TOPIC 13.4.2
Ostream Class Objects

Cerr and clog are both objects of the ostream class and are set to the standard error device, which is usually the screen. The only difference in the two objects is outputs to cerr are not buffered and outputs to clog are buffered. This means that when using cerr the output is immediately seen on the screen while the output of clog could be held within a buffer for later examination.