6 ms·

Free42 – An HP-42S Calculator Simulator

80 points by abiro 3y ago

sytelus 3y ago
Amazing! Now, if you only have this for HP-48SX :).
- multiply 3y ago
  I enjoy Droid48 for this.
  - Tcepsa 3y ago
    My go-to for quick-but-slightly-involved calculations--I love having an HP-48 in my pocket! (and honestly, I appreciate the slightly-smaller form factor better than the original ;-) )
- deleted 3y ago
  [deleted]
joezydeco 3y ago
I've had the iOS version of Free42 in my pocket for over a decade now. My real 42S is safe in a drawer. Highly recommended.
Bud 3y ago
Am I the only one who think the 41CX totally outclasses the 42 series?
- whartung 3y ago
  The primary difference is simply the expandability of the 41 series, plus the hacking of synthetic programming. Outside of that, as a calculator, the 42s is a better, more capable device. Make no mistake, the 41 series was very cool. How many other calculators had floppy drives, plus whatever else you could wire into the 41. But the 42s is just flat out a better calculator. I have Free42 on my iPhone, but I typically reach for iHP48 over the 42. Just more comfortable with it.
- wrycoder 3y ago
  I have the iOS i41CX+ app. I love it.
- gumby 3y ago
  I still have my 41C, not that I use it much any more, plus some cards, case, and such. Wish I could find a good home for it.
banana_giraffe 3y ago
For anyone that wants a physical version, SwissMicros makes a calculator based off of Free42: https://www.swissmicros.com/product/dm42 https://www.swissmicros.com/product/dm42
- ralphc 3y ago
  That page says the HP-42S was "widely regarded as one of the most desired calculators ever made". Was it more "desired" than the HP-41C, with all the accessories that you could get for it?
  - nas 3y ago
    The 41C came out about 10 years before the 42S. Each would have their fans. The 42S doesn't have the hardware expand-ability but is generally faster and a bit more refined. If I wanted a nice handheld calculator today, I'd prefer the HP-42S or the Swiss Micro version. However, Swiss Micros have a 41C clone as well, if you prefer that.
    - maxflow2 3y ago
      The 42S was also mostly backward compatible with programs written for the 41C, intending to be its modern replacement. It did have an IR connection for some expandability (this was pre-USB era). I'll also note that, with regards to using an HP42S today, most of their LCD screens have not aged super well and have faded a lot. Other models like the HP15 and HP32S(ii) have LCD screens that seem to age a bit better for whatever reason (potentially the support for the menu and limited graphing behavior of the 42S required some slightly different LCD parts). I have all these models, but wouldn't recommend an original 42S to anyone but a collector due to screen visibility issues - my HP15C and HP32S are plenty usable still though. I also highly recommend the Swiss Micro replicas if you like RPN calcs. Very solid attempts at reproducing and modernizing some timeless calculators.
  - jjav 3y ago
    While I own a few HP calculators, my favorite is still the HP-28. Not sure why it isn't as remembered as the other models, but it's the one I still reach for whenever need to calculate anything.
crimsontech 3y ago
There is also Plus42 by the same person which is what I use on my phone. https://thomasokken.com/plus42/ https://thomasokken.com/plus42/ I have a 42S and 15C, I tend to use Plus42 the most, then the 15C.
antod 3y ago
The 42S was my calculator as a structural engineering student in the early 90s. I now regularly use the Android version of Free42 - I should try and find my old manuals though, so I could operate it as well as I used to.
FullyFunctional 3y ago
I have Free42 on my iPhone and while I don't use any of the advanced features, it has a level of polish that really makes it stand far from the crowd. Probably the most noticeable feature is the haptic feedback (enabled in the hidden menu under the logo). That feature and the full screen graphics goes a long way to making the calculator feel real.
idcrook 3y ago
I had an HP 42S in college. was best calculator I have ever owned, and had used the programmable features in it. I have used Free42 on Macs and iPhones for years. love it. Plus42 improves upon it by expanding the display size, suitable for the aspect ratio and size of iPhone screens and Macs
- jonsen 3y ago
  Thank you for the plus hint. Very nice. Worth the price.
userbinator 3y ago
This IMHO very important information is buried near the bottom of the page: The HP-42S represents numbers with a 12-digit decimal mantissa, and an exponent from 10^−499 to 10^499; Free42 Decimal uses a 34-digit decimal mantissa, and an exponent from 10^−6143 to 10^6144; and Free42 Binary uses native binary floating-point, which on all currently supported platforms is IEEE-754 double precision, with a 53-bit binary mantissa which is roughly equivalent to 16 decimal digits, with an exponent from 10^−308 to 10^308. In other words, results will not be exactly the same as a real HP-42S. For a more authentic HP-42S experience, there's Emu42. Also, just about every dedicated calculator uses decimal floating point for several reasons, such as simpler circuitry in the ASIC and keeping the human intuition that 0.1 + 0.1 is actually 0.2.
- nvy 3y ago
  The way you're using "decimal floating point" seems to imply there is a "floating point" that is not "decimal". My understanding is that "decimal", in the context of programming, is a less-precise term to mean floating-point (i.e. encompassing IEEE 754 floats, double- vs single-precision, etc), because they're all binary numbers if you dig deep enough, right? But apparently I am incorrect/underinformed about this. What is "decimal", then?
  - Thorrez 3y ago
    Decimal means base 10. Decimus is the Latin word for 10, and deci- is the SI prefix for 1/10, e.g. decimeter is 1/10 of a meter. Decimal floating point is x*10^y whereas binary floating point is x*2^y . Compare to hexadecimal which means base 16.
    - nvy 3y ago
      Derp. I misunderstood.
  - zokier 3y ago
    IEEE-758 floating point standard defines decimal formats, decimal128 is relevant here, I believe that is what free42 uses: https://en.wikipedia.org/wiki/Decimal128_floating-point_format https://en.wikipedia.org/wiki/Decimal128_floating-point_form...
nologic01 3y ago
This reminded me that after 30 years I need to change batteries on mine.
tigerlily 3y ago
This app is my daily driver. It was hard to find in the App Store though when I searched for rpn calculators, it was a huge relief to find it. Little known perhaps but you can tap the display to bring up the main menu. From there you can optionally select a different skin. I use GDW-Modern-i5, a nice clean darkmode with orange highlights. Edit: actually you have to download new skins from a gallery webpage first via what I can only describe as a tiny embedded web browser you can bring up by clicking "Load..." in the bottom left corner. Truly this must be God's own calculator app.
dm319 3y ago
I've used the free42 (and newer plus42) app on my phone for nearly a decade now. In the UK, RPN calculators were pretty much not seen in the school place. We had Casios, Sharps, and those really into maths tended to get TI graphing calculators. The beauty of RPN is that you can get the data into the calculator before you figure out how you're going to calculate the thing you want to know. The roll and x<>y help you to manipulate the data, and once you get the hang of it, algebraic notation feels slow and unintuitive (back pedalling through notation to get brackets in place for example). You also get intermediate results to sense-check as you're going along. I recently got a DM42 from swissmicros, which is a real life calculator running free42. It is beautifully made, and it makes me happy that I have it. But my job isn't in one place, so I still probably use the phone app more.

