The 8051 is at the core of many modern 8-bit microcontroller systems. This book provides a comprehensive introduction to embedded systems concepts, with the 8051 as its centrepiece. It starts by explaining the basics of all microcontrollers, then examines 8051 specifics, including the timers, the serial port, interrupts and peripheral interfacing. Screenshots of the EdSim51 simulator (freely available from www.edsim51.com) are used throughout the text to show the microcontroller in action. The simulator is an ideal companion to this book as it will aid the student gain a clear understanding of embedded systems in general and of the 8051 in particular. The book contains many example programs, written in assembly. Finally, the reader is introduced to C programming for the 8051.