This book is an introduction to the Prolog language for those who have not yet used Prolog and want to find out how it works and also for those considering using it in a specific application. The book assumes no prior knowledge of Prolog and very little knowledge of other computer languages. The authors have deliberately produced a short text in order to give the reader a good feeling for the language. The book is divided into two parts. Part One, Prolog Programming, explains the basic concepts incorporated into almost all implementations of Prolog. Part Two, Projects, demonstrates examples and areas in which Prolog shows itself in the best light. A chapter on operators is used to enable a meta level expert system to be developed.