Text entry can also be seen as a task where different subtasks are shared between the human and the computer (Chapter 20).

Persons with varying capabilities and backgrounds need toeffectively enter text, or these systems fail as tools.

Text entry is also a good example of tool use (Chapter 19). A text entry method is a tool that allows the user to communicate with someone or something, typically other people or a service, using asynchronous text messages and longer documents.

The essence of dialogue is that communi-cation is organized in sequences of turns.

Interaction is understood as actions and reactions that minimize the discrepancybetween the present state and the goal state.

Informationtheory provides a rigorous formalism to understand and quantify interaction via the concept ofpassing messages through a noisy channel.

This con-cept, communication of information, is rooted in information theory (Chapter 17).

However, computers can also have goals or at least algorithmic objectives. This adds another levelto teleological determination.

One type of determination is shared by all theories of interaction in HCI: teleological determina-tion.