In less than two decades the electronic digital computer has evolved from a high-speed replacement for the abacus to a full-fledged partner in dialogue with humans. By its very nature, on-line computing thrusts the user into an entirely different environment than does conventional batch processing. The problems inherent in a person's being made a system component---in a sense an extension of the computer hardware---were largely ignored until quite recently. Since the early users of on-line systems were highly skilled professionals who were both willing and able to communicate in terms most convenient for the machine, few programmers were aware of the user-computer communications gap, and even fewer were concerned about it. However, the lowered cost of computer access and the proliferation of on-line systems produced a new breed of users, people whose expertise was in some area other than computer technology. As their initial fascination with conversational computing wore off, users reported experiencing feelings of intense frustration and of being "manipulated" by a seemingly unyielding, rigid, intolerant dialogue partner, and these users began disconnecting from time-sharing services at a rate which was very alarming to the industry.