This book has been written to have a knowledge regarding Microcontroller based GSM/GPRS projects. A Microcontroller is a single-chip computer. Before the invention of the Microcontrollers most intelligent systems were premeditated using microprocessors. A microprocessor is the processing component of a computer, comprising of an Arithmetic and Logic Unit (ALU) and the Control Unit (CU). A microprocessor on its own has no use and it has to be sustained by a large number of peripheral chips, such as memory, input-output device, timer, counter, interrupt logic and so on. Currently there are many Microcontroller chips manufactured by numerous companies. This book demonstrates the basic principles of Microcontrollers and shows how they can be used in GSM/GPRS based communications projects.