Three parrots

A man goes into a pet shop to buy a parrot. The shop owner points to three identical looking parrots on a perch and says: "The parrot on the left costs 500 dollars."

"Why does the parrot cost so much?" asks the man. The owner says, "Well, the parrot knows how to use a computer."

The man then asks about the next parrot and is told that this one costs 1,000 dollars because it can do everything the other parrot can do plus it knows how to use the UNIX operating system. The increasingly startled man asks about the third parrot, to be told that it costs 2,000 dollars. So he asks, "And what can this one do?"

To which the owner replies, "To be honest I have never seen it do a damn thing, but the other two call him 'boss'!"

-- from that great joke factory in the sky