1. Definitions and principles

The recent development of computing for the general public has been made possible not only by the falling cost of hardware, but above all by the maturing of human-computer interaction (HCI) techniques. Computer use is now within everyone's reach, whereas until the 1990s it seemed to be the preserve of specialists. Using a machine is becoming increasingly simple. But this simplicity is not innate, nor is it due solely to advances in hardware. It is the result of lengthy experimental efforts, and the price of a deep understanding of all the mechanisms involved in communication, particularly the associated cognitive mechanisms. It's up to the application designer to take into account the "human factors" that are responsible for the user's "comfort": communication must require as little effort as possible from the human, at the cost of extra work for the machine. Graphical user interfaces are...