Poll - How long did it take you to gel with RPN/RPL?


Me? about a week of constant daily use.

When I first came here, I saw all the posts cracking on algebraic and thought: "Wow, these guys are kind of racist." Now that I have been using RPN/RPL for a while, algebraic seems awkward. Now I have to actually THINK for a second to remember how to do algebraic calculations.

Let's hear your 'transfer to the dark side' stories. ;)



The HP25 was the first calculator I had so that doesn't apply.


Got my 11-C in 10th grade, and was very excited about it---Read the manual (what a cool manual that was!) with my 8th grade brother looking over my shoulder. My first calculator, but had used my fathers TI SR-71? much previously.

The concept of the stack was such an natural and obvious advantage that I remember it being an epiphany of sorts.

Perhaps more telling was that my brother played with the calculator that one day, and then, having never used it again, borrowed it from me one day many months later, and he had no problem. RPN had "stuck" to him like glue.

He bought a 12-C when he got to college and has used it ever since.

(Normally, my calculator had very little "borrowing" demand since classmates would always be saying "where's the *^&$ sign!)


"My first calculator, but had used my fathers TI SR-71? much previously."

I remember being enthralled by a TI SR-51-II in the late '70s (similar to TI-59?). Being formerly in the USAF, I can assert with confidence that the SR-71 is a high-performance reconnaissance/spy aircraft that set speed and altitude records which still might stand today.

I don't find it difficult to go back and forth between AOS and RPN, having used AOS calc's from 1978 until getting a HP-15C in late 1983 after experimenting with the HP-41C in 1981.

I've bought the 28C, 48G, and 49G in the past year, and am still only semi-competent with RPL.


It was easy for me. In 1966, I went right from a slide rule to a Friden EC-132, a gigantic desktop which used RPN, and in fact had the whole stack visible right on the oscilloscope-sized CRT screen. It was nice: you could see exactly what was going on when you performed an operation.

When I got my HP-21 at work in '76, it was no problem.


I was 15 when I got my hp21, it took me about a week I used the excellent examples in the users manual.


My first HP was the 41CX in college 1982, late in the semester close to finals. It took me about a week to get the basics down and during finals I was bouncing between it and a TI-59 that I had picked up on clearance from an Ardans department store that was going out of business. From that point on I very rearly use that other type, and when I do, I have to really think about how to use them. I love RPN and will never give it up.



I had a TI57 in 1978 as my first calculator and it took me a couple of days to "master" the basics of AOS. I remember I tried an HP21 at that time and I found it awkward to use.

Later I bought an HP41C with a memory module. I had seen many TI machines at that time - TI58, TI59 - but I also saw an LCD-type calculator and felt amazed with that. So HP offers the HP41: alphanumeric and LCD display type.

It took me less than a week to undertand and use RPN efficiently, but it took me longer to program it with the same efficiency. I could repeat and enhance the examples, but I wasn't able to write a program from scratch. I remember that ISG and DSE were the "last barrier", together with the flags' concept. I cannot remember my first efficient program, but I remember it took me so much to "master" RPN programming that I was too tired to celebrate.

I wrote a lot of user-requested programs for the HP's, but I felt myself comfortable with direct access resources. I wrote a few programs for my own, and they remind internal functions: no interactive input, no labeled output. Like when you compute SIN, or LN, or y^x...

Wow! It's been a long time ago...

Luiz C. Vieira - Brazil


With RPL, maybe a minute? Although of course I wasn't competent to write
a program in that time. But I knew, deep down, as soon I realized how
the display model worked, that a 28C was a "must have" calculator. By
the time that I had nearly convinced myself that I really "needed" it
and might be able to afford it, even though it didn't have nearly as
much memory as my Sharp EL-5520 or it's I/O (well the 28C does have
output, but no input) and it was pretty expensive for a calculator, and
went back to the store for another look, it had been replaced by the
28S. I was writing simple programs (well, at least copying them from the
Owner's Manual, understanding how and why they worked, and writing my
own slight variations) the first evening that I owned a 28S. So much
more straightforward than writing a BASIC program for the Sharp or
recording an algebraic entry keystroke program for my little Radio Shack
calculator. How could anyone ever go back to those?

After experiencing RPL, I could never go back to algebraic entry (or
writing a BASIC program) for anything that I could justify writing a
program for, although I do keep batteries in the Sharp and various cheap
calculators that I have. The Sharp mostly for old time's sake (and it's
easy on batteries when not being used), and the cheap ones because they
fit in a shirt pocket, although I have to think about how they work when
I use them. Actually, my old Lloyd's from around 1980 and my Radio Shack
from the late '80s still work on the original batteries; amazing, even
though they're rarely used.

