C++

6.2    Streams

You have seen streams in examples many times, but rarely did their type appear because we used the predefined streams of the standard library:

• std::cout of type std::ostream is used for standard output, usually to the console—that is, the screen. Or you can redirect the output to a file.

• std::cin of type std::istream is used for standard input, usually from the keyboard or a redirected file.

• std::cerr and std::clog are also output data streams of type std::ostream and usually end up on the screen, but you can redirect them to a file separately from std::cout.

For inputs and outputs of a normal program flow, you normally use std::cin and std::cout. Each output takes time, and a call has overhead, so std::cout is buffered: ...