https://www.theverge.com/2019/3/6/18253474/microsoft-windows-calculator-open-source-github

Microsoft is making the source code for its Windows calculator available on GitHub today. The software maker wants to “build an even better user experience in partnership with the community.” Opening up the calculator means anyone can contribute code to improve the app, but Microsoft wants to evaluate prototypes of new features or user interface changes before the company starts implementing them or reviewing code.

The source code is now available on GitHub and it includes the build system, unit tests, and even the product road map for the calculator feature in Windows. While it might be a relatively minor part of Windows, the open-sourcing of the calculator follows years of Microsoft embracing open source. Microsoft even open-sourced the original File Manager from the ‘90s to allow it to run on Windows 10, and just recently made 60,000 patents open-source to help protect Linux.