Free42: An emulator for the HP-42S scientific calculator

Free42, developed by Thomas Okken, is a free, open-source re-implementation of the HP-42S scientific programmable calculator. Available across a variety of platforms, it reproduces most of the functionality of the original device and supports operations ranging from basic arithmetic to advanced scientific functions, consistent with the capabilities of the HP-42S.

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Designed for diverse calculations

Free42 supports a wide range of mathematical tasks, from basic operations to advanced scientific functions. It includes capabilities for complex numbers and matrix operations, as well as built-in trigonometric, logarithmic, and statistical functions. Free42 also maintains compatibility with the HP-42S programming model, allowing users to create and run calculator programs as on the original device.

Accuracy and functionality

Free42 provides high numerical accuracy and reproduces most of the functionality of the original HP-42S calculator. It supports both Binary and Decimal floating-point modes on desktop platforms, while the mobile versions use the Decimal engine only.

A modern way to use a classic calculator

Free42 brings the classic HP-42S calculator into today’s world in a simple and reliable way. It keeps the original functions people loved, from basic math to advanced science features, while adding the benefits of modern software. Open-source and easy to access, Free42 is a handy tool for anyone who wants a trustworthy scientific calculator with a proven design.

  • Pros

    • Open-source
    • Accessible across multiple platforms
    • Supports both basic and advanced functions
  • Cons

    • Mobile versions limited to Decimal engine
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App specs

Also available in other platforms

Program available in other languages



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Laws concerning the use of this software vary from country to country. We do not encourage or condone the use of this program if it is in violation of these laws.
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Is Free42 safe?

100/100

Score result: Clean

This file passed a comprehensive security scan using VirusTotal technology. It is safe to download.

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Scan Info

Last scan
Wednesday, September 24, 2025
Scan provider
VirusTotal · Full report

File Integrity

File
Free42_V3.3.8.zip
SHA256
4fcf192895bd65e3f1bf2912ffcdbc7a2617555f9b8a8f9a8f87db13eedf2ff7
SHA1
08135c4576e6ca3889b79afeeb6dbd62949709dc

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Free42 has been thoroughly scanned by our advanced security systems and verified by industry-leading partners. This file comes from the official developer and has passed all our security checks, showing no signs of viruses, malware, or spyware. For more information, visit our Security and Trust Center