View Full Version : Machinists RPN Calculator

08-17-2001, 02:10 AM
I'd jump at the chance to buy a new 11c or 15c.
What a great little calculator. I'm trying to remember what my 11c cost me new? Around $55.00 comes to mind but it might have been more.
How many of you remember Educalc catalogs? Weren't they great!

08-17-2001, 02:10 AM
Looking at my HP 15C as we speak (write?).
Purchased it in 1985 and it been appropriately abused. This baby definately "takes a licking and keeps on ticking".

Spent 15 yrs in the service with me - has logged over 3000 Flight hrs and a BA degree and is now my primary work utility in the shop.

Would never trade it or sell it. Can barely read some of the function keys. The kid cut his teeth on it, it's been immersed in water, and dropped so many times that I'm sure it has surpassed any ISO cert shock test standards there are.

This wasn't meant to be a testimonial - just one hell of a product.

08-17-2001, 02:23 AM
Can't just be us. I looked on Ebay and 11c calculators are going for over $200.00!

Don Clement
08-17-2001, 03:51 AM
My first calculator was an HP35 that I bought back in 1972. I still use an HP41C everyday. RPN is the language of calculators. Why micro-sloth would supply such a pathetic non-RPN desktop calculator is beyond comprehension. RPN calculators have no equal...and no = key!

Don Clement
Running Springs, California

[This message has been edited by Don Clement (edited 10-05-2004).]

John McGlynn
09-30-2004, 09:50 PM
A while ago a few blokes lamented the lack of a decent RPN calculator.
I agreed with them, having grown up with an HP41C so I've tried to fill the gap (I hope). If anyone wants to try it, email me on jmcglynn@navigate.com.au and I'll send you one. Feedback is welcome. Size is 400kB.
It works on Windoze machines but I've only tested it on W2000 and XP.
On installation the manual is a word doc in the Program Files/RPN directory.
Try and Tell!



10-01-2004, 12:35 AM
My old HP-35 calculator, the original floating point RPN (reverse Polish notation) scientific calculator, from 1973 is still working. 30 Years+ used daily and still going strong. I will be really unhappy when it quits. One of the best investments I ever made.

I had to remove the battery pack and install a capacitor across the terminals to filter the output of the AC adapter.

I heard that they are now "collectors items". One is in the NY Museum of Modern Art permanent desingn collection. To me it is just a really good tool.

John McGlynn
10-01-2004, 12:47 AM
Wow! 30 years. All the old ones (including my HP-45) have suffered LED burnout over the years. A bloke I worked with a few years ago was still using his 45 even though about 10 of the leds were not working. He knew the kind of answer it should show and compensated to fill the missing digit leds.

J Tiers
10-01-2004, 12:52 AM
I had an HP41CV working until relatively recently. Then it died (grrrrrrrrr), and has resisted efforts to fix, even though I have the HP repair manual etc on CD.

Unfortunately, there is a diagnostic software rom, and the contents of that were and are still secret.....nobody who knows is talking, even though I doubt HP would repair one any more. Their policy has become 5 years and out.
(That's not to mention that the Corvallis division was closed and the work outsourced to India/China years ago, according to my information)

Somewhere I might still have my old LED HP21....maybe I'll pull that out. It was working when replaced...not used since.

[This message has been edited by J Tiers (edited 09-30-2004).]

10-01-2004, 01:25 AM
Led burnout on old calculators:

I always turn the unit off after each use.
The on/off switch has needed a bit of help over the years but still works.

10-01-2004, 03:34 AM
I still have an old TI that uses rpn, my dad gave it to me for x mas 1977, works fine.

I like the newer ti35 solar(i never do math in the dark), $14, if it catches fire I give it a fling, and get a new one for $14

In college I pounded a lot of numbers,mosty trig for surveying,machine shop math was easy.

Mike W
10-01-2004, 05:02 AM
I have 5 HP's up to the 48GX. I have found a few RPN calculator programs for the computer. Long live RPN. http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

10-01-2004, 02:32 PM
I still have my HP45 and it just refuses to die.

10-01-2004, 03:59 PM
What is reverse Polish notation?

