Hello everyone, I just noticed, my IC for numbers greater then 9 to output 1, has 4 variables, why does it have to have 4 variables? couldn't I just use ABC?, because isn't 0000 == 000 and 1001 == 101, isn't 1001 9 and 101 9 also? whats the difference? I think if i just used 3 variables instead of 4 it will make the boolean expression must easier to simplfy! because then i could probably use a k-map to help me out. Here is my orginal implementation of a Boolean expression to output 1 if the number is > 9. http://img282.imageshack.us/img282/482/lastscan45vd.jpg [Broken] Could this be implemented with 3 variables?