Microcontrollers are complete computer systems-on-a-chip which are used to control electronic devices. A typical microcontroller will contain all the memory and interfaces needed to run a simple application. RAM size, ROM size, and ROM type are all key characteristics of a microcontroller. Examples of such types of ROM include Flash, EEPROM, and OTP ROM.

Microcontrollers usually contain a wide variety of peripherals such as Digital I/O's, Analog to Digital Converters, Digital to Analog Converters, timers, counters, PWM's and specialized communication interfaces including I²C, UART, CAN, LIN, SPI, USB, and Ethernet. Microcontroller architectures are based on registers, address busses, or data bus sizes of 4-bit, 8-bit, 16-bit, and 32-bit.