Simply the call number is the address of a book on the shelf. Most academic and research libraries use a system abbreviated as the LC (Library of Congress) system to address books. The Library of Congress classification system organizes books and other library materials by subject, to make it easier for you to browse the shelves for materials on a specific topic. Library of Congress call numbers always begin with letters of the alphabet. The letters identify the subject of the work.

In the LC system, the first letter of the call number indicates the general subject area. The second letter indicates the specific sub-section within the general subject category. In the example given below, the first D in the call number indicates that the book is a work of history. The second D indicates that it is a work of German history.

In the following outline of the Library of Congress classification system, the major classes--indicated by a single letter-- are subdivided into narrower categories, indicated by a double letter.

In the J. Conrad Dunagan Library at the University of Texas of the Permian Basin; reference materials, periodicals and newspapers, and a selection of leisure reading titles are found on the first floor. The second floor houses the primary collection of circulating materials (books that can be checked out) from the library.