Standard output stream
cout is an object of class ostream that represents the standard output stream. It corresponds to the cstdio stream stdout.
By default, most systems have their standard output set to the console, where text messages are shown, although this can generally be redirected.
Because cout is an object of class ostream, we can write characters to it either as formatted data using for example the insertion operator (ostream::operator<<) or as unformatted data using the write member function, among others (see ostream).
|cin|| Standard input stream (object)|
|cerr|| Standard output stream for errors (object)|
|clog|| Standard output stream for logging (object)|