Windows API and the entirety of its client code aren't a good source of standard C programming. On the source level you have additional types and qualifiers/ann

Windows API and the entirety of its client code aren't a good source of standard C programming. On the source level you have additional types and qualifiers/annotations that only MSVC understands. LLM copilot doesn't really understand the context of the project, it just goes for similar text. So if you train on big projects you're picking up their patterns only. When a copilot user asks for a string concatenation 'tip' you want LLM to output a general answer, not something tied to a specific project. Big project is likely to use abstraction over strings, where base library usage is shrunk down to few lines of code as opposed to abstraction. In this case you'd want LLM to source a few "simpler" projects that use base library strings abundantly, so it can have decent amount of text for the most likely correct match over user's input. I do believe Microsoft has all the code available for good training, it's not only about Azure, Windows and Office, there is tons more and it's open source already.