It's Deep Thought, the second greatest computer in time and space, built for the sole purpose of figuring out the answer to The Ultimate Question Of Life, The Universe, And Everything.
It was so amazingly intelligent that before its data banks had been connected up, it started from first principles like "I think, therefore I am" and had correctly deduced the existence of rice pudding and income tax before anyone could shut it off.
--Douglas Adams, Hitchhiker's Guide, Fit the Fourth
Finally, seven and a half million years after the initial program was put into motion the computer announced that the answer to The Ultimate Question was 42. Deep Thought made it clear that a second computer had to be built in order to find out what the Question really was. This computer was so massive that it was very often mistaken for a planet (especially by the ape-descended life forms covering its surface) and was called "The Earth." However, at the critical moment of readout, the earth was unexpectedly demolished to make way for a hyperspace bypass.
-- Douglas Adams, Hitchhiker's Guide, Fit the Fifth