This book is about computer architecture, which is one of the most important subject in understanding the fundamental concepts behind design and development of today's computer systems. Instruction set design, parallel processing, parallelism at the bit, instruction, and data levels, distributed computing, virtualization architecture are all topics covered in this book. Description about advanced design principles of modern processor by addressing basic concepts like instruction set design, architecture of superscalar processors and their interactions with other hardware modules. This book also included the concepts of different performance measure and the techniques for reducing power dissipation of computer systems. The concepts of efficient memory design as well as design constrained are included. Any application that is running on computer system like web surfing, sending email, programming, writing documents are directly influenced by the underlying architecture of computer system. The understanding of underlying architecture of computer system helps users to design, develop and implement applications in better, faster, cheaper and in efficient way.