Minecraft wiki entry for Logic_gates, associated text: We could repeat this forever, but that would be useless. This is about what a 4 bit register does: it truncates after 4 bits worth of data. So after we truncate the number (which I kindly did for you in the example, otherwise the number would have an infinite number of 1's to the left). Thanks to this little perk, we can do whatever we want to the 0's after the four of them, including (which will prove to be fantastically useful later) adding a single 1 in front of them.