Free42 Port of HP-42S for iPhone now available


A port of the excellent Free42 calculator (HP-42S simulator) was posted last night to the Apple App Store for the iPhone (and iPod Touch). Here is the description.

"42s is a port of Free42 which is a complete re-implementation of the HP-42s RPN calculator. There are no ROMs or emulators involved making 42s fast. Additionally, Free42 provides enhanced functionality over the original calculator such as over 25 digits of internal precision."

More info and screen shots here:


This isn't Thomas Okken's intended version--rather, it is Byron Foster port which Thomas is hoping to expand in order to allow for convenient program I/O, among other other things.

Actually, this $5 app seems pretty well indistinguishable from the beta version Thomas gave me to play with a few weeks back. There is no program I/O yet, the printer output is cleared between launches of the program, and Shift > Catalog > MEM reports 65536 bytes, even though much for of the device's RAM is available to the app., e.g 1000 ENTER Shift Matrix NEW dimensions a new 1000 x 1000 matrix in no time.

I am assuming this is but the first release of a fine app that will be elaborated over time with expanded features so it has the I/O capability of the Palm, Windows, and Linux versions.

I may send Thomas a note to learn what is happening?



Well, I hoped, Free42 also means that it is free... ;(


Hey, $4.99 for a HP42!, whats not to like


Thomas Okken has always advised me that there would be a token charge, if only to cover development costs and the fees associated with posted to the App Store. This off course would require a new name since Free42 would no longer make sense.

My only disappointment in this release of Byron Foster is that it is (hopefully) an incomplete work in progress. The lack of program IO, which we have in i41cxp, is a bit of a bummer, and the lack of persistence of print out contents is, I hope, a bug.

Like I said, hopefully this is just the initial release of an application that will be updated and improved in short order, as Antonio Lagana has done so diligently with i41cxp.

That said, I have fired a note to Thomas in the hope of some clarity.



The $5 price is intended to cover the costs of doing iPhone development, i.e. having to buy a Mac and the iPhone developer program subscription. While I can develop for Windows, Linux, Pocket PC, and PalmOS, at zero cost apart from a generic PC and a copy of Windows (both of which I need for many other reasons anyway), iPhone development is a slightly more elitist affair. ;-)

Susan Mackay has already finished another port which includes much of the functionality that Les and Egan were talking about, including program import/export and saving print-outs. We have yet to decide who will post this on the App Store, who will maintain it, and what we will charge for it, but rest assured a full-featured port will become available in due course, with source code made available under GPLv2.

Please be patient!

- Thomas


with source code made available under GPLv2.

I purchased the $5 version to support your efforts and ranked it with 5 stars just because it was GPL. I had no problems downloading the iPhone 42s code and building it on my Mac and running it in the iPhone emulator (part of Xcode--free BTW). Any anybody can do this without an iPhone developer subscription. The caveat, is that you can only use the emulator, you'll have to pay $99 for the privilege of compiling it for your phone. The upshot is that when I learn all this Objective-C stuff I can actually contribute.

Thanks for making the code open and available and easy to build (when I said I had no problems, I should have said that none would have problems, you just open the project and click "Build and Go").


I purchased the $5 version to support your efforts...

So did I :)
BTW I like it alot; There are only a few things to fix still it's beautiful, lightning fast :)

Thanks. My collection is almost complete.



  1. PRLCD does not print properly.


  1. Key click. I would prefer an option to just use the standard iPhone key click.
  2. Cannot toggle to printer output until after program runs. With i41CX+ I can watch printer output while program runs. I use this to debug and kill programs early if the results are incorrect.
  3. I like the QWERTY option for Alpha, but it is not well integrated. E.g. when programming LBL brings up QWERTY, but if I wanted LBL 01, then I have to use 0 from the QWERTY keyboard, then 1 from the keypad.
  4. Labels above keys hard to read (very small).

Feature Requests:

  1. Key click volume control (instead of master volume control).
  2. Allow toggle to printer while program runs.
  3. Printout email support.
  4. HTTP program browse and download.
  5. Email program send.
  6. A way to invoke/dismiss the QWERTY keyboard when in ALPHA mode. Swipe? Alpha button?

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP-41 module covers and side port cover Nate Martin 1 1,155 12-02-2013, 01:51 AM
Last Post: Giancarlo
  HP-70 Simulation for iPhone Willy R. Kunz 2 1,141 11-17-2013, 07:12 AM
Last Post: Namir
  Yet another benchmark port on the wiki: Savage Pier Aiello 35 6,969 09-26-2013, 03:22 AM
Last Post: Pier Aiello
  OT TI-59 for the iPhone Matt Agajanian 10 2,178 09-04-2013, 08:57 AM
Last Post: Eddie W. Shore
  Woodstock, Classic & Spices for iPhone Matt Agajanian 8 2,211 07-10-2013, 06:10 PM
Last Post: BShoring
  Re: RPN on an iPhone Pal G. 4 1,357 06-26-2013, 10:33 AM
Last Post: Pal G.
  HP 50G serial port programming Chris Smith 2 1,087 06-15-2013, 02:47 PM
Last Post: Chris Smith
  Great news - Vicinno's HP 15C Scientific Calculator iPhone app is FREE now John 21 4,626 06-07-2013, 05:49 AM
Last Post: Mike (Stgt)
  OT: RPN port to Casio fx-cg10/20? Matt Kernal 4 1,484 04-30-2013, 12:16 PM
Last Post: hugh steers
  HP-67 app for iPhone? Matt Agajanian 8 1,618 04-11-2013, 01:14 AM
Last Post: BShoring

Forum Jump: