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.