Library of Congress Classification System

The majority of Tomlinson Library materials are indexed according to the Library of Congress (LC) Classification System. Think of the LC call number as the book or other item's unique address, found on a sticker attached to the materials you will find on the library's shelves.

LC call numbers begin with either one or two letters which stand for a broad subject grouping; subsequent numbers and letters serve to narrow down the subject. No two books have exactly the same call number.

A typical call number looks like this:

PS
539
.W193
H6
1986

An LC call number can also be displayed like this:

PS 539 .W193 H6 1986 or PS539 W193H6 1986

The first line is read alphabetically. All of the following examples are in proper order:

The next line is read numerically:

The number part of the third line is actually a DECIMAL number (called a Cutter number), not a whole number like the second line. Therefore, .D59 comes before .D6. The decimal point appears before the letter on that line:

Line four is called the Double Cutter number. It too is treated as a decimal number even though there is no decimal point showing:

Also remember:

• "Nothing comes before something": R 469 .M13 B3 goes on the shelf before R 469 .M13 B3 1993
• Single letters come before double letters in alphabetical order. Call numbers beginning with LA come AFTER those beginning with L and BEFORE those beginning with LB.
• The number directly after the letter(s) is always a whole number that occasionally has a decimal. Don't confuse it with the Cutter number.
• In the Tomlinson Library, Reference books are labeled with a "Ref" appearing before the LC call number.