State the library classification system.

The library classification system is a system used by libraries to organize and categorize books and other materials in their collections. The most widely used library classification system is the Dewey Decimal Classification system, which categorizes materials into 10 main classes based on subject matter. Each main class is further divided into subclasses, with each subclass assigned a unique number. Other library classification systems include the Library of Congress Classification system and the Universal Decimal Classification system.