Learning RPN


Thanks for previous responses...

I'm learning RPN on my 41 since 2 weeks; you're all right it's easy to learn the basic. Even the majority of my physic students get it fast (but they find the calculator very ugly ;-) (high school students). I make some errors when the expression is more complex and still need my 83+ to verify... Is there a site with a lot of exercices and answers where i can test my skill with more complex arithmetic than dummy (3+6*5)^2/3 exemples in the user's manual. Even if it's not a RPN specific site? .... I also show them a HP-35 and some asked me why they made calculator for darkness with LED insted of LCD with backlight :-)))... i think i'm getting older...


Wonderful story about your students. This is the post-Nintendo generation. We are pre-vhs.

About learning RPN: may I suggest getting the Museum CD at http://www.hpmuseum.org/software/swcd.htm . It includes the HP-45 applications book: a 218 pages book with keystroke sequencies on math, statistics, finance, engineering and navigation. I am sure many other books in the CD set will help.


I bought these CD and use them for the HP-41 manuals only; thanks i'll check the others cd!!!


Zut alors! Ugly indeed! Le 41 est une merveille d'art de l'ingenieur. Votre etudients sont tres ingrat.


They prefer the colorful HP-30s and the "option" to change the keypad... :-)


Then there are no "true" engineers in the whole bunch!

By-the-by: I hope my message did not insult the French language.


Here in Texas we have a Calculator Applications competition at the High school level. A study a few years ago showed that over 85% of the students at the state championships used RPN calculators -- percentage is said to be higher nowadays. I have some of the tests they use on my website -- http://www.texasmath.org/DL. "They have several mechanics" problems, as well as Stated Engineering and geometry problems.

I probably should state that this contest was originally the Slide Rule Applications contest prior to 1980, hence the dependance on mechanics.

--Tony David.



maybe they are just used to no-keys, soft-finger-touch, paddle-stick-like control panels... What the h...! Before the keyboards and CRT, computers had switch-board and light panels. I'd not like to learn and use them...

The worst is that we (our pre-generation, I'm not included) saw stuff and tried to enhance, improve them. Today's 'etudients' are not interested on improving stuff, instead they are waiting for someone that will do it. The problem is that they are the ones to do it, and it seems they were not told about it.

About examples: there are good ones in some original Owner's Manuals for some calculators before the HP42S, but they are just a few ones. I'd add that the Voyagers are probably the last ones with authentic HP-quality manuals.

Renato gave a good tip; if you can, follow it.

Best regards.


>Before the keyboards and CRT, computers had switch-board and light panels. I'd not like to learn and use them...

A recurring programmer's nightmare is being forced to carry a large stack of punched cards (remember 'em?) and stumbling, falling, and several hundred cards scattered all over the floor. Now try to sort them so they're in the proper sequence again!

I'm glad I missed the card era.



You might be OK provided the card deck did not use "binary overrides". Reprint -- unless you were carrying the only copy!



My first year as an Electrical Engineer student: ForTran and punched cards (1979). You bet I don't miss'em, too.



You learned early on to draw a diagonal stripe with a magic marker or pen across the top of your card decks. This wouldn't give you a one-to-one ordering if (when!) you dropped your deck of cards, but would get you close when you reassembled them. You also named/identified the decks the same way (i.e. writing on the top) - the first FAT?

For my thesis, I ran a program comprised of a few hundred of those FORTRAN cards that read about 20,000 data cards (many boxes full, at 2000/box if I remember correctly).

I will still make the claim that a card deck was much better for random access to an arbitrary card than is a word processor file - if you don't remember any word on the card but knew about where it was in the deck. It's easier to find something "about 2/3 of the way through" by eye than by scanning line-by-line with your word processor!



Not bad, that trick with the diagonal line.

As far as cards vs. word processor, you simply cannot compare. A card deck is a database (even if it does not contain records of any sort), while a word processing document is a continuous stream of text. If you want to compare the card deck to anything of today, perhaps you should compare it against a database program such as Paradox or FileMaker.



For my first job out of school, I started at Boeing on the AWACS project. Security dictated a totally separate computer system and no dangerous network connections. Hence, all the surplus IBM gear (the keypunch machines and the huge gray "duplictor" and "interpreter" units noisily grinding through cards at about 1 per second . . . ) This was indeed culture shock after learning on a time-shared HP-3000 BASIC system in college.

What I liked about the card experience was the nice physical manifestation it provided what is generally a very ethereal profession. My "library" of utility routines was a rubber-banded stack of cards that I simply included (tacked on the end) of whatever program I was writing. I actually got to carry things around and move them in & out by hand . . . (And, fortunately, I was working in PL/I, perhaps the most "acceptable" of the IBM languages then available.)

I'm glad I experienced it, but I don't want to go back!


>(And, fortunately, I was working in PL/I, perhaps the most "acceptable" of the IBM languages then available.)

Ah, yes, PL/I. My one and only experience with that language was short-lived. The company where I worked took receipt of an AS/400 B45 back in January 1990, but having to relocate, I bid farewell in August of the same year.

