Open Sourcing Windows Calculator

As developers, if you would like to know how different parts of the Calculator app work, easily integrate Calculator logic or UI into your own applications, or contribute directly to something that ships in Windows, now you can. In addition to reusing and adapting the code in your own apps, anyone can participate in the development of Windows Calculator. To make this even easier, we will be contributing custom controls and API extensions that we use in Calculator and other apps, to projects like the Windows Community Toolkit and the Windows UI Library.

Source: blogs.windows.com