Cow = correct letter, but wrong place.
Bull = correct letter and correct place.
The teacher chooses a word that students need to guess and types it into the first space. From personal experience, 4-6 letter words work best. I normally divide the class into 2 teams. Choose easy mode* or normal mode. The students/teams then take turns to guess the word and it will show them how many cows and/or bulls they got. A cow indicates that one of the letters in their guess is correct, but is in the wrong position. A bull indicates that one of the letters in the guess is correct and also in the correct position. They continue until they have guessed the word and the player/team who guesses the word gets a point.
*Easy mode puts a circle around a "cow" and puts a square around a "bull". This makes it easier, as students know exactly which letters are cows or bulls, not just how many they got.
*Easy mode puts a circle around a "cow" and puts a square around a "bull". This makes it easier, as students know exactly which letters are cows or bulls, not just how many they got.