HP-10 (KISS) Emulator

[[kby]]

Which is the same behavior as the real calculator and now I think I know what is happening in both cases.
The first += puts the original 4-digit number in the summation register (think of it like a stack lift on a normal HP calc, so the number is copied (actually added to) “y” and stored there. The changing of the display does affect the display register (aka the “x” register), which IS different than a normal HP calculator, but it doesn’t affect the “y” register (the summation register) so by the time you actually add something you’re back in fix 3 mode and the addition acts as if there wasn’t any intermediate rounding.
I’m not sure if this is “expected” behavior, but at least I understand it now.-kby