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Western Colorado's Selective University

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:

F R RA S TX
157 328 319 118 729
.E52 .L63 .M613 .G584 .L783
D68 N84 W4 F5 E8
1988 1986 1993 1995 1977

The next line is read numerically:

L L L L L
169 170 170.2 170.25 171
.Y29 .H7 .H7 .H7 .R67
K5 T43 J64 J64 B33

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:

T T T T
128 128 128 128
.K79 .K8 .K8149 .K825
B56 T43 M35 M35

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

B B B B
18 18 18 18
.K8 .K8 .K8 .K8
T398 T43 T5 T51

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.