I've taken classes in Basic, C++, Java, other languages. I've read "exceptional" and "effective" and other books to improve my craft over the years.
But building from the ground up in an introduction to digital logic class way back in 1978 still had the most profound impact on my ability to know what's happening in a computer and on my ability to understand what's really going on "under the hood", even 35 years later.
It literally started with diodes and transistors. Building 'and' and 'or' and 'nor' (and...) gates. Hooking them together to make a flip flop. Then taking pre-built gates and making a counter. On to a simple cpu (that only knew a couple of 'instructions', IIRC). When I built an 8080 based computer, I actually knew how it worked. There has always been something comforting knowing that, deep down inside even the most powerful processors, it's still just a bunch (ok, a WHOLE LOT) of gates.
Unless this whole quantum thing gets properly defined and implemented and catches on. Maybe I'll get to start over.