Dear Amit,

One way is to use the 8 channel switch debouncers from Maxim as Jez has suggested. they can generate an interrupt and save the trouble of polling.

But if you have a larger number of inputs then go by the standarad route - keep getting snap shots of the inputs and compare them with the previous snap shot at intervals that you can afford . And if you can't afford anything less than 20ms or so then you HAVE to look for better methods. Actually if you are talking about control buttons that have a user interface then even 100mS is fast enough. ( Can you press a switch 10 times in a second ? If you say yes - well ...)

Raghu