If it doesn't have an Enter key, it's not RPN

[Michael de Estrada]

I recently bought a vintage calculator (JCPenney MM3R) under the mistaken assumption that it was a non-HP RPN. It lacked any sort of RPN indication such as a key labelled Enter or Ent or <up arrow> or even Input, although it did have keys labelled += and -= . A generally reputable eBay seller claimed it was RPN, however, that proved not to be the case. Apparently, the seller had only checked addition and subtraction, which are entered the same for simple operations, however, they are different for multiplication and division. So, 3 Enter 4 + and 3 += 4 += yield the same result of 7, but 3 Enter 4 X yields 12 whereas 3 += 4 X yields no result until += is pressed at which point the result is 16 ! So, basically, if you see an auction for a calculator w/o an Enter key claiming to be RPN, ask the seller to test multiplication to verify that this is true. Every single one of my many non-HP RPN calculators have some sort of Enter key on them, although I do know of a few exceptions such as the National Semiconductor NS600.

Note, I bought this calculator from a different seller than the one claiming it was RPN. This seller made no such claim.

[Steve Simpkin]

A variation of Adding Machine logic similar to the HP-10.

http://www.hpmuseum.org/hp10.htm

[Derek W]

The entry system using += and -= was quite common on early calculators. My first calculator (in 1974) was a model similar to that, sold as Commodore in UK, with a switchable constant but no memory keys. It cost me GBP30 at a time when my annual salary as a student engineer was GBP832, so maybe equal to GBP 500-600 or USD800-900 today. A mains adaptor was an extra GBP5.

It was a whole lot easier than a slide rule for approximate calculations or 7-figure log tables for accurate ones!

[MarkHaysHarris777]

(02-05-2015 08:25 PM)Michael de Estrada Wrote:  Every single one of my many non-HP RPN calculators have some sort of Enter key on them, although I do know of a few exceptions such as the National Semiconductor NS600.

RPN really does not have anything to do with whether the calculator has an equals key (strictly speaking); it is only really about whether the operator is 'postfix' or not. By definition, all ten-key adding machines are RPN. My wife is an accountant in the States, and we have several ten-key machines around the house. The classic TI5630, and the TI5033, are two examples worthy of note; and both have an equals key.... but, no one (accountants) ever press it! Those two machines have ONE very large key marked with a plus (+) which is strictly a 'postfix' operator (the minus operator works the same way). She will fly over that little box(s) clicking away at some gigantic list of tax receipts (or the credit card statement) and NEVER presses the equals key (not ever).
The other key she uses heavily is the (* T) key which is equivalent to the CLSTK function on the WP34s. The running totals (all postfix) need a grandtotal|clear in order to begin adding the next gigantic column of numbers (sometimes for the 11th zillionth time, just looking for that lost penny) Is that like a farthing six-pence in the U.K? <sorry random>
Well, there is a reason they are called 'adding machines,' at least here State-side. As it happens, she can multiply on her 'adding machines' (with the equals key) but she doesn't ever do it!
In fact, I was showing her the WP34s (bragging about not killing it with my soldering iron) and explaining the whole RPN thing thinking she wouldn't get it... she said something like, "of course, how else would you add on a calculator?" "... how come your (+) plus key is soooo small?" "... why didn't they call that big ENTER key over there the (+) plus key and put it down there on the lower right where it belongs?"
Some people's accountants! :-}

HP was not the first to build a calculator with RPN (although they are the ones to make RPN famous). Very honestly I think the quirks of the HP four level stack make the machines more famous than RPN, frankly. But certainly they go together. Adding machines do not have a stack (nor do they need one). Adding machines don't need to multiply or divide either (although just because its easy to make an adding machine into a four-banger, they do) and most people who 'need' an adding machine because they pound their large postfix (+) key all day long could care less whether their adding machine multiplies or not, let alone whether the * and / are postfix or not.

I say, RPN is as RPN does. RPN is in the eye of the beholder.

cheers,

[Thomas Radtke]

Very true, Mark, as we've recently seen different RPN implementations in early HP calculators. RPN isn't much of a standard beyond using postfix operators.

[Michael de Estrada]

Thanks to all of you for your contributions to this thread. I guess perhaps I should ammend my original post to say that the calculator I bought is not FULL RPN, since only some of the operations are postfix.

[d b]

Dave Hicks calls that 1/2 rpn the same thing that Steve S calls it, "adding machine logic". It's was built that way, or maybe that particular way became popular, because accountants and others used to using simple 2 function mechanical adding machines didn't have to change methods. Mark sort-of said that already.

It showed up a lot in the early days of calculators when companies bought a TI chip and built their own calcs around it. They often used that same += & -=, probably to save one key. The Privileg Beginner / Harvard 606, the supercal 616, and the Commodore 6 & 6x all had keys printed +=, -=, x= and /=. All were two level stack RPN, or postfix Only the 6 lacked an enter key but all could be used without ever pressing enter.

Thanks for putting the warning up Mike. Friends don't let friends buy non-rpn calculators.

