It's not very good style, and probably not necessary, but it converts anything besides 0 to 1, just in case digitalWrite() only accepted 1 for HIGH. That is, !!5 is 1, and !!0 is 0.
It's not very good style, and probably not necessary, but it converts anything besides 0 to 1, just in case digitalWrite() only accepted 1 for HIGH. That is, !!5 is 1, and !!0 is 0.