First Law A robot may not injure a human being or, through inaction, allow a human being to come to harm.
Second Law A robot must obey the orders given it by human beings except where such orders would conflict with the First Law.
Third Law A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.
… and :
Zeroth Law A robot may not harm humanity, or, by inaction, allow humanity to come to harm.