Hewlett Packard HP-15C Simulator | Hacker News Reader

Hewlett Packard HP-15C Simulator

hp-15c.homepage.t-online.de

82 pointsfortran7765 comments

HP rpn calculators are the best. I have 2 HP12cs on my desk that have accompanied me through my career in finance and still get used every time I want to calculate anything and don't want to crack out excel. To give you an idea how durable these things are, mine are later models using the inferior battery tech and poorer quality fabrication and are still running on their original batteries after 20 years of near daily use.

I fondly remember programming my dad's HP calculator[1] to do various important chemical engineering things when I was 10 or so.

There is a famous story about a zookeeper who was using an HP12C to calculate ratios for different ingredients and accidentally dropped it into the feed. According to the story it passed through the digestive tract of a hippo and was still able to calculate the yield to maturity of a bond after cleaning[2].

[1] Looking at old photos I think his was a 29C or similar. [2] Recounted here https://www.hpmuseum.org/hp12c.htm

Randomly/weirdly, I also 1) Have 2 HP12cs on my desk; 2) Used them first in my finance career and now in tech; 3) Have Hunter as a surname.

If you used to work in algorithmic trading and you are British then this would be truly weird.

Hah! I used to work in algorithmic trading at GS in London and I am British (an immigrant).

Well, nearly anyone in algo trading have a 12C lying somewhere :)

I find it sad that the knowledge of how to use calculators has declined, and as a result there is less market need for them, so they get discontinued (especially the good ones). I find a good engineering calculator indispensable.

The HP-15C is a really great one, although I usually prefer to use a much older HP-25 — it has most of the functions I need, and it can be used single-handed, which is a Big Deal. I even designed a Qi battery pack to make it useful in everyday life :-) https://partsbox.com/blog/wireless-charging-for-a-hp-25-calc...

I think learning an HP calc is a great investment of any engineer's time. For practical use, I find the HP-12C to be most useful for everyday things (because of percentage functions and date calculations), HP-25 for mechanical engineering and anything where I need to use a calculator one-handed, otherwise the HP-90 was the pinnacle of calculators in my opinion and I really like its unit-handling library. Do not automatically assume that the more recent HP Prime is "better" — in my opinion it is a contraption designed for university students, and I don't find it as useful for actual real work as earlier models.

The HP-15C is great, too, but I never use most of its functionality — for things like matrices there really are better tools. So you often end up using a small subset of what it can do, just to get the nice form factor.

On iOS, there are two apps that I'd recommend: "RPN-25 CE" is a great HP-25 emulator, and "Touch RPN" provides fast modern versions of the 12C, 15C and 16C (a programmer's calculator which I really like when writing embedded software).

I "got back into calculators" recently (middle age is sad), rediscovering the graphical calculators of my schooling days. Maybe at the time I knew how to use it properly, but re-learning how to use it now made me appreciate the power. I did make me wonder if taught properly, or I had shown more interest how many extra marks I would have gotten in exams.

I blew a TON of lawn-mowing money on the first graphing calculator I ever saw in probably 1987. It was a Casio, and it was AWESOME at the time. I wish I still had it.

> It was a Casio, and it was AWESOME at the time. I wish I still had it.

Casio 7000? I remember those being truly trendsetting. (And some of the later Casio's even introduced color.)

That's it!

https://en.wikipedia.org/wiki/Casio_fx-7000G

the screenshots on the Wiki article are giving me great nostalgia vibes.

When things get discontinued at the mass market level, it just means there is space for niche players. I'd argue that anyone wanting a classic HP-style calculator today is better off with one of the SwissMicros clones than a used original HP or a phone app:

https://www.swissmicros.com/products

(I have a DM42, and it is great as an object to fetishize the past. But in all honesty, it doesn't get that much use because the vast majority of the time, if I need to calculate something I'm already at a computer and reaching for the calculate is just more effort than opening a spreadsheet or a terminal window.)

> I have a DM42, and it is great as an object to fetishize the past. But in all honesty, it doesn't get that much use because the vast majority of the time, if I need to calculate something I'm already at a computer and reaching for the calculate is just more effort than opening a spreadsheet or a terminal window.)

Same experience here. I have a drawer full of HP's that never get used. Either the computer or a phone is always at hand. This was definitely untrue during the calculator's professional heyday 30-40 years ago.

I do have a 42 emulator on my phone that I use for occasional light calculations (tips, etc.). I used too much RPN in my formative years to enjoy using an algebraic calculator.

though swissmicro adds huge value to these calculators, the buttons are sub-par.

