This post is part of a series in which I am following the structure of J. Clark Scott’s book But How Do It Know? (Affiliate Link – commission supports my knowledge quest). You can check out his website at http://www.buthowdoitknow.com/ (not an affiliate link). It’s written with no assumption of knowledge or background in computers, which has been great for me ðŸ˜‰

## How Does an Adder Work?

As its name suggests, an adder takes two binary values and adds them together. My first thought was “that’s cool but how do you make it 32 or 64 bit?” which is a reasonable question. We’ll get to that, and it’s fairly straightforward. But understanding the simple (half) adder is key to understanding how the more complex ones work.

So if A = 1 and B = 1, this contraption using an XOR and AND gate will add them together to get O (output) = 0 and C (carry) = 1. Binary 10, aka 2. 1 + 1 = 2 right? You’ll find if you change out other values for A and B they’ll come out correct.

This also serves to illustrate that there are 10 kinds of people in the world, those who understand binary and those who don’t! Haha! ………ahem.