About HP21 scientific RPN calculator
The HP-21 was a scientific calculator produced by Hewlett-Packard between 1975 and 1978. It was designed as a replacement for the HP-35, and was the first from so called Second Generation Handheld Calculators. As with...
The HP-21 was a scientific calculator produced by Hewlett-Packard between 1975 and 1978. It was designed as a replacement for the HP-35, and was the first from so called Second Generation Handheld Calculators.
As with most HP calculators then and now, the HP-21 used RPN entry logic, with a four-level stack. It also had a single user-accessible memory register. A shift key provided access to functions whose legends were printed on the fronts of the tall trapezoidal keys.
To enhance practical usability, display was modified to show both X and Y register. Also I have eliminated mechanical DEG/RAD switch and moved the function under DSP button.
HP21 has few big enough buttons to be used comfortably on mobile devices.
Previous Versions
Here you can find the changelog of HP21 scientific RPN calculator since it was posted on our website on 2016-12-25 17:15:35.
The latest version is and it was updated on 2024-04-23 09:56:38. See below the changes in each version.
HP21 scientific RPN calculator version
Updated At: 2019-05-07
Changes: Re-compiled to support Android 9
HP21 scientific RPN calculator version 2.7
Updated At: 2016-12-13
Changes: 2.7. Y^X complex result bug fixed (Error is shown for COmplex result),2.6. touch area re-alligned to buttons properly - thank you Eric,2.5. Can enter number by EEX button directly,2.4. To improve usablity - now running in full screen
Disclaimer
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