Cows and PiGGs

Cows and PiGGs is number guessing game where computer generates a 4 digit number and user gets 10 chances to guess it. Each time when user guess the number Computer will provide hints in terms of Cows and PiGGs. Where 1 Cows means that 1 digit is correct but position of that digit is incorrect. 1 Bull means that 1 digit is correct and it is in correct position as well.