This is where it all started for me, my first exposure to Apple. The first bit of money I ever made was writing a game called Library Adventure for the Apple II. Much of the code was written with peeks (to access hidden bits of the OS) and pokes (to hide our own stuff for later retrieval) in memory. We used packages from PenguinSoft and Beagle Brothers. Pulled many all nighters and had a grand old time.
Now the Computer History Museum and Digibarn Museum have released the Apple II DOS code into the wild (non-commercial use only). Here’s the link if you want to grab a copy for yourself. As of this writing, the server returned an internal error. I suspect the servers have been overwhelmed with requests.
Sigh. Such sweet memories.