A robot should not injure a human and it should not standby and watch a human in danger either.
In case the principle 1 is not violated, a robot should obey a human's orders.
In case the principle 1 and 2 are not violated, a robot should protect itself.
The word, robot, was first used in the play R.U.R(Rosuum's Universial Robots) by Karel Capek, a Czech play writer in 1921. The origin of the word, robot, is allegedly known as coming from the Czech word ‘robota' meaning labor.