Cows&Bulls

I think of a word consisting of four characters. None of characters are repeating in my word. Your task is to guess my word. You can make a word guess which , again, consists of 4 characters with none of the characters repeating. For every character in your word which occurs at the same position in my word, I count a Bull. And for every character which of your word which is present in my word but not in the same position I count a Cow. I will tell you the number of Cows and Bulls for your guess.You can guess as many times as you want. But I will keep track of the number of guesses you made.