you often did get it wrong. However it didn't matter as when there was a mismatch you checked both the checksum and the line for errors. Generally you found errors in both, fix both go to the next line.
Getting all the typos out took almost as long as typing it in in the first place. I don't think I ever successfully typed in a program longer than 1 page, I recall being on page 3 of one program I never finished though.
It is so weird being on the spectrum and hearing stories like this. My dad and I often typed in multi-page programs without errors, or perhaps one error in the program.
I always thought it was OCD or something, where I would not enter a character unless I'd heard it unambiguously from the person reading the program to me.
Having it read to you would make it a lot easier to get it right, I would think.
My problem was always going back and forth between screen and magazine, and maybe skipping a line or a hex word or whatever. It took me longer than I'd like to admit to even figure out that moving a ruler down the page to help me find my place each time I looked back would reduce errors tremendously. If someone were reading it while another person types, it'd be much easier to not lose your place on the page.
I was mostly working alone. Most of my mistakes where omission. In the line
2560 data 0,0,0,0,0,0,0,0,0,0,0,0,45,0,0,0,0,0,0,0,128,42,128,128,9,0,0,0...
Missing one 0 is fatal, but the streak is long enough that it is easy to miss one and not notice.
Not getting the checksum wrong, getting the checksum tool wrong. While typing the source of the checksum tool, you don't have the checksum tool yet. Classic bootstrap problem :)
The checksum tool was short and came with its own checksum. Most of the ways you can type in a program wrong will cause the program will fail to run in some obvious way. Thus your first task was running the checksum tool against itself. The odds that you can make a typo that will cause the checksum tool to be broke and yet generate the correct output when run on itself were pretty low.
