RPN vs Calc
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
RPN
This app is a photo-realistic simulation of a classic Hewlett-Packard programmable scientific calculator from the 1970s. It includes a 100-hour digital timer, clock functions, and original HP programs.
- Photo-realistic look-and-feel
- Programmable with conditional branching
- 100-hr timer and 12/24-hr clock
- Original HP programs built-in
- Extended features for enhanced usability
- Sharing via email, AirDrop, and more
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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
Calc
Explore the inner workings of classic TI-59, TI-58, and TI-58C calculators. This tool offers cycle-accurate emulation, a debugger to inspect code and registers, and a functional paper tape printer recreation. Load and save programs using magnetic card emulation and state files.
- Cycle-accurate TMC0501 processor emulation
- Integrated debugger for program and register inspection
- Functional PC-100C paper tape printer recreation
- Magnetic card reader for loading/saving programs
- State file loading for instant machine configuration
- Solid State Module support
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Calc-U-59 is a TI-59, TI-58, and TI-58C emulator for iPhone, iPad, and Mac. It runs the original ROM, so every program, module, and quirk works exactly as it did on the real hardware — with virtual magnetic cards, a PC-100C printer, all fourteen Solid State Software modules, and a CPU-level debugger for anyone who wants to look under the hood. CYCLE-ACCURATE EMULATION The TMC0501 processor is emulated at the cycle level, reproducing the exact behaviour of the original hardware — including the TI-58C's constant memory, preserved across restarts. The Master Library ROM and many more modules are included. INTEGRATED DEBUGGER Inspect program memory, data registers, CPU state, and internal SCOM registers live as the machine runs. Step through instructions one at a time, or let the emulator run and freeze it at any point. You can even run your own assembly programs! On iPad in landscape and on the Mac it sits beside the calculator; on iPhone and in portrait, turn on the debugger page in Settings. PAPER TAPE PRINTER A functional recreation of the PC-100C thermal printer with dot-matrix font rendering. Trace exactly what programs print and why. Copy output as plain text or as a high-resolution bitmap. MAGNETIC CARD READER Load and save programs and data registers as card files, stored on your device and synced via iCloud. Bring old listings back to life and run them under the debugger. STATE FILES Load .ti59 and .ti58(c) state files to instantly configure the machine with a program, registers, and flags — ideal for sharing reproducible scenarios or revisiting known machine states. SOLID STATE MODULES Select a Solid State Module and run programs from there. Whether you're bringing an old program back to life, running the Master Library modules, or exploring how these machines actually worked under the hood, Calc-U-59 gives you a faithful TI-59 in your pocket. Calc-U-59 is free software under the GPLv3; the source code is on GitHub.
Screenshots
Verdict
The clearest difference is price: Calc at Free against RPN's $1.99. Calc also leads on update cadence (fortnightly vs every 3 months). RPN's advantage is ratings volume (8 vs 2) and iOS requirement (12.0 vs 18.0). On rating, review sentiment, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Calc is free to download; RPN costs $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.
On the App Store both sit at effectively the same score — 5.0 for RPN against 5.0 for Calc. Both are backed by a comparable volume of ratings — 8 and 2 respectively. Written reviews split almost evenly too, at 100% and 100% positive.
RPN ships an update every 3 months, Calc fortnightly. The most recent releases landed on October 31, 2026 and October 28, 2026 respectively.
| Parameter | RPN | Calc |
|---|---|---|
| Price | $1.99 | Free — better |
| Rating | 5.0 (8 ratings) | 5.0 (2 ratings) |
| Positive reviews | 100.0% of reviews | 100.0% of reviews |
| Number of ratings | 8 — better | 2 |
| Update frequency | Every 3 months | Fortnightly — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Free — better |
| Devices | iPhone, iPod | iPhone, iPad |
| Requires iOS | 12.0 — better | 18.0 |
| Further details — not scored | ||
| Size | 17 MB | 9 MB |
| Age rating | 4+ | 4+ |
| Developer | CuVee Software | Martin Erzberger |
Customer experience
RPN
Calc
In-app purchases
RPN
No in-app purchases
Calc
No in-app purchases









