Embedded Systems have become indispensible in today's modern advanced technical world. All embedded systems are built with a microcontroller. This book is intended for teaching the usage and programming of the microcontrollers. The book starts with the basic microprocessor and navigates to the most frequently used microcontroller 8051. Complete attention has been paid to the 8051 right from the architecture, instruction sets, programming model, interfacing with the peripherals, application projects and quiz for testing the learners understanding. After 8051, wareness has been raised on PIC microcontroller in a concise way. Finally, few projects/assignments have been discussed and included as per the requirement of the topic. Reader will be in a comfortable state to do them all. ARM is one of the most famous and high end microcontroller architectures which are growing like anything in the market. So the book will get over with solid discussion on ARM architecture with and without THUMB architecture. As far as we analysed, there is no other microcontroller book in the market which has covered ARM and 8051 in this fashion. Throughout the book, there are practical examples which will surely make the reading a fun and a learning experience. Last but not least, readers can be in touch with the authors for their constructive critics and suggestions through the mail ids, dpk0710yahoo.com and shriramkvgmail.com