It is a complete textbook for anyone interested in all aspects of the microprocessors and microcontrollers family. This book is based upon Microprocessor 8085, 8086 and Microcontroller 8051. All other related microprocessors and microcontrollers like 80186, 80286, 80386, Pentium-4, ARM and PIC are also discussed. All chapters are described with fundamental objectives. A review of important terms and concepts is also given at the end of each chapter that reinforces the idea and material presented. Each chapter also has questions and problems.