Microcontroller

n. (Computers) single integrated circuit that is designed to function as an embedded system (contains a CPU, RAM, ROM, I/O ports and timers)

A microcontroller (or MCU) is a computer-on-a-chip. 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). In addition to all arithmetic and logic elements of a general purpose microprocessor, the microcontroller usually also integrates additional elements such as read-only and read-write memory, and input/output interfaces.
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<processor> A microprocessor on a single integrated circuit intended to operate as an embedded system. As well as a CPU, a microcontroller typically includes small amounts of RAM and PROM and timers and I/O ports.
An example is the Intel 8751.
(1995-04-22)

single purpose processing units designed to execute small control programs, sometimes in real time. The program is frequently stored on the microcontroller in an area of nonvolatile memory.