Microsoft Fixes Decade-Old Windows Calculator Square Root Bug
Microsoft has finally fixed a decade-old issue in the Windows Calculator that’s widely known as the “square root of perfect square” bug causing incorrect results for certain operations.
Windows 10 Redstone 5 build 17639, which is available at this point for members of the Windows Insider program enrolled in the Skip Ahead ring, is the one bringing this bugfix, with everyone else to get it either when work on the next Windows 10 feature release completes or in the meantime with a Calculator app update.
Specifically, if you want to replicate the bug, launch the Calculator app and try to calculate the square root of 4 and then subtract 2. While the answer should be 0, the Windows Calculator sometimes gives the wrong answer due to what Microsoft claims to be arbitrary precision arithmetic library.