Microcontroller and MicroProcessor

Microprocessor is a single chip computing unit , it has ALU , Registers for temporary data storage , address and data pins for accessing external memory ,

Timing and control circuits , Program counter etc etc;

A microcontroller has all that what a microprocessar has , sometimes external memory access pins also ,

Difference is that although microcontroller can have external memory access ,most of the time ,memory is fabricated on same piece of silicon , microcontrollers have on chip Program memory ,and some data RAM is also there , Manufactuting Large data size Static RAM is not cheap ,

thats why initial microcontrollers only have internal RAM size of 128 ,256 byte , now a days more complex applications are coming like USB , DSP, which require large size temporary storage , so now microcontrollers come with internal RAM size in kilo bytes ;

Another difference is that if you want to do Some Input /Output device interface with microprocessor you will need to combine its address lines with status signals of Read /write ; IO /memory , to make a proper IO Port ;

In a microcontroller its pins are ready IO ports , it can directly take input /output from some other device , you can address a single pin of microcontroller and can change the logic level on it, through your program.

Microcontroller and microprocessors applications are different ,

A microcontroller is meant for real time applications , with limited program and data memory , ,

for example there is microcontroller in keyboard of PC , which is detecting a keypress , and communicating this to the Computer ,

A microprocessor is for data intensive applications , where the focus is not much on input /output device interfacing but on fast , processing of huge amount of data ,a microprocessors memory is expandable within limits of its address and data bus size

For example :- The Pentium in CPU of computer is a microprocesssor , you can always increase the RAM of your computer upto a limit , which is where all programs are executed ;