Windows NTFS and case sensitivity

Question

According to Wikipedia NTFS allows two similar names with different case (like Readme.txt vs. readme.txt) and it is only prevented by the windows file API.

Answer 1

NTFS is a case sensitive file system and treats files with the same name, but different case, as different files.

The Windows API presents an abstraction of NTFS that makes it appear as a case preserving file system, and it does this via the CreateFile API that almost all file creation and opening requests are routed through.

Namely, the case sensitivity of file opening or creation is mediated by the FILE_FLAG_POSIX_SEMANTICS flag passed to CreateFile.