Bulls and Cows

Bulls and Cows is a logic game that may be centuries old. You attempt to guess the number the Android device has chosen with a series of responses to your previous guesses. A kind of numerical Mastermind, the program will tell you which digits in your guess are in the number, and which are in the right spot.
Bulls – number of digits present and in the right spot.
Cow – number of digits present but are NOT in the right spot.