The role of an input in a computer system is to provide data for further processing.
An input consists of data or commands that are entered into the computer system usually via an input device such as a keyboard, mouse, OMR, barcode reader, scanner etc.
The input data is converted into digital data that can be dealt with by the computer.
Sometimes the input is already in digtial format, for example when it has been transmitted from another computer but most of the time it needs to be converted into a digital format before processing can take place.