This is implementation dependent. Check with your compiler's documentation.
For example, suppose you want to do binary
I/O using std::cin and std::cout.
Unfortunately there is no standard way to cause std::cin, std::cout, and/or
std::cerr to be opened in binary mode. Closing the streams and attempting to
reopen them in binary mode might have unexpected or undesirable results.
On systems where it makes a difference,
the implementation might provide a way to make them binary streams, but you
would have to check the implementation specifics
to find out.