Personally, I am somewhat surprised that people like the HP-42. I don't find it to be a good compromise at all. The calculators that I like using are ones that are either relatively simple and small and don't try to do too much (like HP-25, HP-11C, HP-12C), or ones that are complex, but do unique things that are very useful (like unit conversions in the HP-50G). The 42 is neither.

As to sitting at a computer, I guess it depends on what your calculations are and how quickly you can reach for a calculator (mine sits smack dab in the middle of my desk, between the split halves of my keyboard). But a spreadsheet won't let me quickly multiply values that are in microns and get an answer in engineering notation.

I am also not advocating for "graphing calculators" — plotting functions on a calculator makes no sense these days, nor do matrix computations. The sweet spot has moved in the direction of simpler calculators, because you are not likely to do anything complex (like graphing) on a calculator today.

Which calculator do you mean by HP-90? I tried to find the specific model but couldn't find anything not desktop-sized.

I meant HP-50G :-) (sorry, not sure what happened there)

> I find it sad that the knowledge of how to use calculators has declined, and as a result there is less market need for them, so they get discontinued (especially the good ones).

It's probably because most jobs don't need them anymore, any calculations are done in pre-made software now, or in Excel. I've not had a need for a calculator other than fairly basic arithmetic (what's 10+9?) for years.

Why would I even bother investing time and money in a calculator when I can write a quick script in Python and not only do the computation but print sexy graphs as well? It's just more electronic waste in my opinion.

The HP-prime, which is I think the latest version of the HP line is also very good and supports both RPN mode and algaebraic mode (apart from a symbolic mode). There are also android, mac, and pc emulators available (and the pc version works under wine on Linux)

My only plaint is that I wish it had a qwerty keyboard, but then it would make it ineligible for AP exams. I never figured out why AP explicitly disallows calculators based on the keyboard configuration!

Android: https://play.google.com/store/apps/details?id=com.hp.primeca...

PC: http://www.hp-prime.de/files/HP_Prime_Virtual_Calculator_201...

Mac: http://www.hp-prime.de/files/HP_Prime_Virtual_Calculator_201...

Does the "HP-Prime" have good keys?

After the HP48 series, the keys on HP graphing calculators have been garbage.

Well it's worse than the hp48gx, and a bit better than the 49/50 models (well anything post 48gx).

I haven't used the others, so I can't compare. But I like the keys on the prime - they're hard rubber and make a satisfying click, and don't wiggle too much. Apparently the Prime-G1 had a contrast issue that affects visibility of the letters on the keys, but they fixed it in the Prime-G2.

It's sad but I heard HP already sold off the support and development of HP Prime to another company. There are still bugs to be fixed, but next firmware update may never come.

It's my favorite calculator. It's sad to see it's (likely to be) the last calculator that HP produces.

The best part of the old HP calculators are those lovely buttons.

Many of them were made with double shot injection molding. Rather than painting the label on the keycap, the label was molded into the key as a different color plastic.

This is generally in keeping with HP's overall level of engineering that went into these calculators. They used a series of custom microprocessors from the original HP35 on forward, and spent a great deal of time on numerical analysis to make sure the calculators produced good results. William Kahan was involved in this work for years. (Kahan was chief architect of IEEE-754, among his many other contributions to numerical analysis.)

YESSSSSS.

Having one of these in high school in the 80s was awesome. No one else could use it. LOL.

I lost the 15C I had, but bought the programmers' version (16C) on steep discount at my university bookstore in about 1990 or 1991. I still have it on my desk, for random arithmetic, though I've never used it for its notional purpose.

In later years, I've kept an HP clone / RPN calculator app on every device I've had, even back in the Palm days.

My first "pocket calculator" was an HP-45. I still have one on my desk, although I rarely use it because I don't want to burn out the LEDs, which do not age well into their 4th and 5th decades. Instead I use an HP-45 simulator on my phone. Somehow it just feels right.

I had a 15C in high school as well, as my father was a geek and told me he'd only buy me a calculator if it was RPN. I loved it, but I wore it out by the time I got to college and I replaced it with a 32SII. I've still got that one, but it long since died and won't turn on.

It's crazy how much demand there is for these. An original 15c is going for more than $200 on ebay and the limited edition re-release is going for more than $400. I was able to get the 15c re-release when they did it, wish they would have done a 16c re-release as well.

I recently received a free one of these at a garage sale. The daughter of the nuclear physicist who used it during his career had it out and said I could have it for $0.50. I didn’t have small bills or change, so she just gave it to me.

