The problem with hardware is it
doesn't behave nicely. In the case of switches they don't just turn off and on. They bounce. When you push a button
it will go on, then off, then on, then off, before it goes on and stays on. The common way to deal with this is
to read a switch's input
and if it has changed state you must ignore it for a fraction of a second. Just long enough for it to stop bouncing.
Then you may reliably read it as input again.
The problem with hardware is it
doesn't behave nicely. In the case of switches they don't just turn off and on. They bounce. When you push a button
it will go on, then off, then on, then off, before it goes on and stays on. The common way to deal with this is
to read a switch's input