subject of the materials. Call numbers appear in the CLICnet catalog and on the spines or fronts of the books.  Call numbers in the University of St. Thomas Libraries are based on the Library of Congress Classification System.

Call numbers serve two main functions within a library:

  1. They provide a unique "address" for every item within a library, so that once you understand the structure of call numbers, you can find any item you are looking for; and
  2. they group items by subject, so that once you find one relevant item, you can browse the shelves around it to find other items on the same or similar subjects.
     

    Reading a Call Number

    General principles:

    • Read call numbers line by line, from left to right, and from top to bottom.
    • The first line is always the general location, which indicates in which library (building) you'll find it, as well as within which collection in the library: (UST-OSF indicates the O'Shaughnessy-Frey Library general collection; UST-OSF Reference is the the OSF Library reference collection on the first floor; UST-MRC is the Music Resource Center; and so on.  When you're looking at a record in the CLICnet catalog, you can click on the Location link to get more information about that location.
    • Group call numbers alphabetically first, then numerically.
    • Numbers following a decimal are read as decimals, regardless of whether there's a letter in front of the number or not.

    Looking at the earlier example, we can pinpoint its location as follows:

    What Does the Call Number Mean?

    Call numbers are more than a shelf location ? they also indicate the subject matter of an item. This allows libraries to shelve together books about the same topic, and makes it possible to browse the shelves for books on a topic, once you know the general call number area.

    For information on other subject areas and the relationship to call numbers, see ???

    The call number in the example above is interpreted in this way:

    UST-OSF Stacks OSF Library general collection  
    PN In OSF Library, call numbers between P and PR are on the 3rd floor; the PN call number section will come after call numbers beginning with P, PA, PB, PC, PE, PF, PG, PH, PJ, PK, PL, and PM P is the class for Language and Literature. PN is the subclass designation for general literature, including literary genres (e.g., poetry, short stories, novels, drama), journalism, theater, film, and television
    1995.9 Within the PN section, call numbers are divided numerically, from 1 through 9999, and may include decimals:
    PN
    1995.8    		 PN
    1995.9     		PN
    1996
    		PN1993-PN1999 = works on motion pictures
    PN1995.9 = general and special topics, including criticism and aesthetics, and is divided into specific topics, from A-Z
    .J6 A second decimal point includes both letters and numbers. These are read alphabetically first (e.g., A before B, followed by C), then as a decimal number:
    PN
    1995.9
    .J5    		 PN
    1995.9
    .J57    		 PN
    1995.9
    .J6     		PN
    1995.9
    .J67    		 PN
    1995.9
    .J7
    		.J6 indicates that the specific topic in this case is journalism; all other books in this section are on journalism in motion pictures
    E38 The next letter/number combination is also read alphabetically, then decimally:
    PN
    1995.9
    .J6
    D44    		 PN
    1995.9
    .J6
    E3    		 PN
    1995.9
    .J6
     E38    		 PN
    1995.9
    .J6
    F66    		 PN
    1995.9
    .J6
    G38
    		 Represents the author; this allows books on the same topic to be shelved alphabetically by author
    2004 If you get to this point and there's more than one book using the same call number, the date will help you poinpoint the exact copy Date of publication