17.5.1. Formatted Input and Output
In addition to its condition state (§ 8.1.2, p. 312), each
iostream object also maintains a format state that controls the details of how IO is formatted. The format state controls aspects of formatting such as the notational base for integral values, the precision of floating-point values, the width of an output element, and so on.
The library defines a set of manipulators (§ 1.2, p. 7), listed in Tables 17.17 (p. 757) and 17.18 (p. 760), that modify the format state of a stream. A manipulator is a function or object that affects the state of a stream and can be used as an operand to an input or output operator. Like the input and output operators, a manipulator returns the stream object to which it is applied, ...