[Didier Lachieze]

(02-07-2015 04:42 PM)Den Belillo (Martinez Ca.) Wrote:  It showed up a lot in the early days of calculators when companies bought a TI chip and built their own calcs around it. They often used that same += & -=, probably to save one key. The Privileg Beginner / Harvard 606, the supercal 616, and the Commodore 6 & 6x all had keys printed +=, -=, x= and /=. All were two level stack RPN, or postfix Only the 6 lacked an enter key but all could be used without ever pressing enter.

Not only in the early days:

[Steve Simpkin]

(02-07-2015 04:42 PM)Den Belillo (Martinez Ca.) Wrote:  "Friends don't let friends buy non-rpn calculators"

I'm putting that on a plaque on the wall

[rprosperi]

(02-07-2015 06:54 PM)Steve Simpkin Wrote:  

(02-07-2015 04:42 PM)Den Belillo (Martinez Ca.) Wrote:  "Friends don't let friends buy non-rpn calculators"

I'm putting that on a plaque on the wall

I was gonna reply the same way, but you beat me to it!

If you make such a plaque, make several, there will be many interested customers here; I'd like to be first in line (ok, 2nd).

[walter b]

(02-07-2015 10:22 PM)rprosperi Wrote:  If you make such a plaque, make several, there will be many interested customers here; I'd like to be first in line (ok, 2nd).

1+

d:-)

[Steve Simpkin]

(02-07-2015 10:22 PM)rprosperi Wrote:  

(02-07-2015 06:54 PM)Steve Simpkin Wrote:  I'm putting that on a plaque on the wall

I was gonna reply the same way, but you beat me to it!

If you make such a plaque, make several, there will be many interested customers here; I'd like to be first in line (ok, 2nd).

Here is a virtual example made at http://www.award.com. The HP-35 picture is from this site.

[Michael de Estrada]

In order to appease the RPN gods for my faux pas in mistakingly purchasing a non-RPN calculator, today I picked up two genuine non-HP RPN calculators, a Sinclair Scientific Programmable and a National Semiconductor NS600.

[d b]

Another fake rpn ad here:
http://www.ebay.com/itm/NON-HP-RPN-CALCU...4ae4bb1f72
One would thing one's reputation for honesty would be worth more than a couple of bucks.

[Michael de Estrada]

(02-11-2015 03:44 AM)Den Belillo (Martinez Ca.) Wrote:  Another fake rpn ad here:
http://www.ebay.com/itm/NON-HP-RPN-CALCU...4ae4bb1f72
One would thing one's reputation for honesty would be worth more than a couple of bucks.

Looks like the seller took your admonition to heart, and has revised the listing to remove any mention of RPN. Actually, this calculator was also sold as RPN previously by the same seller that claimed the JCPenney MM3R was RPN. They are both the same as the Commodore MM3R.

[Michael de Estrada]

I received another non-HP RPN calculator today, a Commodore Minuteman 6. It's a basic 4 banger with a 2-level stack with only integer math capability, so 3 += 2 /= yields 1 as the result. It has a switch that illuminates a fixed decimal point LED between the second and third digit from the right side of the display. It is very small, about the size of a pack of cigarettes, and fits easily in my small hand.

[Michael de Estrada]

I just won another auction for an RPN calculator. This time it's a Commodore Minuteman 6X, which differs from the model 6 with the addition of a proper enter key. The enter key serves to initialize a chained postfix operation and can only be used once, since the stack has only two levels and does not get raised after the first entry. This calculator includes its box and all documentation, including an inspection report, which is signed with the initials D B. Hmmm, I wonder who that might be ?

[TASP]

My HP80 does not have an 'ENTER' key.

[Michael de Estrada]

(07-15-2015 12:16 AM)TASP Wrote:  My HP80 does not have an 'ENTER' key.

Semantics. HP uses Save instead of Enter on the HP-80, and makes no mention of the 4-level stack in the documentation. Instead it talks about adding machine operations, which are the same as postfix. Basically, HP didn't want to scare financial types, who it regarded as mathematically challenged, and focused more on the built-in functions. Later financial models, such as the HP-22, returned to the Enter key, and documented stack operations the same way as the scientific models.

[d b]

Michael; To answer your year-old question: the page is back up. I'll have to add a couple of things.
Page One
I hope you don't mind me hijacking your old thread, but it seemed to fit here.

To anyone else: this is sort of like the "alternate universe" hp museum - the world in the mirror where RPN was implemented by everyone else. It grew out of a couple of emails between Dave Hicks and I in about 2000. And grew. And grew. Most of the calculators are owned by me. The site is maintained by Mike Davis. He used to post a lot on the old forum. For a few years, he, Katie, and Tony Duel were the ones that fielded most of the "how do I fix...." questions. They had a lot of generous help too.

He once posted that he had space if anyone wanted to display their calc collection. It started out with about a dozen. As I said; that grew. If I've missed any salient points, please let me know and I'll add them. This is meant to be an overview though. That's why I've added links to better descriptions when I know them.