Sunday, February 26, 2017


If you arre an aging computer nerd like me, you probably have always preferred RPN calculators over algebraic calculators (the kind with an = sign).  Perhaps it is just being a rapscallion or the result of writing arithmetic parsers in computer science classes (where RPN really matters).  Or maybe it's just my weirdness.  But while my wife was paying a mental health visit to a thrift store, I was trying to use an algebraic calculator on my phone called PowerCalc to calculate joules of energy delivered by projectiles at near-light speed.  In frustration, I downloaded an app called RPN Calculator which was quite reminiscent of my long departed HP 45, except for lacking the EEX button for entering scientific notation numbers.


  1. You and me both, Clayton!

    I still have my old Texas Instruments TI-55 RPN calculator(which was a ripoff of the HP45 but hundreds of dollars cheaper- and faster, too!)

    It was invaluable when I was studying Electronic Engineering back in the late '70s. Like you I still get confused at times, trying to do simple tasks on a non-RPN calculator.

    (Maybe it's just the old saw, "teaching old dogs new tricks," heh.)

  2. "ENTER" > "="... I still have a T shirt with that on it.

    You might enjoy "Free42", an excellent recreation of the HP-42 programmable scientific calculator (RPN, of course). You can find it at

    It is free, fast and powerful. I've used it for years.

  3. I feel your pain trying to use an algebraic calculator - how do people do this? I paid money for RealCalc for Android. Worth every penny.

  4. RPN is a must-have if you're doing any soft of serious computation. I own a couple of HP-35s calculators, one for the office and one for home. When I am away from one of those I use the RealCalc app from Quartic Software on my Android phone.

  5. I come from a long line of engineers. My dad got one of the absolute first HP35's in like '71 or '72.
    He let me play with it. I haven't been able to use an algebraic calculator since. Then, I did get my start on APL while working as a summer intern at IBM's Yorktown Heights facility.

  6. I use an HP48 emulator on all my phones and tablets. So reminiscent of my college days. I've still taken to programming some custom equations when required for the solver. Other friends of mine have the 42s or 41 emulators, too.

  7. Since everyone who has responded is an HP geek, I needed to respond as a person who always used the other kind. Starting from my first Ti-30 to my Casio FX-9700GE. But I will recognize some annoyance when I tried to get my PE in 2014 I was required to buy a Casio fx-115ES plus> They required it, any other calculators were taken at the entrance. Two years later I saw a notice that this model of Casio had become the calculator of choice for engineers. Right, actually hate it since it gives answers in fractions and certain Trig functions are nearly impossible to compute.

  8. I did some work in the FORTH language. Math in it is RPN, because all parameter passing is on a stack, done by pushing and later popping.

    If you haven't looked at it, FORTH is amazing in its ability to develop compact, high performance programs. It is also LISP-like in that most of FORTH is written in FORTH, and you can extend it - add new nouns, verbs and literal constants with ease.

    It has typically been used in embedded control systems, and was invented by Charles Moore to automate telescope controls at astronomical observatories. It never had wide usage, and is probably rarely used today.

  9. I got an HP-21 when it came out in 1975, when I was a grad student. Finally, one I could afford! Measure of my desperation: I drove from Durham NH to Brockton MA (about 90 miles) to get it.

    These days (however) I'm never far from a Linux terminal window. In my .bash_profile:

    alias calc="perl -ne 'print eval, \"\\n\"'"

    (Tricky bit is getting the backslashes and quoting right.)

    Example (input in italics)

    $ calc
    2 + 2
    355/113 - 4 * atan2(1,1)

    That last one I think was an example in the original HP manual, meant to show how close the fraction was to pi, although it was a little easier because the calculator had a π key, and Perl doesn't.

    355 ENTER 113 / π -

  10. uncle (PhD in polymer science) bought me an HP 11C as a present for high school. I used it all thru HS and college and still have the beast, 30+ years later (holy crap, has it been that long?).

  11. A bunch of us in Tech School got HP-35s' in '73, and my Dad (born in 1920) started using it for whatever he was calculating at his kitchen table when I accidently left it there in the late 70s... He took to it like a duck to water and used it the rest of his life.

  12. Real men use slide rules.

    John Henry A/K/A KC Boxbottom