It might've been fast in simple cases compared to the alternatives, but there's no two ways about it that all computation takes time, and you can make tradeoffs where you cache more and compute less, but that's it.
It's not instant and unlimited. It's Limited and fast, or more limited and faster, or more ram and faster, or more data and slower.
Instant in this case means you move the brush and it distorts as you move the brush. No parallax, no beach ball waiting for it to do the computation. It happened as you moved it. It was instant. Even with brush sizes the size of the image you were using.
It had unlimited undo. It had unlimited layers. That's not an arguable point.
/me wonders why he even tries to point out the folly to people with no clue about how computers work...
It's not like people will think it's unlimited for real, there's no such thing.
It seems to me you are having problems interpreting words in context.
EDIT: I mean, if he said you could have 8K undos, or 8K layers and the response time is <15ms would that make you feel better? Does it make a difference?
So, by all means, continue to write software for those ideal beings that live in a world of comprehensible instantaneous and unlimited events, but you'll find that most people on this forum are operating under a different assumption.
Meaning they did not hardcode limits, and I assume had a O(1) or O(n) type scaling.
I'm not suggesting this is what they did, but if it was, would you consider that unlimited?
2) Obvious the answer is no, seeing that every time you DO ran into limits.
You don't have to use anything. You just have to know how computers work.
"Unlimited" in software can only mean: limited only by the computer's memory. Which is still a limit.
And "instantaneous response" with large images? I beg to differ. Maybe for the kind of image sizes used at the time...