> Assembly language is the lowest level of abstraction in computers - the point at which the code is still readable.

For simple enough instruction sets it was not unheard of that people memorized the actual opcodes. In school, at the transition from terminals to micros, a friend of mine walked up to one of the new Commodore 6502 machines and entered a simple program in hex directly into the monitor program. For a while I had the common opcodes for the RCA 1802 memorized, due to working with a project board without an assembler (writing assembly on paper, then hand assembling into opcodes, then keying in the opcodes).

There's no returning to those days and I wouldn't if I could, but I can't help but think that I was lucky to have experienced that for the knowledge and perspective.