A couple of years ago I was in this position. I wanted to know how computers work and stumbled upon this resource. I can highly recommend the exercises given on

A couple of years ago I was in this position. I wanted to know how computers work and stumbled upon this resource. I can highly recommend the exercises given on Github by Xorpd. It really requires no prior knowledge and a lot of the exercises have answers now (still a work in progress though). Next to that it might be convenient to have something like asmdebugger.com next to it. Another book that also really helped working with this was "Code: the Hidden Language of Computer Hard and Software" by Charles Petzold. This explains how computers work from light bulb/transistor level, all the way to the top to the OS, the monitor and the keyboard.