The DDC is built on sound principles that make it ideal as a general knowledge organization tool: meaningful notation in universally recognized Arabic numerals, well- defined categories, well-developed hierarchies, and a rich network of relationships among topics. In the DDC, basic classes are organized by disciplines or fields of study. At the broadest level, the DDC is divided into ten main classes, which together cover the entire world of knowledge. Each main class is further divided into ten divisions, and each division into ten sections. Till now most of the changes involved are only change in Connecting Digit and change in a few Array Isolate Numbers, apart from addition of new facets, extrapolation and interpolation in arrays, and lengthening of chains; these two latter changes do not involve any change in the position of the already existing subjects. The aim of the book is to be amply illustrative and to step by step introduce the concepts and methods.