During that time I wrote a complete system for the Human Resources department, all in PL/I, while the RPG compiler languished mostly unused. Sometimes I wonder how my replacement dealt with the PL/I programs, for I feel sure she didn't know a word of it. 8^)

The PL/I compiler for the AS/400 had a serious bug regarding external function calls which rendered programs buggy and unreliable. After reporting it to IBM, their reaction was to retire the PL/I compiler, which is no longer available on that platform. Apparently they didn't consider it worth their while to fix it!

Go figure. They killed their best programming language.



>I also show them a HP-35 and some asked me why they made calculator for darkness with LED insted of LCD with backlight :-)))... i think i'm getting older...

My niece has an HP-19B calculator, which she uses forwards and backwards. Once I showed her my old slide rule, and she couldn't figure out what it was for. She was born in 1974, the year of the HP-65.

Does anyone remember the logarithm tables??? 8^)



"Does anyone remember the logarithm tables??? 8^)"

Sure! I still keep a book of log tables on my bookshelf at work, as well as a couple of slide rules.


A couple of weeks ago, my daughter came to me for help with calculus. I pulled a copy of the CRC Standard Mathematical Tables (anyone remember those ?) and introduced her to the 700+ integrals inside, plus a whole lot more. She was amazed that this information was all in one book. She liked it so much she took it back to school with her.

It's a good thing I bought 3 of them for $1.00 each at a used book sale when I was in college. (...and dinosaurs roamed the earth.)


I showed them a slide rule (we have a objective in our program to show the evolution of some technology and i choose calculator this years) and they asked me how it works... I told them it's a log scale but when it came to do an exemple i was unable to satisfy this curiosity because i have no idea how to use a slide rule!!! - So i'm not so old. When i begun using calculator it was in 1979 and it was LCD (a TI-21). No more LED and slide rule in class; but my very first calculator was a nobility (clone of a TI-1200) i got on the knees of the "pere noel" (i don't know the english name of this personnage...)


"pere noel" = Father Christmas

Better known in English as Santa Claus (a contraction of "Saint Nicholas").

PS to use a slide rule, just remember that to multiply you add logs. The slide rule works by letting you add the logs (which are the lengths on the scale).



Using a slide rule is tricky at best. The absolute most basic concept is, as Dave has pointed out, that the scales are logarithmic. Of all the scales, C and D are the "main" ones. If you want to multiply 1.2 times 5, you move the "1" of the C scale so it is on top of the 1.2 of the D scale. Then you travel along the C scale until you reach 5, and read the answer in the D scale: 6.

Things begin getting complicated when you work with several multi-digit numbers, for then an answer (on the C or D scale) that reads "2" may, in fact, be 0.2, 20, or 2 x 10^-12. There are guidelines for placing the decimal point correctly, and I used to know them 30 years ago, but not anymore.

Also tricky is estimating numbers. You get at least 8-digit precision when working with calculators, but slide rules -- even the best ones -- rarely give you more than 3. Very large slide rules may give you 4-digit precision. Plus, the movements one makes when sliding the rule are never precise, and the errors tend to accumulate.

And then there are the _other_ scales (the typical slide rule has a couple dozen), such as CI, DI, CF, DF, A, B, S, T, ST, L, LLn, LL0n, and so on ad nauseam.

I keep my old Faber Castell slide rule as a memento, but whenever I need to calculate something, I pick up my HP-41CX.




About Slide Rules,

- Nice website : http://www.sliderules.clara.net/index.htm

- to make your guys jealous, I still have :

2 Staedtler/(13.5") No.54408 - Germany

1 Pickett & Eckel,Inc/(13") - Chicago,Illinois USA

1 A.W.Faber-Castell/(12") - Germany

1 Hughes-Owens/(11") No.1768C - Japan

1 Acme/(12.5") - Japan

and the wonderfull TI SR-50

The Red-Dot, ...not seen one yet !



I have some slide rules too:
Graphoplex 620d, 1614, 1614 mod, 640, 620d RIETZ, standard and soon 615 and 17cm;
Marc (unknown model)*,
Aristo Schollar 0903LL*,
Nestler Gamma 0253*
and Tavernier-Gravet (unknown model)*
* for sale on ebay ASAP

My engineering math classes were taken ca. the HP-21 . That is, log and trig tables were still easily located, slide rules were still widely used, and only the relatively well-to-do (student) could afford anything HP.

We were taught how to use tables and slide rules, and the question of whether to allow/encourage the use of calculators in class was an active debate among instructors for several uears.

I bought a Post Versalog from a local office supply store -- they'd dismantled their slide rule display and were selling off the display models. Mine has a screw hole in one end of the body, and doesn't move smoothly and uniformly throughout its range. (I suspect that it was chosen for display because it failed to pass Q.C.)

It served me fine, and I was able to locate the hard-cover instruction book, as well as the half-size model of the same rule -- a nice "family" collection.

I've also got my father's old Frederick Post rule -- an unusual model with some tricky scales -- he was a draftsman, specializing in layout and routing of hydraulic systems for Douglas Aircraft.

Interestingly, he'd carefully scraped off the manufacturer name and "Made in Japan" that had been embossed on the plastic face -- I suppose in 1950's America that anything Japanese was considered cheap, and he was probably ashamed to be using only a "second-rate" slide rule . . .

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