std::cout, std::wcout

The global objects std::cout and std::wcout control output to a stream buffer of implementation-defined type (derived from std::streambuf), associated with the standard C output stream stdout.

These objects are guaranteed to be initialized during or before the first time an object of type std::ios_base::Init is constructed and are available for use in the constructors and destructors of static objects with ordered initialization (as long as <iostream> is included before the object is defined).

Unless std::ios_base::sync_with_stdio(false) has been issued, it is safe to concurrently access these objects from multiple threads for both formatted and unformatted output.

By specification of std::cin, std::cin.tie() returns &std::cout. This means that any input operation on std::cin executes std::cout.flush() (via std::basic_istream::sentry's constructor). Similarly, std::wcin.tie() returns &std::wcout.

By specification of std::cerr, std::cerr.tie() returns &std::cout. This means that any output operation on std::cerr executes std::cout.flush() (via