RPN-55 SD 3.3 - App Store

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About RPN-55 SD

RPN-55 SD is the first photo-realistic simulation for the iPhone of Hewlett-Packard's low-cost alternative to the famous HP-65 programmable scientific calculator. Produced from 1975 through 1977, it was the "Merlin"...

RPN-55 SD is the first photo-realistic simulation for the iPhone of Hewlett-Packard's low-cost alternative to the famous HP-65 programmable scientific calculator. Produced from 1975 through 1977, it was the "Merlin" member of the classic HP calculator series, priced at $395. HP claimed that it featured "(...) more pre-programmed functions than any other scientific pocket calculator in the world." A main feature of the HP-55 was a crystal-controlled 100-hr digital timer with the ability to store times while the timer was running and later recall them. On RPN-55 SD the timer may also act as a 12-hr or 24-hr clock, including date and weekday display. While the simulator works just like the original calculator - except being much faster and having twice the program memory - you can turn on extended features to make it even more enjoyable to use. RPN-55 SD comes complete with original HP programs built in. Features: . Photo-realistic look-and-feel . Vintage mode or Extended mode . Programmable (99 steps), conditional branching . Insert and delete steps with automatic address correction . Delete range of steps . Subroutines (4 levels) . 20 registers, "continuous", with unrestricted store/recall arithmetic . "Live" register view . Program listing view . Program library view . Store and retrieve any number of programs . 100-hr timer supporting 10 split times and 12/24-hr clock mode with date . Swap unit conversions with additional functions, e.g. hyperbolics . Sharing: e-mail, AirDrop, Dropbox, copy, paste, print . 112 programs pre-installed Calculator functions: . Statistics (linear regression, mean, standard deviation, correlation coefficient, x- and y-estimates) . Trigonometric functions (degrees, radians, grads) . Polar/rectangular conversions . Inverse, square root, logarithm, exponential, pi . Storage arithmetic (store and recall) . Percent, absolute, integer, fractional value, round . Factorial . Random number . Unit and hours conversions Details: cuveesoft.ch/rpn55

Version History • Improved compatibility with iPhone Air and iOS 26. 3.3 10/17/2025 Bug fix: If non-volatile memory is enabled (Calculator Mode = on), reloading the app does not clear the stack register X anymore. 3.2 07/28/2025 • Faster startup: no delay until the first button press is recognized after switching on. 3.1 05/08/2025 • Added warning when attempting to replace a Sample Program. • Visual adjustments to iPhone 16 Pro and iPhone 16 Pro Max. 3.0 10/22/2024 • Internal optimizations and cleanups. • Modified Info screen to avoid clipping by the Dynamic Island. 2.9 01/13/2024 • Both slide switches may now be operated either by moving them with the finger, or by simply tapping them. • The haptics level may be selected in Settings. • Like on a real HP-55, executing SST on step 00 in RUN mode simply ends any user input value. The next SST will execute step 01. • Runs on Apple Silicon Mac (see notes on homepage cuveesoft.ch). • RPN-55 SD requires iOS 12 or later. 2.8 12/19/2023 Like on a real HP-55, executing SST on step 00 simply ends any user input value. The next SST will execute step 01. 2.7.2 01/09/2023 • Fixes a crash when trying to Export a program 2.7.1 10/09/2022 • Haptics Set the haptic feedback level in the calculator's settings. „Sounds & Haptics“ / „System Haptics“ must be on in the iPhone's settings. • FileListView can be dragged down 2.7 09/29/2022 • Change the program listing font with a simple tap on the new button "F" • Apply a filter to quickly find any program. • Sample Programs may be hidden in the list of programs. 2.6 04/09/2022 • Improved sample program "Solve f(x) = 0" 2.5 10/05/2021 • Improved mail subject when mailing a program as PDF • New sample program "TVM - Solve for i" • Visual feedback when reloading programs in file list view Bug fix: • GSB command could not be pasted as text in PRGM mode 2.4 12/15/2020 • Print (or mail as PDF) the program or its description • A program running longer than one minute will emit a short beep when executing the final GTO 00 command • Improved accuracy in extreme cases of y^x with positive, integer x. For example, 1.0000001^(2^27) = 674530.4707, not 674530.4760 • New programs: "Nominal vs Effective Rate", "Num. Integration - Gaussian" • Call up "What's New" anytime from Info screen • Compatibility with iPhone 12 Bug fixes: • Fixed display issues when using the iPhone in "Zoomed" mode • The RND function didn't work correctly in regions using a comma as decimal point • Programs mailed in calculator view incorrectly showed step 00 • Double- or triple-tapping the empty program listing could cause a crash. 2.3 11/08/2020 • n! now appears as x! in advanced mode to reflect the fact that the function can handle non-integer arguments. • Added and updated sample programs. Be sure to tap "Reload Sample Programs" in program list. Bug fixes: • Fixed a bug occurring when single-stepping a programmed number input • Automatic mode switching based on the loaded program didn't work as expected in some cases 2.2 09/16/2020 • Stack shows localized formatted value while number is being entered Bug fix: • GTO/GSB to step 01 would halt program execution 2.1 09/02/2020 • Improved stack display (swipe display right to show): - Shows unformatted values of x and Last x - Long-press to directly call up the register view - Correct digit entries by swiping left • Email programs directly from the program list • Decimal points now occupy a full digit position. • In Vintage mode, non-zero values less than 1 are now shown without a leading zero, as does a real HP-55. In addition, numbers may be entered with leading zeros. • In 12/24 hours timer modes, tap ENTER to switch between time and date with weekday display. • Programs now always stop after a step 99 (instead of continuing at step 01) • Single-stepping on number input ends input mode • Replacing registers by pasting a program into the display is now optional • Support for iOS 13: Dark Mode, file sharing Check out the new Download walk-through on the website (under "Sharing".) Bug fixes: • Executing the summation command ∑ with a very large argument would cause a crash • Automatic address correction would produce values larger than 99 in some cases RPN-55 SD now requires iOS 11 or later. 2.0 01/25/2020 • Improved LNx! function: - Higher accuracy - Now returns y and z such that x! = y * 10^z (where z is an integer) • Program added: "Exponential & Log Curve Fit" Bug fix: • Sharing could cause a crash 1.2 08/14/2019 • Optionally replace unit conversions with additional functions (in Settings) • Added "x-estimate" for a given y to linear regression functions. Note that the key for correlation coefficient (r) has moved one row up. • Programs saved in vintage mode are now marked with a "V" in the listing view. • Added programs "Hyperbolic Functions", "Gamma Function (Toth)", "Solve f(x)=0", "TVM with Unknown Interest" as well as all test statistics programs from the book "HP-55 Statistics Programs". • Tight program loops with many repetitions will no longer cause the display updates to slow down. Bug fixes: • Pressing EEX when a number showing separators was displayed would not remove the separators • Touching a main register value would not dismiss the register view • The % function showed as 1/x in program listings • Deleting a range of steps using g CLP in RUN mode could modify unaffected branch commands 1.1 08/12/2019 1.0 07/02/2019

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Previous Versions

Here you can find the changelog of RPN-55 SD since it was posted on our website on 2023-09-25 11:09:02. The latest version is 3.3 and it was updated on 2026-06-24 10:45:42. See below the changes in each version.

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