MicrocontrollerMIcrocontroller
A microcontroller is an IC(Integrated circuit) which has its own memory(RAM) and ROM(to store code), I/O ports  and an intelligent unit like microprocessor. Microcontroller executes the sequence of instructions that  you specify in your code.Embedded system is a term most widely used with microcontrollers and microprocessors. Embedded system generally means that the system under consideration is embedded with some intelligent unit. This intelligent unit is infect a microcontroller or a microprocessor. A printer is a good example of embedded system. The microcontroller in side it is programmed to do a single task. That is to get data from user application and print it, or take example of a remote controlled device. The controller inside the device take data from the transmitter decodes it and outputs the Information associated with the received signal.

Microcontroller uses

Microcontrollers are used in many electronic circuits to generate the required output for example in toys,remote controls(Games , Television) .The cell phone which we daily use also contains a micro controller in it. All the peripherals attached to our pc contain microcontrollers in them. Mouse, Keyboard, Printer, Joystick, all Have microcontrollers in side them.

Difference between Microcontroller and Microprocessor

So whats the difference between a microcontroller and a microprocessor.The answer is simple 
  • Microcontroller contains--->microprocessor,Ram,Rom.
  • where as microprocessor is just an intelligent module that is a part of micro controller it self. 
Microprocessors contain no RAM (Random access memory), no ROM (Read only memory) and I/O ports. One has to include RAM, ROM I/O ports and timers externally to make microprocessor fully functional. The addition of all the stuff RAM, ROM and I/O ports make the microprocessor expensive, but it has one big advantage. You can choose the size of RAM, ROM by yourself.

Difference between Microcontroller's

The controllers differs with each other in many aspects, in their memory(RAM) and ROM(to store code). Some have greater RAM some have less some have greater ROM for storing the code and some have less. Number of I/O(input/output) pins, some have 64 some 32 and some 28 . One more difference is in their pins package. some comes in  80 pin package, some 40 some 16 and even 8. Their are many companies which make microcontrollers. Below are some popular of them.
Click to check out the description and products.
  1.  Atmel (Most popular)(Deals in all kind of microcontrollers).     www.atmel.com
   2.     Intel(The name you probably hear every where ;-)).   www.intel.com
   3.     Actel(Deals in only 8051).  www.actel.com
   4.     Dolphin(8051 version (Breeze,Cyclon,Thunder,wind)) 
   5.    Megawin.
Many companies like Philips , Hitachi and Motorola they make their own special type of microcontrollers for use in their products.Below are three most popular types of microcontroller(click to see details and differences in them).

In the projects section you can find lot of projects related to microcontrollers(8051 series(89c51,89c52),pic 16f877 and Arduino). All these microcontroller projects contains free source codes with full project files(hex code etc) and circuit diagrams. Some projects simulations are also given with them.