any one help me how to increase the input output port of micro controller..........as let us suppose a micro controller with 30 i/o and we have required more i/o for same micro controller then how it is increase i/o pin of that uc . please help me

 

use multiplexing or shift registers.

if using shift, check 74hx595 and 74hc597. you can cascade them to get any number of inputs and outputs at the expense of clock cycles needed to shift values in and out.

 

If your microcontroller has I2C interface, you can use I2C I/O expander ICs.

 

Texas Instruments and many other companies make serially interfaced I/O expanders. Go to digikey and search for "I/O expander". They have a whole category for these, with over a thousand part numbers.