C++ How to Program, 10/e

13.2 Streams

C++ I/O occurs in streams, which are sequences of bytes. In input operations, the bytes flow from a device (e.g., a keyboard, a disk drive, a network connection) to main memory. In output operations, bytes flow from main memory to a device (e.g., a display screen, a printer, a disk drive, a network connection).

An application associates meaning with bytes. The bytes could represent characters, raw data, graphics images, digital speech, digital music, digital video or any other information an application may require. The system I/O mechanisms should transfer bytes from devices to memory (and vice versa) reliably. The time these transfers take typically is far greater than the time the processor requires to manipulate data internally. ...