I knew “of” HP calculators, but hadn’t yet deep dived into _why_ they were cool. This kicked it off for me. It’s probably on the original battery.

I suspect maybe she knew it was worth a fair amount, but didn’t care. She seemed very zen with the idea of reducing the amount of unused items in her life. It was a very cool, eclectic sale by two home-based artists.

Not as much fun as the real thing. I've owned several HP calculators, going back to the 1980s. My 15C might be my favourite, actually, although my 35S is similarly pleasant to use. Frankly, though, the loveliest were those early-era ones that had rounded backs that were so comfortable to hold and use with just one hand. For me, they are the true classics for use in the lab or the field.

I also used a large desktop as a student. It might have been a 9100, but I'm not sure. The keys were great (always a prime aspect of HPs) and it was hooked up to a little plotter that was very handy for seeing what a complicated function looked like.

Come to think of it, the only non-HP calculator I ever used was a Sinclair Scientific. It was really fun, but it only lasted a few years before it had electrical problems. But for one-hand use, it was amazing. And it was tiny and weighed very little. It had a sweet little plastic case to protect it, so you could put it in a pants pocket with keys and there was no problem.

Good times with RPN.

There's a freeware version for IOS from Greg Hewgill

https://apps.apple.com/in/app/retro-15c/id583559000

HP also included one called xhpcalc in earlier releases of HP-UX.

Yes! I've been using this for years. It's great.

There’s an official HP version as well:

https://apps.apple.com/gb/app/hp-15c-calculator/id503720774

Well behind the times. Look at Eric's http://www.brouhaha.com/~eric/hpcalc/ which emulators the original ROMs.

Any simulator almost certainly lacks the numeric accuracy of the original.

I'm the primary numerical programmer behind the WP 34S (https://sourceforge.net/projects/wp34s/) -- essentially a superset of the 15C plus so much more. This stuff is not easy.

> Any simulator almost certainly lacks the numeric accuracy of the original.

Half the time, it's simply a result of relying on C's built in math (which pretty much translates to what your native ALU can do). I'm sure, as you allude to, the notion of doing more complicated and precise calculations is not normally considered.

Thanks. I tried to build it, and had to give up.

Stuck on "import as" in its scons-local/ .. /gas.py. Debian-packaged scons complains, instead, about syntax "except OSError , (errnum, strerror)" in top-level SConstruct, which I expect is a python3 complaint.

Also, Debian doesn't have gtk-2. Doubt it works with gtk-3.

Sad when software rots.

Still use an actual HP-12C daily. Been going strong for 35 years now and only had the batteries changed twice.

Had a 15C when I was an EE but it got sold on eBay when I discovered how much money it was worth.

I'll admit to having a working collection https://imgur.com/a/3eiSMPO

I have one 15C that belonged to my grandpa and another that belonged to my dad. Alas, I wonder what fantastic piece of technology will I hand down the line!

I had that 20S for years. Great calculator. Display went bad so I got rid of it. I wish I’d explored fixing it instead.

In spite of having no shortage of calculator apps at my disposal, I missed having a physical calculator so I actually bought a NumWorks calculator a couple of years ago. It’s a great calculator but there’s just something about that HP calculator aesthetic that I miss.

HP sold an official IOS version of the 15C for years but stopped updating it at some point. It still worked but didn't scale correctly on new iPhones. About a year ago I noticed that it had updated. It looks like they sold it to "Royal Consumer Products" aka hpofficesupply.com which is a licensee selling HP-branded (physical) calculators. It rotates between landscape and portrait mode and includes a full manual.

Royal said it's going to release new products this year. Keep your fingers crossed.

I have the HP-15C app on my iPhone and it's my primary calculator, even though I have pCalc.

I still have my 1987 vintage HP-15C, and it is an heirloom of my house...

I got my HP-15C in high school around 1987. Two weeks ago, I changed batteries on it, and I'm really not sure I have done that more than once before.

The device is a delight to hold and use (the buttons are unmatched in their feel), and it's fun to program with instructions listed as coordinates to the buttons on the device. RPN is such an elegant and compact notation in use.

I also have a HP-48SX, but it sees much less use – the buttons are not nearly as pleasant and the screen is harder to read. For a CS crowd, the HP-16C is the one to get (I found an emulated version very handy, when I taught Computer Architecture, and while I don't really need it, I certainly would like the Microswiss version).

> I also have a HP-48SX, but it sees much less use – the buttons are not nearly as pleasant and the screen is harder to read.

