Binary Arithmetic

A processor cannot do arithmetic the way you were taught it at primary school, because it has no digits from 2 to 9 to work with. It has 0 and 1, and out of those two symbols and one rule about carrying it builds every sum, every difference, every price total and every frame of every game you have ever played. The surprising part is how small that rule is: binary addition has four cases, and you already know three of them.

This lesson teaches you to add two binary numbers by hand and to shift a binary number left or right, which is the trick a processor uses to multiply and divide by powers of two at almost no cost. You will also learn what gets thrown away when a shift runs off the end of an eight bit register, because knowing what a shift destroys is what separates a candidate who can perform one from a candidate who can be trusted to use one.