Back when I was kid playing with a C64, it was the DATA section at the end of BASIC programs that blew my mind. If you programmed line 10 wrong with a typo or other syntax sin, then the entire thing would fail. If you had a typo in the DATA section that was (now I know as) Hex, then the program would not fail but glitch, and it was typically with the sound/music of the game. I had no idea what Hex was, but I did realize that it was only 0-9A-F. That made the confusion of 0(zero) and O(upper-case 'oh') less of a problem during transcription. I never understood it enough to modify any of it in a useful manner, but it definitely helped avoid hunt&peck typos for a kid
That reminds me of the evolution of magazine code listings, which eventually came with per-line CRC values. If I remember correctly, there was a mod for Atari 800 BASIC where it would spit out the CRC after you typed each line of code.
There used to be a magazine or book that had this one BASIC program that you had to type in really carefully. That program let you type in a bunch of hex characters with a CRC and would tell you if you typed a line wrong. The rest of the programs in the book while still just BASIC programs were printed all encoded as a bunch of hex digit lines. It was great, once you got it typed in you knew there weren't any typos. Then you could list or save or run it just like any other BASIC program.
That's actually where I was getting my BASIC code from to transcribe. I don't remember exactly which magazine, but in my fuzzy memory, I think it was Byte.
