Chuck Moore on stack size, stack operators and function arguments

[knife31]

Hey
Back in the 70's I thought I would never figure out the stack. Now I can't use a regular ='s calculator. People at work want to use my HP-11 and it's fun to watch them look for the equals key.

That being said how did HP decide that RPN was the way to go, did they use Forth or RPN exclusively for basic and advanced math and were there holdouts.
RH