This is a comparative treatment of knowledge based program design methodology using Lisp as the implementation language. Examples of the design of various system types are given, along with a critical appraisal of each. It is intended to give practical help. The introduction has a comparative overview of computer-based problem solving strategies. Lisp is introduced as an ideal implementation language. The book goes on to deal with problem definition, practical system development and the use of Lisp in the development process, design methodology centred on KBS, the KB building problem, embedded expert systems, KBS based systems and dedicated AI hardware. This book assumes some previous knowledge of computer programming, although the differences between structured procedural and symbolic languages are discussed.