If an input pin is not connected to anything, it is said to be floating.
This means that, if you read it, you can't be sure what it will return - maybe HIGH, maybe LOW.
If the pin is an interrupt, you may get spurious interrupts.
Connecting the pin to either the supply rail or the ground via a resistor means that if you disconnect the pin, you can be sure it will consistently read high (supply) or low (ground).
The AVR provides pullup (connected to supply) internally, or you can use external resistors for pullup or pulldown.
The internal pullups are enabled by performing a "digitalWrite (myPin, HIGH);" on a pin configured as an input.
have u seen the picture that i have attached....i connected all the wires accordingly....can u plz refer with this
Can you start using English please?