A microcontroller is a single-chip computer. Before the invention of the microcontrollers most intelligent systems were designed using microprocessors. A microprocessor is the processing element of a computer, consisting of an Arithmetic and Logic Unit (ALU) and the Control Unit (CU). A microprocessor on its own is useless and it has to be supported by a large number of peripheral chips, such as memory, input-output, timer, interrupt logic and so on. Currently there are many microcontroller chips manufactured by various companies. This book is based on using the highly popular PIn6F887 type microcontroller. GSM/GPRS modems are used in all mobile phones. This book teaches the basic principles of microcontrollers and shows how they can be used in GSM/GPRS based communications projects. All of the examples and the projects in the book are based on the highly popular mikroC language, developed by mikroElektronika.