There were peripheral cards for the Apple II that would snapshot memory and write it to disk. You could use these to copy most games/programs. But there were st

There were peripheral cards for the Apple II that would snapshot memory and write it to disk. You could use these to copy most games/programs. But there were still a couple games that would periodically check that their disk was still in the drive for which this wouldn't work. Edit, oh it's mentioned on the Spiradisc page: > Spiradisc was used on Sierra's "Frogger" and "Maze Craze Construction Set" titles. It truly was state-of-the-art. My favorite trick was the way they defeated NMI copy cards, which captured a snapshot of the computer's memory after the game had loaded. The easiest trick -- corrupting your stack pointer when the game is idle, so the interrupt frame overwrites a valid return address -- was too obvious, and too easily circumvented. Instead, Spiradisc collected some information about the computer's configuration as it was booting. This was periodically re-checked. If the computer had mysteriously gained or lost peripherals, the game knew it was running on a different computer, and would bail. This meant that memory-image copies would appear to work until you tried using them somewhere else, which, as intended, had me running in circles for a few days (the copy card was in a friend's computer). https://fadden.com/apple2/computist.html https://fadden.com/apple2/computist.html