The Aim of this book is to deal with advanced Microprocessors and Microcontroller, their programming and interfacing etc. It includes architectures of Intel 80286, 80386, 80486 and Pentium 80586 microprocessor and 8051 Microcontroller. This book is very useful to B.C.A., M.C.A., M.Sc. Electronics, M.Sc. Computer Science, Diploma in Electronics and Computer Science and Engineering in Electronics and Computer technology students.The Material has been presented in a very simple and logical manner using step-by-step development of the subject matter. Clarity and the practicability are the keynotes of the text which has been written with shorter sentences, shorter paragraphs and more subheads. Successful efforts have been made to provide very concise and clear explanations of these circuits and devices which most of the students find difficult to comprehend. As will be found by the readers themselves, all these have been presented in a manner which apart from being easy to understand is refreshing originally. All along, author’s intention has been to express, not to impress.