# XEQ41 — The programmable RPN classic > 1983 programmable RPN calculator emulator with original microcode simulation. (iPhone/iPad app by Guillermo Guemez.) - Source: https://appshunter.io/ios/app/xeq41/id6805313195 (this page in markdown: same URL + `.md`) - Developer: [Guillermo Guemez](https://appshunter.io/developer/6805313197) - Category: Productivity - Price: Free - Rating: 5.00/5 from 1 App Store ratings - Age rating: 4+ - Requires: iOS 17.0 · 5 MB - Languages: American English - Released: 2026-09-01 - Data updated: 2026-09-18 - Monetization: free - User reviews in markdown: https://appshunter.io/ios/app/xeq41/id6805313195/reviews.md ## What is XEQ41? XEQ41 is a hand-written emulator of a 1983 programmable RPN calculator, running the original manufacturer's microcode on a simulated NUT processor. It is not a re-implementation of the machine's behaviour — it is a simulation of its processor, so the calculator on screen executes the same instructions the hardware executed, and does what the hardware did for the same reasons. THE DETAILS THAT GET TESTED • Hold a key too long and the microcode itself cancels the function and prints NULL. That is 7,100 instructions — 1.23 seconds at original speed. Nobody wrote a timer; the ROM does it, and it stays 1.23 seconds when you run the machine faster. • BEEP is four tones, not three: 578, 361, 722 and 578 Hz, because the microcode falls through into a fourth. The test was written expecting three and the machine corrected it. • The display is modelled as a liquid crystal panel rather than sampled as a register, so the half-built strings the hardware never showed stay hidden and the 174 ms blink it does intend does not. • Continuous memory. Close it, force-quit it, come back next week — it is where you left it. • Shift-ON puts up a running clock, exactly as the manual says. THE FACEPLATE IS DRAWN, NOT PHOTOGRAPHED Thirty-nine moving key caps, the glass and the annunciator row are all vector, generated from a measured coordinate table — sharp at any size, with no image assets anywhere. A key going down travels, closes the shadow beneath it and darkens. The fourteen-segment display face is ours outright, drawn from our own segment table, so no third-party font ships. Every key is an accessibility element whose label is composed from the printed legend, so VoiceOver says "x squared" where the plate prints x². WHAT IS IN IT • FOCAL programming, with program files in and out through Files • Extended Memory, with real file structure • Four ports for plug-in module images you supply • The 82143A thermal printer and its paper tape, once you supply its ROM image • Synthetic programming — the byte grabber runs • Saved machines that record what was plugged in and refuse to open as something else • Alarms, the clock, BEEP and TONE, LCD contrast, haptics • Fifty transcribed keyboard overlay cards • Three faceplate palettes, and an optional extra display for the stack or the machine's status • Seven FOCAL programs written for this app, free to use and modify HOW IT IS CHECKED Thirteen scripted scenarios run byte-identical against a second, independent implementation of the same processor. Six programs from printed sources reproduce their published answers, including a polynomial fit and a singular linear system whose correct answer is the degenerate one. All thirty coordinates of a published planetary ephemeris match to the seven digits the display carries. 673 tests. PRIVACY There is no networking code in the app at all. No account, no analytics, no advertising, no tracking, nothing collected. Everything stays in the app's own storage on your device. WHAT IT IS NOT It is not a general-purpose calculator — it is one specific machine, and if you have never wanted that machine it has nothing to offer over the one already on your phone. Third-party module images — the printer's ROM among them — are yours to import, not ours to distribute. COMPATIBILITY XEQ41 is functionally equivalent to the HP-41CX. XEQ41 is not affiliated with, authorized by, endorsed by, or sponsored by Hewlett-Packard. HP, Hewlett-Packard and HP-41 are trademarks of their respective owners. ## Key features - Original microcode simulation - Continuous memory - Running clock - FOCAL programming - Vector-drawn interface - Accessibility elements - Extended memory with file structure ## Frequently asked questions about XEQ41 ### Does XEQ41 have ads? No, XEQ41 does not contain any advertisements. The app is completely free and has no networking code, ensuring no tracking or advertising. ### What is the rating for XEQ41? XEQ41 has a perfect rating of 5.0 stars from 1 rating, indicating high user satisfaction. ### Is XEQ41 available on Android? Currently, XEQ41 is only supported on iPhone. The app is designed for iOS devices. ### How often is XEQ41 updated? The latest version, 0.8.4, was released on 2026-09-13, suggesting regular updates to the application. ### What programming language does XEQ41 support? XEQ41 supports FOCAL programming, with program files that can be imported and exported through the Files app. ### Can I use XEQ41 offline? Yes, XEQ41 has no networking code, meaning it operates entirely offline and does not require an internet connection to function. ### What is the age rating for XEQ41? XEQ41 has an age rating of 4+, making it suitable for a wide range of users. ### Does XEQ41 offer any in-app purchases? No, XEQ41 is completely free and does not feature any in-app purchases. All functionalities are available without additional cost. ## Version history (last 4 releases) ### 0.8.4 — 2026-09-13 • Fixed: tapping a module that cannot go in — one already plugged, or a peripheral this app does not emulate — switched the calculator off and on. It now says why, and leaves the calculator running. • Fixed: a file arriving by AirDrop while the calculator was busy could be lost. • A damaged saved machine can no longer take the app down when it launches. ### 0.8.3 — 2026-09-05 • Fixed: the calculator could stop responding to the keyboard for up to twenty seconds after several keys were touched at once — a phone in a pocket, or a hand brushing the keypad. It now recovers immediately. • The stack readout goes blank when the calculator is switched off, instead of still showing the registers. ### 0.8.2 — 2026-09-04 The ALPHA keyboard • R/S is now on the ALPHA keyboard. A program that stops to ask you something can be answered without putting the keyboard away first. • The HP letter keys are the default, so the letters sit where they sit on the machine. • "Done" is now labelled ALPHA, because that is the key it presses, and the hide control says Hide. Other fixes • Importing a module, program or font no longer overwrites a file of the same name already in your library. • Plugging and unplugging a module now switches the calculator off and on, as the hardware requires. A module removed from a running machine could otherwise leave it giving wrong answers. • The printer panel's controls are legible on the dark faceplate. • The keyboard overlay picks up key assignments made from the settings screens. ### 0.8.0 — 2026-09-01 No release notes. ## Apps similar to XEQ41 | App | Rating | Price | Category | | --- | --- | --- | --- | | [Inbox To Audio: Text To Speech](https://appshunter.io/ios/app/inbox-to-audio-text-to-speech/id6783052831) | 5.0 (1) | Free | Productivity | | [Buckets: Time Blocking Planner](https://appshunter.io/ios/app/buckets-time-blocking-planner/id6802607987) | 5.0 (4) | Free | Productivity | | [Dayfeed: Holiday Calendar](https://appshunter.io/ios/app/dayfeed-holiday-calendar/id6778334948) | 5.0 (1) | Free | Productivity | | [e-Scanner: Scan PDF & OCR](https://appshunter.io/ios/app/e-scanner-scan-pdf-and-ocr/id6790476934) | 5.0 (3) | Free | Productivity | | [Sit Still: Focus Timer](https://appshunter.io/ios/app/sit-still-focus-timer/id6803553337) | — | Free | Productivity | | [NoDi: Lofi Pomodoro Timer](https://appshunter.io/ios/app/nodi-lofi-pomodoro-timer/id6742693841) | 5.0 (10) | Free | Productivity | --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-18.*