Calculator for Electronics using Windows, HP-48GX

And Heres one for the HP 41CV.

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I have one on my Windows 8.1  and it works great, I also have the real one, I purchased for My Computer & Electronics College Courses a long time ago (1990s).
It uses RPN primarily but can also use algebraic notation.

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You can also download the manuals for free too! Just browse for HP 48G manuals.

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PS it has a plethora of built in programs
Electrical,
Hydraulics,
Columns and Beams,
Forces and energy,
gases,
heat transfer,
magnetism,
motion,
optics,
oscillations,
plane and solid geometry,
solid state devices,
stress analysis,
waves.
it uses labels that you can use to make formulas to identify your inputs or built in ones, and then solve for you, it also has pictures to help identify which components you can use such as parallel or series resistors and voltages.