Bulls and cows (also known as cows and bulls or pigs and bulls) is a code-breaking mind or paper and pencil game for two or more players. The game is played in turns by two opponents who aim to decipher the other's secret code by trial and error.
Bulls and cows predates the commercially marketed board game version, Mastermind and the word-based version predates the hit word game Wordle.[citation needed] A version known as MOO was widely available for early mainframe computers, Unix and Multics systems, among others.