A microcontroller (or MCU) is a computer-on-a-chip used to control electronic devices. It is a type of microprocessor emphasizing self-sufficiency and cost-effectiveness, in contrast to a general-purpose microprocessor (the kind used in a PC). A typical microcontroller contains all the memory and interfaces needed for a simple application, whereas a general purpose microprocessor requires additional chips to provide these functions. A microcontroller is a single integrated circuit, commonly with the following features: -central processing unit - ranging from small and simple 4-bit processors to sophisticated 32- or 64-bit processors -input/output interfaces such as serial ports -peripherals such as timers and watchdog circuits and signal conversion circuits. -RAM for data storage -ROM, EPROM, EEPROM or Flash memory for program storage -clock generator - often an oscillator for a quartz timing crystal, resonator or RC circuit.