Microcontrollers (MCU) are the brain of an embedded system. These are computer scaled down to a single compact chip for managing a specific operation, and are highly integrated single chips with a processor core, memory, I/O Peripherals, timer/counter, and communication ports contained within. These include a range of products offering digital processing under software control. The most important criteria in selecting a MCU for a particular application is the data bus width expressed in bits. MCUs are available in various data widths ranging from 4 to 64 bits. It is used in a variety of general and special applications, including domestic appliances, handheld devices, servers, automotive, network infrastructure, image processing, and communication. MCUs can support RTOS (Real Time Operating System), but typically not a full blown O/S.