The intended readership for this book is the programmer who has experience of programming, preferably in a high-level language. The overall aim is to give the reader a working knowledge of PDP II and the text- and program-editing facilities available on the PDPLOG system. The book will also be useful for undergraduates taking a course in Artificial Intelligence (AI), and for cognitive psychologists, who will find PDP II a more than adequate language to express theoretical approaches to human cognition. In the commercial world PDP II is a major contender to LISP and PROLOG as the development language for intelligent knowledge-based systems. PDP II will offer the experienced PROLOG programmer easier, though high-level, ways of performing particular tasks that are difficult to conceptualize and write in PROLOG.