I have an 11C and both a 48SX and GX. I don't really think the keys on any of those were close to being in the same league as my Dad's old HP-38C.

https://www.hpmuseum.org/hp38.htm

Agreed on the display, but HP got it better on the GX.

In retrospect, all of the 48/49 series calculators struggled with their UX... The UI was complicated by their attempt to be a general purpose calculating tool, but the hardware wasn't up to the ambition and computers/laptops ate their lunch in professional settings.

The haptics of the HP-1xC were the best. I wish they would still be made in the original quality. The SwissMicros clones just aren’t on the same level (also their displays differ significantly).

Are they still in production? Is there actually any market for these calculators?

(I was an TI 91 and 48GX user in the until 2002)

HP does still make some calculators, but there's also SwissMicros who are making their own clones of them.

https://www.swissmicros.com/

Got 2 of them (DM-16L and DM42) and they are both excellent

How is the DM42? I really want one but don't need it :)

> Are they still in production?

The last official production run was the 15c Limited Edition (ARM7-based, similar to the refreshed 12c around the time) a little over a decade ago. This variant was special enough that it shipped with a CD containing the official PC emulator.

I managed to swoop two of them back then while a broke ass uni student (sold out quick). Ended up reselling one just to make ends meet before graduating, but kept the other just in case my 35s went tits up; I still use that 35s regularly at the office, but CalcTastic[1] makes a very compelling replacement mobile app.

> Is there actually any market for these calculators?

Who are we kidding? Between engineering and finance types, RPN diehards are a dying breed IMHO. Even if a new RPN calculator were to get NCEES approval[2] for use in the FE/PE exams, in practice, very good RPN apps on mobile abound after formalities are out of the way.

[1] https://play.google.com/store/apps/details?id=com.shaytastic...

[2] https://ncees.org/exams/calculator/

> Are they still in production

No, but:

https://www.swissmicros.com/products

There is also a DIY emulator on ATMEGA328 microcontroller: https://paxer.net/voyager/

> TI 91

Does not exist! You mean either TI-81, or TI-92.

HP-UX comes (or came?) with a simulator that could do a couple different models.

Maybe I'm doing it wrong, but I installed the font, started the program, typed in:

    2 ENTER
    3 ENTER
    +

and it spat out

    6.0000

Have I misconfigured it somehow?

Similarly

    2 ENTER
    5 ENTER
    +

spits out

    10.0000

You need "2 <ENTER> 3 +" to add two and three.

Your "3 <ENTER> +" is adding 3 and 3.

Thanks for clarifying. I didn't realize that the input buffer was separate from the stack.

For the classic HP RPN, it isn't. Numbers are entered directly into the X register. ENTER does several things: it finishes the input, copies the new value in X to Y (shifting the rest up) and inhibits "stack lift", so the stack won't be automatically shifted up when you start entering the next number.

Sounds complicated, but in practice you don't think about it at all.

Later calculators (the HP 42 and 48 lines) would basically accommodate either mode of operation. You can perform a calculation immediately without pressing ENTER to put it on the stack, or you could put it on the stack with ENTER first and it'll still do the same thing when you press an operator key.

I use an HP 48G+ frequently and I pretty much do both styles without any obvious rhyme or reason from my viewpoint. I just sometimes do one or the other.

I think you mean 28, not 42 — the 42 is also "classic" 4-register RPN. And I’m writing this mostly to push for the excellent Free42 emulator, which runs on just about everything (Windows, macOS, Linux, Android, iOS), and also powers the DM42 hardware emulator mentioned above. Only problem with it is that emulated buttons on a touchscreen are nothing like the real thing; I keep missing keystrokes.

I can confirm, the 28C actually shows the 4 (viewable) registries of the stack, numbered on the left as:

So, if you input 4 [ENTER], 3 [ENTER], 2 [ENTER], 1 [ENTER] you have:

4:4

3:3

2:2

1:1

But if you input 4 [ENTER], 3 [ENTER], 2 [ENTER], 1 you have:

3:4

2:3

1:2

if you then press +, you get 3 in both cases, which is the sum of the bottom two lines in the display.

Those are either the same as the "old" x and y registers or the sum of last input and the bottom register, same as the old x.

Yes you are right, I did mean that :)

It's easier to get how they work on calculator or emulator that shows bigger part of the stack

The combination of "simulator" and "online" in the post title & URL had me convinced this was a web-based simulation.

Consequently, I spent longer than I should've trying to tap the buttons on the screenshot.

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