Spoilers below (for the book, not the movie).
- A robot may not injure a human being, or, through inaction, allow a human being to come to harm.
- A robot must obey the orders given it by human beings except where such orders would conflict with the First Law.
- A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.
Obviously we have no idea how to program a computer with laws like this, but that's OK because what the robot stories is really about is the Law of Unintended consequences, a familiar concept to computer programmers. The three laws sound simple but in each one of the stories, Asimov finds some situation in which the laws drive the robot into seemingly insane behavior, and the humans around it (and the reader) need to figure out what's going on and how to unwedge it--a familiar experience when dealing with computers.
In probably the simplest one, "Runaround", a human gives a robot (Speedy) a casual order to perform a task in a mildly corrosive environment. (They're on Mercury and the robot is told to fetch some selenium from a pool, but it's not important to understand the basic idea). Speedy is a particularly expensive model and so the Third law has been strengthened. Because the order was relatively weak, there's an eqiulibrium point where the potentials cancel out and the robot just circles the danger area endlessly, and the humans in the story need to work out a way to break the deadlock, which they eventually do--mostly by accident--by engaging the First Law.
Definitely worth checking out.
