"All Hewlett-Packard pocket calculators feature RPN logic- the most sensible logic system a pocket calculator can have!"
Illustration of HP's four-level stack system.
"If you will look at the keyboard of any HP calculator shown in this catalog, you will see that none has an "=" key. Nor are there any keys for parentheses. None are needed.
Instead, all HP calculators have a key like this: ENTER. Thanks to this key, and RPN logic, you get four major advantages you don't get with most other calculators."
Short explanation of RPN by HP, 1975.
"All Hewlett-Packard pocket calculators feature RPN logic- the most sensible logic system a pocket calculator can have!"
This beautiful short introduction to #RPN (Reverse Polish Notation) is from Hewlett-Packard's Pocket Calculator Buyer's Guide printed in 1975.