Artificial intelligence (AI) is a branch of computer and information science. The goal of AI is to create a machine that behaves like an ordinary human being, an improved machine behaviour in tackling complex tasks and to accomplish tasks that if accomplished by humans would be considered a display of intelligence. The field of AI includes studying and developing machines such as robots, automatic pilots for airplanes and space ships, and military weapons. Europeans tend to use the term machine intelligence (MI) instead of the term AI. Artificial Intelligence and Expert System is a book about science of artificial intelligence. This book is designed to help students in learning about some of the current applications and techniques of Artificial Intelligence as an aid to solving problems and accomplishing tasks. This book provides a good general introduction to problems and techniques of Artificial Intelligence. We have tried to explore the various branches of Artificial Intelligence which encompass formal logic, reasoning, knowledge engineering, expert system neural networks and fuzzy logic.