The Library of Congress Classification Scheme

Books and videos are arranged on the library's shelves according to the Library of Congress (LC) classification system. Using this system, each book or video is assigned an alphanumeric call number based on its subject focus. This call number uniquely identifies the item and places it on our shelves near other material on the same subject.

Each call number consists of several parts. For example, consider the call number:

PR 5318
.A1
1986

The FIRST line, PR, defines the class and subclass. These letters specify a broad subject area. Within Class P for general linguistics, PR represents the subclass English Literature.

The SECOND line, 5318, is the classification number. It should be read as a whole number with a decimal component (if there is a decimal component) to determine its location on the shelf. In combination with the class and subclass, the classification number defines the subject matter more finely. In this example, PR 5318 represents English Literature (the English Literature does not have any refined subject classifications).

The THIRD line, .A1, is called a "Cutter Number." This letter-number combination usually indicates author, but it may also represent other information such as further subject subdivision or geographic area. The Cutter number is always present in a call number and may sometimes be a "double Cutter" (HF5548.4.M525 C86 1997 has a double Cutter). The numeric component of the Cutter number is ALWAYS interpreted as a decimal number when determining shelf location. Therefore, the numeric component of .M25 should be read as ".25" (and the call number HF5548.4.M525 C86 1997 should file BEFORE HF5548.4.M60 C86 1997).

The YEAR of publication, 1986, may also be present. Not all call numbers will include the year of publication, but most recent books will. These file in chronological order and often distinguish among varying editions of a text.

There are other miscellaneous descriptors that may be part of the call number. If present, these will usually differentiate the components of a work that has one title but was published as separate volumes or in parts over time.

In using a call number to locate a book on the shelf, consider each component of the call number in turn before moving on to the next segment. As an example, the following call numbers are arranged in the order they should appear on the shelves:

QA
76
F75
v.1

QA
76
F75
v.2

QA
76
F8
v.1

T
3
Z37

T
39
W45
M226
1989

T
39
W45
M26
1989

TA
3
Z3

TK
7881
L444
1994
v.2

TK
7881.15
D2
1988

TK
7881.15
D2
1995

TK
7881.6
M29
1993

To find more specific subjects, search the classic catalog using Keywords as your search type. Then, identify the call numbers for relevant books from your search and browse for other books near these call numbers.

If you have difficulty locating items on the shelves or have other questions about call numbers, please ask at the Reference Desk.