The subject of Microprocessors is being taught in universities since last 40 to 45 years. During these years, technology has evolved at fast pace and hundreds of processors became commercially available. Students have a challenge to keep abreast of the advanced architectures continuously. But new architectures can be learnt only when their basic concepts are strong. The objective of this book is to expose the students having little knowledge of digital electronics up to the level of current processor architectures with a step wise approach. This book is the result of my course content of Microprocessors which got continuously updated since 1983. Hundreds of books are available on this subject. Each one focusses on a single or family of microprocessors, its instructions and how to develop applications around it. This book is authored with little different approach. It discusses basics of realizing processors from digital hardware then to primitive processors and then the necessity of architectural advances. Concepts behind advanced processor architectures are covered so that students can comfortably understand and work with modern processors. In summary, a student can confidently understand internals of complex microprocessors and develop complex systems after going through the chapters and solving the exercises in each chapter. The exercises are designed from open book tests. One has to thoroughly understand the subject to solve the problems.