The word input is used as a noun (information received or the process of receiving it) and less often as a verb (to receive information; or to enter information that a program then uses as input).
Computers commonly use keyboards and mice to receive input from users. Other input comes from networks and storage devices such as disk drives.
In control theory, the inputs of a system are the signals that can be observed or affected that feed into the system. Specifically, inputs are differentiated from states
An Input Iterator is an iterator that may be dereferenced to refer to some object, and that may be incremented to obtain the next iterator in a sequence.
Input Iterators are not required to be mutable.
[4] It is not guaranteed that it is possible to pass through the same input iterator twice.