Hi Calc | Classic retro game for the Commodore PET Computer (1971)

HI CALC is a high-precision calculator that can handle 120 significant figures on an 8K PET, and 684 on a 16K PET. I played around with this one for a little while, and I'm impressed. The program streamlines its internal representation of numbers by storing them in base 1000 (essentially 3-digit chunks). I tried multiplying two reasonably long numbers, equivalent to 2^64 * 2^128 (see screenshot), and verified that the answer was correct with WolframAlpha. The PET came back with this 58-digit answer pretty quickly, too. These days, we have modern tools available for this kind of calculation, but this program's still fun to play around with for a bit. It might even be worth studying how the program is put together for anyone interested in low-level arithmetic algorithms.