This document provides an overview of the Dewey Decimal Classification system (DDC) used to organize library collections. It explains that Melvil Dewey created the DDC in 1876 to systematically organize books by assigning each topic a unique number. The DDC uses a hierarchical numbering system with ten main classes that are further divided into more specific numbers. It has been adopted by over 200,000 libraries worldwide as an easy way for patrons to locate materials on their topic of interest based on the classification numbers.