Question

design a combinational circuit the generates the 9's complement of a bcd digit

Answer 1

I once made a real-time multi-camera video processing software, doing motion detection and cumulative histographic magic, all on 33MHz processors and 640Mb of RAM. The hard part was making this go fast; copious amounts of hashing, bits-shifting, cheating, swearing and late nights with pizza and ephiphanies for about 4 years. Oh, and I did a version dealing with color as well. Oh, and a module that could see the difference between steam and white smoke in large rooms (like nuclear reactors, as it were). Hah, you just try it! You wouldn't find examples of such in any text-book. :)