Panel meter calculator with floating point

Today I learned you can use generic GPIO PWM to fake an analog voltage.

https://ww1.microchip.com/downloads/en/Appnotes/90003250A.pd...

I didn’t actually know about the Casio 14-A until now. I almost thought the picture was AI-generated. Four functions squeezed into that compact desktop unit in 1957? Impossible with the technology of the time…

The Casio 14-A was indeed the world’s first all-electric desk calculator. But by “desk calculator,” they literally mean “a desk that is a calculator.” The display/keyboard pictured was literally attached to a desk filled with hundreds of relays and weighed 140 kg. [0]

The “all-electric” claim is interesting. There had been scores of electric calculators for decades (Friden, Marchant, etc.) but were merely driven by an electric motor. The calculations were still performed by gears and cams and linkages.

https://www.casioeducation.com/primary-calculators/14-a