Q.What is a microcontroller?

A microprocessor is a general-purpose Central Processing Unit built on a single chip. It performs the processing, but on its own it is not a complete computer: a designer must connect external RAM, ROM, I/O ports and a timer before it can do useful work. Because of this it is optimised for the rapid movement of code and data between external memory and the chip, and it is meant to be a flexible, general-purpose engine.

A microcontroller is a "computer on a chip". It contains everything a microprocessor has and, in addition, on-chip ROM, RAM, parallel and serial I/O, timers/counters, and interrupt and clock circuits. Nothing extra has to be bolted on, so a single chip can run a whole dedicated application. It is optimised for the rapid movement and testing of individual bits inside the chip, and is a special-purpose controller rather than a general computer.

The key differences a Karnataka 2nd PUC Electronics student should remember: the microcontroller has memory and I/O built in while the microprocessor needs them added externally; the microcontroller offers many bit-handling instructions while the microprocessor offers few; and the microcontroller targets control tasks (washing machines, microwave ovens, toys) while the microprocessor targets general computing. This trade-off — less raw computing power, but low cost, tiny size and very low power — is exactly what makes microcontrollers ideal for embedded control.