10-01-2004, 04:31 PM
<font face="Verdana, Arial" size="2">Originally posted by J Tiers:
I had an HP41CV working until relatively recently. Then it died (grrrrrrrrr),
[This message has been edited by J Tiers (edited 09-30-2004).]</font>

Didn't know anything bout these calcs until


Holy mackrel. Must be really nice calculators. JRouche

10-01-2004, 04:38 PM
<font face="Verdana, Arial" size="2">Originally posted by mikem:
What is reverse Polish notation?</font>

RPN is a stack based operation, where the operator of the operands are entered last.

For example, in a conventional calculator, you enter

[8] [+] [4] [=] and it displays 14

On RPN calculator, there is no [=] key. Instead you do the following

[8] [ENTER] [4] [+]

In a simple example like this, you have the same number of key strokes, but when you have multiple operations, you can save a lot of key strokes by using the stack to store intermediate values. Also, there's no need for bracket operations, since you enter the expression from inside out, instead of left to right. This also helps you catch errors.

I think scientific calculator are no longer in such demand by professionals, and as such it's been relegated to school use only. I see fewer and fewer people using RPN calculators. Frankly, I can't remember the last time I used my HP41, and I'm in engineering design work.

[This message has been edited by rotate (edited 10-01-2004).]

10-01-2004, 05:04 PM
If you enter:

[8] + [4] [=]

and it returns 14, you *really* need a new calculator.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things

10-01-2004, 05:45 PM
Some old machinists have to use a different radix http://bbs.homeshopmachinist.net//eek.gif


[This message has been edited by nheng (edited 10-01-2004).]

J Tiers
10-01-2004, 10:59 PM
<font face="Verdana, Arial" size="2">
I think scientific calculator are no longer in such demand by professionals, and as such it's been relegated to school use only. I see fewer and fewer people using RPN calculators. Frankly, I can't remember the last time I used my HP41, and I'm in engineering design work.

Possibly....I use a calculator a lot, for engineering design work.

I like RPN because I can put in the numbers first, and decide what to do with them later.

Also, with RPN, if you start at the "inside" of an equation, often you can evaluate the whole thing on the fly.

I don't have to figure out a "strategy" first, as I do with the "()" calculators that I am using now as substitutes.

10-01-2004, 11:21 PM
I love my Ti89. It can do 3d graphing, and I have a C++ compiler around here somewhere for it. It's more calculator than I could ever use. got a Z80 processor in it, I think 12mhz.

10-02-2004, 12:11 AM
I still use an HP-48SX with RPN for much routine engineering stuff and mathcad for more analytical work and excel for graphic logging of data.

I was one of the early owners of a TI SR50, first competitor to the HP35. Being a poor student, the $180 SR50 was a far cry from the $380-ish HP35. Also built a 4 function calculator back then and the TI chip was around $120 bucks. OK ... I was working too.

Both were a welcome experience over the K&E slide rules http://bbs.homeshopmachinist.net//smile.gif

10-02-2004, 11:01 AM
Here's a link to an outfit that will fix that beloved HP RPN calculator:


They did an HP32S for me last year for very little money. When it went out I just figured I'd trot down to the nearest university bookstore and replace it with the latest and greatest. NOT! Why Hewlett-Packard ever discontinued that model (and their other RPN calculators) I'll never know. Life without a RPN calculator is not worth living.

Kim Steiner

10-02-2004, 11:30 AM
I thought you could still get the 32S, am I wrong? I have one I bought a couple of years ago.
I'm still using the 20 year old or more 11c in the shop.
I've had 71's (not RPN though), 42s and a couple of 19's.
Love those old guys and wouldn't think of doing simple math without RPN, it's so much better.

Mike W
10-02-2004, 04:22 PM
HP still makes RPN:http://www.hp.com/calculators/

The Museum of HP Calculators:http://www.hpmuseum.org/

10-02-2004, 07:09 PM
I can see I'm gonna have to check out HP calculators from all these posts about them. I have half a drawer full of TI's, most of which worked for a week or two max. My old 1984 radio shack has never let me down yet though.

John Garner
10-02-2004, 08:20 PM
I'd be very happy to pay good money for a more compact version of the HP-11 or HP-15, something about the size of the Casio fx-260 (3 inch x 5 inch x 1/2 inch).

