Standard C++ does not directly address the issue of multiprocessing, threads, and thread safety. This issue is implementation dependent, which enables vendors to decide whether or not to provide multithreading support for a specific environment. It is important to note, however, that nothing in the Standard Library or the language itself disallows multithreading and thread safety. Thus, in a multithreaded environment, exception handling for example, should be thread safe, whereas a single threaded environment (such as DOS) may implement exception handling in a manner that is not thread safe.