Windows is not POSIX compliant, but there are many attempts to make it so. There are open source initiatives such as Cygwin and MinGW that provide a less POSIX-compliant development environment, and support C applications using the Microsoft Visual C runtime library. Microsoft itself has made some attempts at POSIX compatibility, such as the Microsoft POSIX subsystem. The latest compatibility layer made by Microsoft is the Windows Linux Subsystem, which is an optional feature that can be activated in Windows 10 and has been well received by developers (including myself).