The Waite Group's C++ Primer Plus, Third Edition

Input with cin

Now it's time to turn to input and getting data into a program. The cin object represents the standard input as a stream of bytes. Normally, you generate that stream of characters at the keyboard. If you type the character sequence 1998, the cin object extracts those characters from the input stream. You may intend that input to be part of a string, to be an int value, to be a float value, or to be some other type. Thus extraction also involves type conversion. The cin object, guided by the type of variable designated to receive the value, must use its methods to convert that character sequence into the intended type of value.

Typically, you use cin as follows:

cin >> value_holder;

Here value_holder identifies the memory location ...