I used OPS5 a lot myself, and I sold a commercial version with a UI on Xerox Lisp Machines in 1982 and the Apple Macintosh in 1984. Very hackable code, I modifi

I used OPS5 a lot myself, and I sold a commercial version with a UI on Xerox Lisp Machines in 1982 and the Apple Macintosh in 1984. Very hackable code, I modified it once to add RHS actions for spawning new data worlds and using them independently.