Nonpareil is an open source microcode-level simulator for electronic calculators. The software simulates some of the HP calculators introduced between 1972 and 1982.
Simulation fidelity is achieved through the use of the actual microcode of the calculators. Consequently, the simulation behaviour exactly matches that of the real calculator. In particular, numerical results will be identical, because the simulator is using the BCD arithmetic algorithms from the calculator.
Nonpareil attempts to run the simulation at the same nominal rate of microinstruction execution as a real calculator, e.g., 3500 microinstructions per second for an HP-55.
Nonpareil requires the GTK+ toolkit.
Key Features
- Simulates the following calculators:
- HP-35, HP-45, HP-55, HP-80;
- HP-21, HP-25;
- HP-31E, HP-33C, HP-34C, HP-37E, HP-38E, HP-38C;
- HP-41CV, HP-41CX.
- Simulates an 82143A printer.
Website: github.com/brouhaha/nonpareil
Support:
Developer: Eric Smith
License: GNU GPL v2

Nonpareil is written in C. Learn C with our recommended free books and free tutorials.
Related Software
| Calculators | |
|---|---|
| Qalculate! | Powerful and easy to use multi-purpose desktop calculator |
| Genius | Desktop calculator, an educational tool in mathematics, and for research |
| SpeedCrunch | High precision and powerful desktop calculator |
| KCalc | Scientific calculator designed for KDE |
| Calculator | Simple and easy to use calculator |
| KAlgebra | Replace your graphing calculator |
| rpCalc | Simple RPN calculator |
| Kalk | Cross-platform application built with the Kirigami framework |
| Modular Calculator | Aimed at scientific, engineering or computing work |
| Nonpareil | High-Fidelity calculator simulator |
| Wombat | High-precision scientific calculator |
| Uno Calculator | Port of Windows calculator |
| SwitchCalc | GTK4 calculator |
| Schulrechner | Calculator you know from school |
| Pebbles | GTK-based app |
| Cuneo | Widget-like calculator and conversion tool |
| RCalc | RPN calculator |
| galculator | RPN and algebraic calculator |
| Extcalc | Multifunctional scientific graphic calculator |
| gdcalc | Financial, scientific, statistical and programming calculator |
| Sums | Postfix calculator designed for quick calculations |
| Free42 | HP-42S calculator simulator |
| Yesser Calculator | Extensible calculator |
| xcalc | Simple scientific calculator that can emulate a TI-30 or an HP-10C |
| x48ng | Reboot of the HP 48 emulator |
| tCalc | Simple calculator written in core Tcl/Tk |
| OxiCalc | Small, simple calculator. It uses GTK4. |
| MCalc | Perform simple mathematical operations |
| Eigen | GTK4 matrix calculator |
Read our verdict in the software roundup.
Explore our comprehensive directory of recommended free and open source software. Our carefully curated collection spans every major software category.This directory is part of our ongoing series of informative articles for Linux enthusiasts. It features hundreds of detailed reviews, along with open source alternatives to proprietary solutions from major corporations such as Google, Microsoft, Apple, Adobe, IBM, Cisco, Oracle, and Autodesk. You’ll also find interesting projects to try, hardware coverage, free programming books and tutorials, and much more. Discovered a useful open source Linux program that we haven’t covered yet? Let us know by completing this form. |

