The ALA, the Canadian Library Association and the Chartered Institute of Library Information Professionals (U.K.) publish the AACR2, which contains cataloguing rules that were developed for bibliographic data over a long period of time. AACR cataloguing rules dictate where the library material belongs in the library catalogue, which is now generally online, and where it rests on the shelf, identifiable by call numbers on a label on the library material . The AARC2 rules are very complex and difficult but dictate shelving to some extent. Getting the books back on the shelves is essential. Shelving rules expedite the shelving.
The Dewey Decimal Classification System, devised by Melvil Dewy in 1870, is used in school libraries, public libraries and small college libraries. It is a logical, familiar system used widely around the world in over 200,000 libraries. Students learn the system easily and it is not difficult to teach because it has 10 main identifiable classifications. Tutorials and presentation materials are widely available. When these library materials are returned, shelving is relatively easy.
The Library of Congress devised its own system for classifying books and other library material. The alphabet and numbers are used to divide human knowledge into categories. These are indicated by English alphabet categories. LLC is used in universities and research libraries. This system, originally developed by Herbert Putnam, replaced Thomas Jefferson's fixed location system. LLC is not a classification of the world, but information on where the book is in the library. There is lots of room to expand in this system and because the system uses decimals, a subject can be defined infinitely. Library materials are shelved for maximum access, but you may need a librarian to help you at first. There are tutorials to help you learn this system
Government documents have their own world and are catalogued using the Superintendent of Documents System. It was developed in the Library of the Government Printing Office between 1895 and 1903 and classifies documents by governmental author. An example of a SuDoc system holding is "U.S. Army Medical Department Journal" call number : D 101 .42/3: Holdings: 1996-, Department: Army Department. Government documents using the SuDocs system are not found in every library. They reside in Federal Government Depository Program libraries.
Libraries generally shelve different types of materials together. Reference books, which can not be checked out, are usually together in an identifiable section. The general collection contains Fiction and Nonfiction. Fiction is shelved together and Nonfiction the same. The reserves section is where a professor might put documents, old tests and other material. The borrower can only keep it for a short time, enabling other students a chance to see it. There may be a print periodicals section even if the library has the newest journals online. Librarians learn all of the above shelving rules in ALA-approved library schools.