Library Services for Students

1. The first line of a Library of Congress call number may begin with one, two, or three letters. Read these letters alphabetically. A call number that begins with A is shelved before one that begins with B, C, etc.; a call number that begins with QE is located before one that starts with QL.

   QE

   comes  before

   QL

2. The second line is a number that may have one or more digits. Read these as whole numbers. Therefore:

   HD  98

   comes before

   HD  587

   comes before

   HD  1001

3. The third line combines a letter and numbers. This is the tricky part of the call number! The letter is shelved alphabetically, and the numbers after the letter are decimal numbers.. Note the decimal point before the letter--it's like a reminder that the number is a decimal! Therefore:

   QE  352  .C444  1999

   comes before

   QE  352  .C64  1999

   comes before

   QE  352  .C7  1999

   comes before

   QE  352  .C754  1999

   This order makes sense if you read the numbers as decimals.

   0.444

   comes before

   0.64

   comes before

   0.7

   comes before

   0.754

4. The final lines of Library of Congress call numbers may include:
   • Another combination of letter and numbers (the "S46" in the example below). Although there's no decimal point, keep reading the numbers as decimals (in this case, 0.46):

     HQ  784  .I58  S46  2005

   • Publication Date (the "2005" in the example)
   • Volume or issue numbers
   • Copy numbers
   • Other annotations (for example: "supplement")

(This description was derived from a tutorial created by Humbolt State University Library.)