**Non-Hewlett Packard RPN Calculators**

This is a list of calculators from the late 1960s and 1970s which used Reverse Polish Notation (RPN) for their calculation. Please note that the list in the original article has been expanded as further examples of RPN calculators have been reported.

For those unaware of the difference, the standard for 99% of electronic calculators other than Hewlett Packard was termed algebraic (arithmetic?) notation. To add two numbers for instance, you would key in:

**"12" "+" "3" and then hit the "=" key for the answer of "15"**

In a RPN machine, you would key in:

**"12" "enter" "3" "+" and the answer of "15" would appear on the display.**

We invite you to contact us with the manufacturer and model # of any non-HP calculator in your collection that uses RPN. A clue would be an "enter" key on the keypad instead of a "=". Please also let us know the method of power (battery, rechargeable batteries, or AC/line voltage only.)

(We omit HPs only because we know virtually all of their models used RPN. Only in the last few years have they added a non-RPN machine to the lineup.)

By the way, here's a question for you brought up by one of our contributors:

"One complication with classifying rpn/non-rpn is where the old "arithmetic" style fits—the ones with "+/=" and
"-/=" keys. I believe they function identically to the rpn style, except they have no enter key and only what we would call a two-level "stack". For example the Nat'l Inst. 400 (I believe?) is a
simple four-function LED calc that functions this way. They can just be ignored, but maybe there is a calc out there that fits somewhere between these classifications?"

Any comments or help from our readers????

Note: Here's a response to the question above from David Hicks, web-meister of the HP Museum --

"I call such machines "adding machine logic" machines. The HP-10 was HP's only adding machine logic
calculator. This style predates RPN by several hundred years and it's really stretching to call the two number registers a "two-level stack" because these machines supply no stack operations whatsoever.

Adding machine logic machines switch to infix notation when multiplying and dividing whereas RPN machines remain postfix. The size of the stack doesn't make a machine RPN or not. HP's first RPN models had 3
level stacks.

By the way, this "old" style is still in production on many business-oriented printing models. It's fine for sums of products - like most business forms."

Dave Hicks
(dgh@teleport.com)

The Museum of HP Calculators, http://www.teleport.com/~dgh/hpmuseum.html

RPN Calcs -- Version 2 (the version on this page will be changed as new information becomes available -- but we will not date it)

Thanks to Robert Bennett, Frank Boehm, Thomas Brockmeier, Rolf Brueckmann, Don Davis, Larry Gilbert, Kenton Green, Dave Hicks, Dave May, Joe Rigdon, Ken Sumrall, Erik Peter van Dam, and Tony Duell, Sergei Dolin for their inputs to date.

**Disposable or Rechargeable Battery Powered Models**

**APF:** Mark 55**Commodore** (USA): MM6X (just the "X" version, not all)**Corvus**
(USA): 500**Elektronika** (Russia): B3-19, B3-21, B3-34, MK-54, MK 61**Emerson:** E-12**GE
** (Australia): CE93**Heathkit**
(USA): 'Aircraft Navigation Computer' OC1401 (self-assembly kit version) or OCW1401 (ready-assembled version), aircraft navigation and scientific calculator**Magiclik:** 306**Montgomery Ward** (USA): P10**National Semiconductor** (USA): 600, 900, 'Mathematician', 4615, 4640**Novus
** (later name for National Semiconductor brand): 650, 3500 'Sliderule', 4510 'Mathematician', 4515 'Mathematician PR', 4520 'Scientist', 4525 'Scientist PR', 6035 'Statistician PR'.**Omron
** (Japan): 12SR**Prinztronic:** 'Programmable Scientific'**Privileg:** 'Beginner', SR-54NC, SR-55NC**Santron** (Japan or Taiwan): 12S, 604**Sinclair** (England): 'Scientific', 'Scientific Programmable'**Super Cal
**(??): 616

**AC / Line Powered Models**

**Anita** (Sumlock Comptometer, England): 1000, 1010, 1011, 1011P, 1020, 1021, 1000 LSI, 1011 LSI, 1011B LSI**Elektronika** (Russia): MK 56

**Friden (USA): EC130, EC132, 1151, 1152, 1160, 1166.Monroe (USA):** EPIC 2000, EPIC 3000

Copyright 1997 by Guy Ball, additional material 2022-2023 Nigel Tout

**Calculator Articles**

*Vintage Calculators *

Text & photographs copyright, except where stated otherwise, © Nigel Tout 2000-2024.