How to... Understand Call Numbers and LC Classification

Books and scores in the Palm Beach Atlantic University Library are organized on the shelves according to Library of Congress (LC) Classification. LC Classification was originally designed to sort books at the Library of Congress and developed specifically with reference to the published literature in each subject area in that collection. Today it is used widely to organize collections in American academic and research libraries.

The basic outline of LC classification divides the entire field of knowledge into main classes that correspond largely to academic disciplines or areas of study. Main classes are denoted by single capital letters:

The main classes are in turn divided into subclasses, designated by double or triple capital letters, representing branches of the major disciplines. The outline of the individual classes have been developed separately for each subject area—Class M, Music, for example, was first published in 1902 and was largely the work of Oscar G. Sonneck, Chief of the Division of Music at the Library of Congress. Nevertheless, the various classes are unified by a number of principles, most notably in the patterned structure of the notation, or call numbers, used to identify each class and the individual items within each class.

Elements of a Call Number. Each book or score in the Music Library is uniquely identified by a set of letters and numerals known as a call number. Call numbers generally consist of two or three elements: an LC class number followed by a tag known as the Cutter number (or book number) and often a date.

The class number begins with one or more capital letters representing a branch of a subject classification in LC, the broad neighborhood of items related by subject, discussed above. Within each main class or subclass, the integers 1-9999 (some with decimal extensions) are added to identify further subject subdivisions, defining the subject matter of the item more finely. The same combination of letter(s) and numerals is given to all individual items in the same subject class area.

After the first combination of letter(s) and numerals identifying the subject class another combination follows, known as the Cutter number. Named after Charles A. Cutter, who developed an alphanumeric code that forms the basis of the number, this second letter/number combination places an individual item in alphabetical order within its LC subject class (usually by the first letter of an author's last name, though it may sometimes also represent some other information about a work such as a further subject subdivision). In order to assure the Cutter number is unique a date often follows. Thus, the two parts of the call number serve two very different functions: the first part (class number) organizes knowledge by subject and the second part (Cutter number[s] + date) acts as a shelving device for arranging individual items within subject classes.

For example, the following item from the PBA Library:

Arnold, Denis. Bach. (Oxford; New York: Oxford University Press, 1984).

has been assigned the call number ML410.B1A96 1984, where ML410 is the LC class number and .B1 .A96 are the Cutter numbers.

The meaning of the LC call number can be analyzed part by part:

ML410 is the classification for composer biographies: ML represents Music Literature, a subclass of class M Music. The number 410, which is added to ML, represents Biography (by composer last name), itself a subdivision of the group of numbers representing History and Criticism under Music Literature.

The remainder of the notation, .B1 .A96 1984, is added to the class number in order to distinguish the specific item by Denis Arnold from all other items within the class of items at ML410. In this case, .B1 .A96 is a "double cutter," where .B1 may be seen to form part of the class number, or an extension of it, because it is a subdivision of Biography referring to books on J.S. Bach. Since all biographies of J.S. Bach are given the number ML410.B1, a second Cutter, .A96, is added to refer specifically to Arnold’s biography of Bach. Together, the class number and the book number form a unique call number—an address that communicates information about the subject of an item and where a specific item may be found within (an alphabetical list of similar items in) its subject class.

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. Each element of the call number is read is a different manner—the class letters alphabetically, the class number as a whole number (with possible decimal extension), and the Cutter as a decimal. For example, the following call numbers are in the order they should appear on the shelves:

Implications for Research: Browsing the Shelves. Since books on similar subjects are kept together by class number you can use the Library of Congress Classification, the first part of the call number, to browse the library shelves for information in your area of interest. Looking for books in the same or nearby class number can turn up related material in a particular subject. When looking for specific materials (a certain author or title, for example) you should use the PBA Library online catalog to locate the exact call number of the item, and to check its status. However, if you would like to see what the Library has available in a particular subject area you may simply want to browse the shelves, either in the reference or the circulating collection. An online version of the summary tables for the three classes devoted to music—M Music, ML Literature on Music, and MT Musical Instruction and Study—is available from the UC Berkeley Music Library. An online subject index to the LC Music Class is available from Indiana University Music Library. If you have any questions interpreting a call number or locating an item or area please don't hesitate to ask at the main library desk.

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