Library of Congress Classification System
Index
Understanding Call Numbers
A sample call number:
QE 534.2 B64
Call numbers begin with one, two, or, three letters
The first letter of a call number represents one of the 21 major divisions of the LC System. In this example, "Q" stands for Science.
The second letter "E" represents a subdivision of the sciences, Geology. All books in the QE's are primarily about Geology.
Books in categories E, United States History, and F, Local U.S. History and American History, do not have a second letter.
Books about Law, K's, can have three letters, such as KFH, Law of Hawaii.
All other subject areas will have call numbers beginning with one or two letters.
For most of the subject areas, the single letter represents books of a general nature for that subject area (i.e. Q - General Science or D - General World History).
Numbers after letters
The first set of numbers in a call number help to define a book's subject.
"534.2" in the example teaches us more about the book's subject. The range QE 500-625 are books about "Dynamic and Structural Geology."
Books with call numbers QE534.2 are specifically "Earthquakes, Seismology - General Works - 1970 to Present"
One of the most frequently used number in call numbers is "1" which is often used for general periodicals in a given subject area.
For example, Q 1 S3 is the call number for the journal Science
Journals are also given call numbers based on the specific subject.
For example, QE 531 E32 is the call number for the journal Earthquake Spectra as QE 531 is the call number for periodicals about "Earthquakes, Seismology"
The cutter number
The cutter number is a coded representation of the author or organization's name or the title of the work, also known as the "Main Entry. The "S3" in our last example is simply code for the journal title Science.
QD 1 A5 is the call number for the Journal of the American Chemical Society. The A5 represents the name of the author, in this case the American Chemical Society.
What can we determine from the book QE 534.2 B64? First, the Q indicates Science and the QE indicates Geology. By looking at the first numbers, 534.2, we know this falls under the subcategory under geology of "Dynamic and Structural Geology, Earthquakes and Volcanoes". And the Cutter Number? The Cutter Number of "B64" tells us that the book was written by Bruce A. Bolt and is none other than the book Earthquakes. The call number tells a lot about an item.Shelving and Locating
Items are shelved by call numbers - in both alphabetical and numerical order. The letters at the beginning of the call number are alphabetical. The numbers immediately following are in ascending numerical order.
QD 1 A3 QD 2 A 31 QD 3 Z 4 QD 29 C 3 QD 30 A 2 The cutter numbers (A3, A31, Z4, C3, and A2 in the above example) are sorted first by the letter and then by the number as a decimal. For QD 1 A5, think of it as being QD 1 A 0.5, for QD 1 A332 read QD 1 A 0.332. Therefore,
QD 1 A3 QD 1 A 31 QD 1 A 311 QD 1 A 4 QD 1 A 405 QD 1 A 41 QD 1 A 4105 Dates, volume and issue numbers, copy numbers, and other annotations are like an additional cutter number but are shelved by basic alphabetization (numbers alone come before letters):
Q 10
C 3Q 10
C 3
1933Q 10
C 3
1990Q 10
C 3
1996
copy 1Q 10
C 3
1996
copy 2QD 1
A 5
Vol. 1QD 1
A 5
Vol. 2QD 1
A 5
Vol. 2
PlatesQD 1
A 5
Vol. 2
Supplement