Microsoft has fixed a decade-old issue in the Windows Calculator, according to a report by Softpedia. This bug has been around for many years, and one report was posted on Microsoft’s Community forums in 2010 when the current version of Windows was Windows 7. Given that the library used by the Calculator didn’t change, the bug is still there in Windows 8.1 and Windows 10.
Windows 10 Redstone 5 build 17639 is the one bringing this bugfix and this bug was reported as the issue is known as the “square root of perfect square” bug, and resulted in incorrect answers in certain situation.
For Example: Calculating the square root of 4, then subtracting 2 and the answer should be 0, but the Windows Calculator sometimes gives the wrong answer, due to what Microsoft claims to be arbitrary precision arithmetic library”.