This book is about the structure and function of computers. Its purpose is to present, as clearly and completely as possible, the nature and characteristic of modern-day computer systems. This task is challenging for several rasons. Firs, there is a tremendous variety of products that can rightly claim the name of computer, from single-chip micropsocessors costing a few dollars to sepercomputers costing tens of millions of dollars. Variety is exhibited not only in cost, but also in size, performance, and application. Second, the rapid pace of changes used to construct computer components, to the increasing use parallel organization concepts in combining those components. In spite of the variety and pace of change in the computer field, certain fundamental concepts apply consistently throughout. The application of these concepts depends on the current state of the technology and the price/performance objetives of the designer. The intent of this book is to provide a thorough discussion of the fundamentals of computer organization and architecture and to relate these to contemporary design issues.