An information system is an organisation of people, materials and machines that serves to facilitate the transfer of information from one person to another. Its function is social: to aid human communication. If we take this to mean all reception of signals by the human senses (sight, sound, small, touch, taste,...)- then communication is an incessant and essential accompaniment of all human activity. If we restrict the meaning of signals to flowing between people, much of the daily life of most of us is occupied by such interpersonal acts.

p. 1. - Information Systems (1973)