Bye bye Prime

[walter b]

Ok, let's try to structure the mess a bit (just by heart, I don't have any machine at hand right now):

1. From the HP-35 to the HP-42, I'd say, RPN was unambiguous in the HP world: 4 levels, top level repetition, roll - I suggest calling that classic RPN.
2. With the HP-28 and -48, infinite stack appeared and RPN was changed to RPL - that powerful UI that Don, Valentin, and others love so much.
3. Recently (i.e. with the HP-20b and -30b, but maybe more) a RPN dialect appeared featuring 4 stack levels plus an entry register as introduced with RPL.
   

I hope these are all the basic categories. They will need some polishing certainly.

d:-)