Publisher Summary This chapter provides an overview of the embedded system. An embedded system can be defined as “a system whose principal function is not computational but which is controlled by a computer embedded within it.” In embedded systems the computer is hidden from view, such that the user often doesn't know it's even there. Some example embedded systems discussed in the chapter are domestic refrigerator, a car door mechanism, and the Derbot autonomous guided vehicle. The chapter also describes microprocessors and microcontrollers and illustrates differences between the two. The embedded computer is usually a microcontroller: a microprocessor adapted for embedded control applications. Microcontrollers are designed according to accepted electronic and computer principles and are fundamentally made up of microprocessor core, memory, and peripherals. In addition, microchip offers a wide range of microcontrollers, divided into a number of different families. Each family has similar central architecture and instruction set. The Microchip 12F508 is a good microcontroller to introduce a range of features of microcontrollers in general and of peripheral interface controller (PIC) microcontrollers in particular.