In older stages of C++, the ios::nocreate and ios::noreplace open modes were part of the <fsteam.h> family of classes. However, the revised <fstream> family of file manipulation classes, which should be used instead of the now deprecated <fstream.h>, does not recognize these flags anymore. What happened to them?
Along with the templatization of the <fstream> classes, the C++ standardization committee decided to remove from std::ios_base (which now replaces ios) the open mode flags that were considered too platform-specific, including ios_base::nocreate and ios_base::noreplace. Programmers who migrate from <fstream.h> to <fstream> may find that their code refuses to compile because it uses these disused open mode flags. The alternative is either to use platform specific APIs or use alternative coding conventions that do not rely on these flags.