80 points by abiro 3y ago

sytelus 3y ago

Amazing! Now, if you only have this for HP-48SX :).

multiply 3y ago
I enjoy Droid48 for this.
- Tcepsa 3y ago
  My go-to for quick-but-slightly-involved calculations--I love having an HP-48 in my pocket! (and honestly, I appreciate the slightly-smaller form factor better than the original ;-) )
deleted 3y ago
[deleted]

joezydeco 3y ago

I've had the iOS version of Free42 in my pocket for over a decade now. My real 42S is safe in a drawer. Highly recommended.

Bud 3y ago

Am I the only one who think the 41CX totally outclasses the 42 series?

whartung 3y ago
The primary difference is simply the expandability of the 41 series, plus the hacking of synthetic programming. Outside of that, as a calculator, the 42s is a better, more capable device. Make no mistake, the 41 series was very cool. How many other calculators had floppy drives, plus whatever else you could wire into the 41. But the 42s is just flat out a better calculator. I have Free42 on my iPhone, but I typically reach for iHP48 over the 42. Just more comfortable with it.
wrycoder 3y ago
I have the iOS i41CX+ app. I love it.
gumby 3y ago
I still have my 41C, not that I use it much any more, plus some cards, case, and such. Wish I could find a good home for it.

banana_giraffe 3y ago

For anyone that wants a physical version, SwissMicros makes a calculator based off of Free42: https://www.swissmicros.com/product/dm42 https://www.swissmicros.com/product/dm42

ralphc 3y ago
That page says the HP-42S was "widely regarded as one of the most desired calculators ever made". Was it more "desired" than the HP-41C, with all the accessories that you could get for it?
- nas 3y ago
  The 41C came out about 10 years before the 42S. Each would have their fans. The 42S doesn't have the hardware expand-ability but is generally faster and a bit more refined. If I wanted a nice handheld calculator today, I'd prefer the HP-42S or the Swiss Micro version. However, Swiss Micros have a 41C clone as well, if you prefer that.
  - maxflow2 3y ago
    The 42S was also mostly backward compatible with programs written for the 41C, intending to be its modern replacement. It did have an IR connection for some expandability (this was pre-USB era). I'll also note that, with regards to using an HP42S today, most of their LCD screens have not aged super well and have faded a lot. Other models like the HP15 and HP32S(ii) have LCD screens that seem to age a bit better for whatever reason (potentially the support for the menu and limited graphing behavior of the 42S required some slightly different LCD parts). I have all these models, but wouldn't recommend an original 42S to anyone but a collector due to screen visibility issues - my HP15C and HP32S are plenty usable still though. I also highly recommend the Swiss Micro replicas if you like RPN calcs. Very solid attempts at reproducing and modernizing some timeless calculators.
- jjav 3y ago
  While I own a few HP calculators, my favorite is still the HP-28. Not sure why it isn't as remembered as the other models, but it's the one I still reach for whenever need to calculate anything.

