Comment by canucker2016

Acording to https://en.wikipedia.org/wiki/Windows_Calculator#Windows_9x_..., the Win98 version of calc.exe got an arbitrary-precision math library for basic math functionality to fix this sort of problem.

also mentioned by Raymond Chen, https://devblogs.microsoft.com/oldnewthing/20040525-00/?p=39... :

"Today, Calc’s internal computations are done with infinite precision for basic operations (addition, subtraction, multiplication, division) and 32 digits of precision for advanced operations (square root, transcendental operators)."

And they fixed the square-root-of-a-perfect-square bug a few years ago, https://www.reddit.com/r/Windows10/comments/89s53g/microsoft...