When I first built a microcode emulator for the HP-29C, it came up with a flashing decimal point. I didn’t remember this being the case with the real thing; but that was a long time ago and I might have forgotten.

I had a vague feeling there was something about low power and a flashing dot. Perhaps it normally flashes but doesn’t if power is low. All of the earlier (“classic”) calculators had hardware driven low power indicators, and I didn’t have any hardware in the emulator for that, so the normal behaviour must be a flashing decimal point.

My daughter said, “it makes more sense for the dot to flash during low power as the consumption would be slightly less”. That’s where all of my thinking started unraveling. Continue reading HP-29C Flashing Dot →

Calculators often sit in loops waiting for their person to do something. The HP-29C is no exception. Here’s what happens. Continue reading HP-29C Wait Loop →