10-02-2004, 10:10 PM
And I lament the passing of the moderatly priced programables, such as the TI-68.

10-03-2004, 01:14 AM
<font face="Verdana, Arial" size="2">
Didn't know anything bout these calcs until
Holy mackrel. Must be really nice calculators.</font>

When I worked for Hughes in 1981-1984, we had all kinds of programs on a HP41CV to recheck our manual calculations.

<font face="Verdana, Arial" size="2">
I can see I'm gonna have to check out HP calculators from all these posts about them. I have half a drawer full of TI's, most of which worked for a week or two max. My old 1984 radio shack has never let me down yet though.</font>
I loved the 12C, simple and cheap. Of course it only had 5% of the functions of the last purchase, a TI85 graphing calculator.

10-05-2004, 04:02 PM
I remember the 35 and the 41CV. I thought when I bought the 71 it would be an updated 41 but it wasn't. It's good but I look at it like it was my first laptop. Actually it cost me about $400.00.
Yep RPN, every engineer's friend.

10-05-2004, 04:57 PM
This sure stirred up the cobwebs in the olde memory bank!....My first calc. was the HP-35, bought Mar./73 for the tidy sum of $400.00.....Came in a hard plastic case AND had a leather soft case.....Batteries are gone, but I just plugged in the AC adapter/charger and it fired right up.....Still have everything that came with it, including the cardboard shipping container.....

I now use my HP-12C (financial) or HP-15C (scientific) almost daily, and love the RPN logic.....Occasional use of an algabraic calc. seems clumsy and archaic.....

I was quite surprised to learn that RPN seemed to be going away in HP's line.....It's not that hard to pick up, and makes calculating much more flexible.....

I still have a TI-59 I bought because it was "programmable", along with the thermal printer and a bunch of software, but the HP's won out as far gettting used.....


Don Clement
10-05-2004, 05:36 PM

Did your HP35 have the original calculation error? (IIR, the error occurred when processing ln 1.01) Did you send your 35 back? I was in school at the time and wouldn’t part with calculator long enough to send it back, so the original error is still there.

Don Clement
Running Springs, California

11-28-2004, 12:57 AM
I've got an HP 11C and two HP-42s's. Boy, I'm going to hang onto those now (I was considering selling one or two of them). I keep the 11C and 42s in my shop and they're very convenient.

When you're around a computer, you can use calculator programs. Most of them are not RPN and if you've gotten used to RPN, you don't want to use an algebraic calculator. Here's a console-based (i.e., DOS window) calculator program that I wrote around 5 years ago. I literally use it every day both at home and work. It's compiled to run on 32 bit Windows machines.


11-28-2004, 01:38 AM
I discovered RPN in junior high school. I think the brand was APF. That old LED is probably valuable now from what I'm seeing here - moot since it's deep in the landfill now.

I replaced it with an 11C which seemed pricey at the time, but I was really happy to find another RPN calculator. A few years ago I found another 11C at a garage sale with the book for probably a dollar. Seller probably couldn't figure out how to work it with no [=] key. Good for me - now I have two. Use them all the time and I have a hard time adjusting to the "other" kind.

There's two kinds of people - RPN and Other. Started my new job a couple weeks ago and asked a guy if I could use his calculator. He grinned as I took it, expecting me to come back soon with questions. I noticed it had no [=] key so I did my figuring and handed it back, said thanks and gave him a knowing nod. He grinned again, but now it was more a "Cool! You're in the club, Dude" expression.

11-28-2004, 02:29 PM
To Don Clement;

Sorry this answer took so long.....

I didn't notice an error in mine, but that doesn't mean that it's not there.....Have to check.....Mine's been in storage for years since the I bought my 12C & 15C units.....

Does the error show up when 1.01 is used as part of the calclation?.....


John McGlynn
11-28-2004, 06:37 PM
LOoking at some of the posts here we really do love dem HP.

I've added a graphing and curve fitting facility to the calculator in the last month or two so if you want an update, just email me on jmcglynn@navigate.com.au

Comments are welcome. Especially criticism.


11-25-2005, 12:34 PM

[This message has been edited by Wirecutter (edited 01-28-2006).]