I'd have to say that it was more the case that algebraic entry never
really "gelled" with me. It never did seem "natural" to press an
operation key like + before entering the next argument; how can you add
two numbers when you've only keyed one of them in? I kept pressing the =
key after keying in the first number and then keying in the next number
which replaced the first number and left me very frustrated, so I
considered calculators to be a pain in the neck to use, although they
were useful enough to be worth a little pain. RPN (or RPL) entry seems
natural for me. I did buy a TI SR-51A when they came out with that
(about 1975) with it's heavily advertised algebraic entry, but I found
it to be rather a disappointment (although quite useful), and stopped
rebuilding the battery pack when I got a cheaper scientific calculator.
With RPL, calculators are easy to use and program (and fun to play

But of course, I had started out with pencil and paper and slide rule,
which pretty much force one to do numerical calculations in an RPN

And at various times I'd used adding machines. One of them in the front
office at work even did multiplication, but I don't remember whether it
did division as well. It didn't even need batteries or have to be
plugged in, you just cranked the handle to get the answer. I wish I
could've seen it with the covers removed. I hope that it didn't get
trashed and that someone treasures it; it was a very impressive machine
and I'd love to have it for my own.

The first electronic digital calculator that I ever got my fingers on
was a Canon which needed to be plugged in and used Nixie tubes for
display. Not programmable of course. It just did the basic arithmetic +,
-, X, and /; nothing so sophisticated as square root. That was around
1971, and it was certainly a wondrous device. I pretty quickly developed
a routine for finding square roots far more accurately than a slide rule
could, but as a practical matter, for "real world" problems our input
data was approximate (I doubt that it was accurate to three significant
digits) and slide rules were much faster and more convenient. But the
calculator was fun to play with. I found that it had a problem with
dividing by zero. When it did a calculation, the various cathodes in the
Nixie tubes flashed on and off while it was working on it. When I tried
dividing by zero just to see what it would "think" about that, the
cathodes in the tubes near the the right side began flashing, and the
flashing moved leftward until all of the cathodes in all of the tubes
were rapidly flashing. The only way that I found to get it to quit was
to turn it off. I left it going bonkers once for the owner (one of my
shipmates, who I guess had spent about a month's pay on it) to see when
he wandered into the shop. He looked as if he were about to have a heart
attack, but he more or less calmed down after I turned it off and back
on, tried it out, and found that it seemed to work perfectly. I never
did tell him that I had any idea of what had caused the problem; I
wonder whether he ever discovered how to make it do that. He's certainly
smart enough to know that it doesn't make any sense to divide by zero,
but I'm not so sure that he'd be curious enough to try it on a
calculator just to see what would happen or careless enough to do it by

Sure brings back a lot of memories.



Got my first HP-41 in 1983 or so, and it took me
a day or two to "get it", but then I was totally
hooked, and have been confused by algebraic
calculators ever since.
I sold that first 41, and got myself another.
I finally "upgraded" to a 48 in 1991, but I've started
to drift back to my 41 recently.
I also have one or two 41 emulators for my Palm, to
help me survive.


My first intro to RPN was the 9100 series somewhere around 1970. They had one at the radio observatory when I was a grad student. I was doing simple programs in minutes on that. (Of course, I hadn't been polluted yet by any "conventional" calculators.) RPN seemed a perfectly natural way to do things, and I don't remember ever having to stop and think about it. You could pretty much look just at a formula and evaluate it.

I analyzed my thesis data on my mechanical engineer Dad's HP35 one weekend when I was at home. (this might have been Christmas 1972.) With no previous experience, I developed a 10-step or so "program" (i.e. the order in which I had to hit the keys to enter and process several numbers per line of data) in a few minutes. Then I spent two days number crunching. The alternative would have been to punch all the numbers onto IBM cards and write a little fortran program.


My first experience with RPN was in 1974 playing with the HP-35 and HP-45 sold in Macy's. I was already a calculator fan and had read everything published on the subject I could get my hands on (two articles in Popular Science). I had a couple of HP brochures that explained RPN -- one was "ENTER vs =". (If anyone has this one, PLEASE POST!!!)

With brochures in hand, I practiced on the display models. (Macy's had a display with the -35 and -45 locked into security cradles, so I could play to my heart's content without bothering the salesman. Although I did get the manuals from him once.)

I don't ever remember having trouble understanding RPN. It all seemed perfectly natural at the time. So I guess the answer to the question is Gel Time = 0.

Unfortunately I had nowhere near the money to buy either of these gorgeous beasts and used other machines for the rest of the 70's. I returned to the RPN fold in 1979 and never looked back.

(But for three months in 1976, I actually had a Paying Job programming TI calculators. I had a fun time. Maybe I should write this stuff up for the Memories Forum.)

- Michael


Learning RPN (in the HP-35 "flavor") came easy because I'd worked somewhat with a Series 300 calculator from Wang Laboratories. This was ca. 1969, and the Wang used RPN.

(Great old nixie tube machine -- take a look at the Old Calculator web museum:


and scroll down for the Wangs.)

I don't recall ever spending much time agonizing over the learning process with the Wang. It all went pretty quickly, and by the time I got the 35 several years later, I found reviving the knowledge was simple. In addition, it really helped that the 35's manual was (is) a marvel of conciseness.

Also, I was very struck by the way the 35's manual got the newbie owner to actually use RPN before he had officially learned it. That's immensely reassuring. And I recall the 25's manual did a similar trick in getting the novice to write and run a program -- again before you were supposed to know how to do it.

Now when you compare those manuals with what you get these days....!


Best regards,


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