What are Microcontrollers?

A controller is used to control some process whereas a microcontroller is a complete computer system at its level. A microcontroller is a highly integrated chip which includes, on one chip, all or most of the parts needed for a controller. The microcontroller could be called a "one-chip solution".

It typically includes:
CPU (central processing unit)
RAM (Random Access Memory)
EPROM/PROM/ROM (Erasable Programmable Read Only Memory)
I/O (input/output) and
- serial and parallel timers interrupt controller.

But all these things are very limited and we have to care for the efficient use of these resources. Cost of a microcontroller is relatively low. Microcontroller is designed for a very specific task -- to control a particular system. As a result, the parts can be simplified and reduced, which cuts down on production costs. Microcontrollers are sometimes called embedded microcontrollers, which just means that they are part of an embeded system-- that is, one part of a larger device or system.

A microcontroller differs from a microprocessor, which is a general-purpose chip that is used to create a multi-function computer or device and requires multiple chips to handle various tasks. A microcontroller is meant to be more self-contained and independent, and functions as a tiny, dedicated computer.
Microcontrollers have become common in many areas, and can be found in home appliances, computer equipment, and instrumentation. They are often used in automobiles, and have many industrial uses as well, and have become a central part of industrial robotics. Because they are usually used to control a single process and execute simple instructions, microcontrollers do not require significant processing power.

Microcontrollers comes in different size and different types. They are made my a number of companies. They come in basically two packages;

DIP and QUAD

in DIP package despite from the other differences; the pins are at two sides and in quad the pins are at four sides. you can see them in below image.



Today MCUs are hidden inside a surprising number of products these days, if your microwave oven has an LED or LCD screen and a keypad, it contains a MCU. All modern automobiles contain at least one MCU, and can have as many as six or seven: the engine is controlled by a MCU, as are the anti-lock brakes, the cruise control and so on. Any device that has a remote control almost certainly contains a MCU: TVs, VCRs and high-end stereo systems all fall into this category. Nice SLR and digital cameras, cell phones, camcorders, answering machines, laser printers, telephones (the ones with caller ID, 20-number memory, etc.), pagers, and feature-laden refrigerators, dishwashers, washers and dryers (the ones with displays and keypads) and product or device that interacts with its user has a MCU buried inside.

You can also read about MCUs from these links;

http://www.seattlerobotics.org/encoder/sep97/basics.html
http://knowledgerush.com/kr/encyclopedia/Microcontroller/
http://cnx.org/content/m11655/latest/