If you have ever visited a library and browsed its shelf racks for a book to read, you may well have noticed a sticker on the spine of each book with a set of letters and numbers written on it. This alpha-numeric code is part of a cataloguing and referencing system, known as the Dewey Decimal Classification, and is sometimes referred to as the Dewey Decimal System.

The DDC method of classifying and keeping track of books in a library has been in use since the late 1800s. The method, however, has not remained static, but has evolved through the years as technology, and ways of classifying new genres of literature (such as Modernism and Post-Modernism) have come along. In the area of non-fiction books, computing sciences and other new developments have also made it necessary to revise this system.

As you can see, although it is believed by a good many people that the DDC system is only used for academic or non-fiction books, it is in fact used to help classify all books, and is an extremely useful method of ensuring that books are stored on shelves in such a way as to make them easy to locate, and to return to their correct position.

The reason it is known as a decimal system is that books are placed into ten classes to begin with. These classes are then divided down into ten subclasses. Since its advent in the 19th century, the Dewey Decimal Classification system has had 22 major restructurings.