There are two major call number systems used in the libraries: the Dewey Decimal and Library of Congress classification schemes. The first line of a call number, as it appears on a physical item, is a broad subject classification. The subsequent lines are combinations of letters and numbers that organize items into narrower, related categories.
|Library of Congress
615 Whole number
|573.3 Whole number, followed by decimal
|C518 Alphabetically, then decimals
(may be followed by another letter)
|.W932A Alphabetically, then decimals
|2018 Publication Date, shelves chronologically
|e.g., 573.3 W932A shelves before 573.3 W94A
See How to Read Call Numbers from the University of Berkeley Library for more details about LC call numbers.