Answered By: Laurel Angrist
Last Updated: Mar 07, 2016     Views: 16

A call # is an address for a book or other type of library material. College libraries use Library of Congress Classification, which begin with letters of the alphabet. Each letter stands for a broad subject grouping; each letter and number that follow the first letter narrow down the subject. No two books have exactly the same call number. The entire call number should be noted in order to locate the item.

How to read Call Numbers:

LC call numbers are first arranged alphabetically, according to the letter or letters at the beginning of the call number, which correspond to the subject matter of the item.
Example: Call numbers beginning with P are followed by PA, PB, PC, etc.

Within the alphabetical section, books are arranged by the number(s) that follow. Notice that these numbers are regarded as whole numbers. For instance, PS 1200 comes after PS 345.
Example: QA 56 before QA 234 before QA 234.57 before QA 234.8

The next lines are alphabetic, then numeric as a decimal. The numerical part of this section is a decimal number, not a whole number. Use alphabetical order first, then the decimal extension to put the call numbers in correct sequence. (A3113 would come before A4, because 0.3113 is smaller than 0.4.)
Example: HV 1431 .B7 before HV 1431 .B83 before HV 1431 .F25 before HV 1431 .F7
Editions are often arranged by date or by the date and letters.
Example: PS 3525 .I52 1971 before PS 3525 .I52 1973 before PS 3525 .I52 1973a

(Explanation courtesy of SUNY Buffalo Libraries.)