Thanks! I understand better now.

And that cheat sheet PDF is cool, exactly what I was looking for. Any chance you are aware of something similar for x64? Thanks.

No, sorry. Honestly I spent a long time going to the source of the 3-volume Intel manual. (There's link to them as well in my Readme.) I think that's really what you need to do for machine code, if you're not using Assembly or Assembly-ish that has done that work for you. But then any Assembly language will have its own manual you need to bone up on.. That's mostly why I built SubX: the manual is like 10 pages, and I distilled down the parts of the Intel manual you need to know. But yeah, only for 32-bit. I always found x64 very hacky with the register bits split up between bytes and whatnot. 32-bit is a legitimately nice ergonomic machine.

Thanks for your efforts creating SubX. Now I understand the motivations behind that better.