Moo

Moo is an implementation of the pen and paper game Bulls and Cows (later commercially popularized as Mastermind). It ran on the Titan computer at Cambridge University. The player must guess a code of four numbers randomly picked by the computer. The player enters a code and receives an amount of bulls and cows in return. Bulls being numbers in the correct spot and cows being numbers in the code, but in a different spot. It's up to the player to deduce the code in the fewest possible steps.