crimsontech 3y ago

There is also Plus42 by the same person which is what I use on my phone. https://thomasokken.com/plus42/ https://thomasokken.com/plus42/ I have a 42S and 15C, I tend to use Plus42 the most, then the 15C.

antod 3y ago

The 42S was my calculator as a structural engineering student in the early 90s. I now regularly use the Android version of Free42 - I should try and find my old manuals though, so I could operate it as well as I used to.

FullyFunctional 3y ago

I have Free42 on my iPhone and while I don't use any of the advanced features, it has a level of polish that really makes it stand far from the crowd. Probably the most noticeable feature is the haptic feedback (enabled in the hidden menu under the logo). That feature and the full screen graphics goes a long way to making the calculator feel real.

idcrook 3y ago

I had an HP 42S in college. was best calculator I have ever owned, and had used the programmable features in it. I have used Free42 on Macs and iPhones for years. love it. Plus42 improves upon it by expanding the display size, suitable for the aspect ratio and size of iPhone screens and Macs

jonsen 3y ago
Thank you for the plus hint. Very nice. Worth the price.

userbinator 3y ago

This IMHO very important information is buried near the bottom of the page: The HP-42S represents numbers with a 12-digit decimal mantissa, and an exponent from 10^−499 to 10^499; Free42 Decimal uses a 34-digit decimal mantissa, and an exponent from 10^−6143 to 10^6144; and Free42 Binary uses native binary floating-point, which on all currently supported platforms is IEEE-754 double precision, with a 53-bit binary mantissa which is roughly equivalent to 16 decimal digits, with an exponent from 10^−308 to 10^308. In other words, results will not be exactly the same as a real HP-42S. For a more authentic HP-42S experience, there's Emu42. Also, just about every dedicated calculator uses decimal floating point for several reasons, such as simpler circuitry in the ASIC and keeping the human intuition that 0.1 + 0.1 is actually 0.2.

nvy 3y ago
The way you're using "decimal floating point" seems to imply there is a "floating point" that is not "decimal". My understanding is that "decimal", in the context of programming, is a less-precise term to mean floating-point (i.e. encompassing IEEE 754 floats, double- vs single-precision, etc), because they're all binary numbers if you dig deep enough, right? But apparently I am incorrect/underinformed about this. What is "decimal", then?
- Thorrez 3y ago
  Decimal means base 10. Decimus is the Latin word for 10, and deci- is the SI prefix for 1/10, e.g. decimeter is 1/10 of a meter. Decimal floating point is x*10^y whereas binary floating point is x*2^y . Compare to hexadecimal which means base 16.
  - nvy 3y ago
    Derp. I misunderstood.
- zokier 3y ago
  IEEE-758 floating point standard defines decimal formats, decimal128 is relevant here, I believe that is what free42 uses: https://en.wikipedia.org/wiki/Decimal128_floating-point_format https://en.wikipedia.org/wiki/Decimal128_floating-point_form...

nologic01 3y ago

This reminded me that after 30 years I need to change batteries on mine.

tigerlily 3y ago

This app is my daily driver. It was hard to find in the App Store though when I searched for rpn calculators, it was a huge relief to find it. Little known perhaps but you can tap the display to bring up the main menu. From there you can optionally select a different skin. I use GDW-Modern-i5, a nice clean darkmode with orange highlights. Edit: actually you have to download new skins from a gallery webpage first via what I can only describe as a tiny embedded web browser you can bring up by clicking "Load..." in the bottom left corner. Truly this must be God's own calculator app.

dm319 3y ago

I've used the free42 (and newer plus42) app on my phone for nearly a decade now. In the UK, RPN calculators were pretty much not seen in the school place. We had Casios, Sharps, and those really into maths tended to get TI graphing calculators. The beauty of RPN is that you can get the data into the calculator before you figure out how you're going to calculate the thing you want to know. The roll and x<>y help you to manipulate the data, and once you get the hang of it, algebraic notation feels slow and unintuitive (back pedalling through notation to get brackets in place for example). You also get intermediate results to sense-check as you're going along. I recently got a DM42 from swissmicros, which is a real life calculator running free42. It is beautifully made, and it makes me happy that I have it. But my job isn't in one place, so I still probably use the phone app more.