Which programming language is used for making Windows 10?

See for example the source code that implements the familiar Registry, a kernel component known internally as the configuration manager, “Cm”, in of what runs in kernel mode is also written in the C programming language (most file systems, networking, most drivers…) with some C++ here and there. The full source tree with all the code, test code and everything that together constitutes the “Windows source code” is more than a half terabyte in size, in more than 4 million files. Below is a screenshot which may or may not depict statistics about a full Windows enlistment (source code, test files, build tools, everything)

One one occasion, I left a Git branch stall for a few weeks and, when I got back to it, it was behind by almost 60,000 commits.

Source: www.quora.com