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Understanding Library Call Numbers: Home

Tips on deciphering Library call numbers in order to locate Library materials.

Call numbers

What is a call number?

The 'address' of a book within a library, assigned according to the subject of the book.  The Drew Catalog will list the call number of any item, which will also be on the spine of the book.

There are three systems of call numbers used by many libraries:

  • Dewey Decimal - usually used in public and school libraries.
  • Library of Congress - more commonly used in college libraries
  • SuDoc (Superintendent of Documents) - for documents from the federal government.

How do you tell the difference?

  • Dewey Decimal always begins with a number: 
  • Library of Congress always begins with letters: 
  • SuDoc always begins with letters, but contains a colon:  

Dewey Decimal always begins with a number: 

In both Dewey and LC, after the subject classification number, there is always a second line or element in the call number, beginning with a letter:  C368s, B64, etc.  This is generally refered to as a Cutter number (after the person who developed the system), and simply serves as a means of alphabetizing either the author or, if the work is about a person, the subject's name.

Dewey Decimal:  Call numbers are arranged first numerically, and then, within a specific number, alphabetically.  Notice that decimals count!

   390

   390.04

   390.13

  390.3

   390.38

Within a Dewey number, the second line is shelved alphabetically, and then numerically.  Even though there's not a decimal next to the Cutter number, it is implied in the order in which numbers are arranged on the shelf:

   390.3 
   B348j

    390.3 
    B42c

    390.3 
    B532j

    390.3 
    B619c

    390.3 
    B63a

Library of Congress always begins with letters: 

In both Dewey and LC, after the subject classification number, there is always a second line or element in the call number, beginning with a letter:  C368s, B64, etc.  This is generally refered to as a Cutter number (after the person who developed the system), and simply serves as a means of alphabetizing either the author or, if the work is about a person, the subject's name.

Library of Congress:  Call numbers are arranged first alphabetically, and then by the numbers that follow the letters.  On the first line, remember the rule, nothing comes before something:

   P

      PC

      PF

     PG 

After the initial letter(s), LC numbers are arranged by the value of the entire number:

   HQ 
    13

    HQ 
    35.2

    HQ 
    113

    HQ 
    734

   HQ 
    1073

After the first two lines, call numbers are arranged first alphabetically, and then according to the decimal:

   HQ 
   1073 
   .F46 
   2008

    HQ 
     1073 
     .F557 
     2009

    HQ 
     1073 
     .F61 
    

    HQ 
     1073 
     .J36 
     2004

SuDoc always begins with letters, but contains a colon:  

SuDoc:  Call numbers are arranged first alphabetically, with letters coming before numbers, and then numerically.  The only real tricks are to ignore "Senate Hearing" or "Senate Print," and to remember that what looks suspiciously like a decimal point in a SuDoc number is actually only a divider (as are any punctuation, such as / or :):  treat as whole numbers any numbers that follow punctuation:

  Y4. 
   F49: 
   Ai52

     Y4. 
     F49: 
     103-86

     Y4. 
     F49: 
     Senate Hearing 103-87

     Y4. 
     F49/20: 
    Z64

     Y4. 
     F49/20: 
     108-6

     Y4. 
     F76/1: 
     109-10

 

Where are the call numbers found in the Library?

  • Dewey Decimal books are on various floors. Check the Library Map to see where the specific number is.
  • Library of Congress books are currently located on two floors:
    • A-BY is on Level F
    • C-HD is on Level D
    • HE-Z is on Level C, behind the Atrium, on the far side of the Reference Collection.
  • SuDoc is primarily on Level A.

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