Many academic libraries in the United States use the Library of Congress Classification for call numbers. This system uses a combination of letters and numbers to arrange materials by subject on the shelves ("the stacks") of a library.
The LCC System is preferred for academic collections because the call number, being alphanumeric, can be shorter and more descriptive than by using numeric systems like Dewey Decimal, used by public libraries.
Each book in the library has a unique call number. A call number is like an address, it indicates where the book is shelved in the library.
The same call number can be written from top-to-bottom, or left-to-right. The number generally gathers together books on similar topics, then grouped alphbetically by author and year.
However, even though LCC groups books on similar subjects together, it is important when doing research to always check the online catalog rather than merely browsing the shelves, because books on a topic might be located in several places in the library, depending on their emphasis.
Call numbers are read line by line. First comes a letter or a two letter combination.
The first section of the call number represents the subject of the book.
The letter-and-decimal section of the call number often represents the author's last name, but sometimes it also represents a subject that is narrower than the broad classification number (the classification system defines the rules for how each subject area is treated so there is consistency).
The last section of a call number is often the date of publication. The date make it easy for a researcher to evaluate the currency ("the up-to-datedness") of the book before pulling it off the shelf.
