Answer:The interface is the means by which a user communicates with a system, whether to get it to perform some function or computation directly (e.g., compute a trajectory, change a word in a text file, display a video); to find and deliver information (e.g., getting a paper from the Web or information from a database); or to provide ways of interacting with other people (e.g., participate in a chat group, send e-mail, jointly edit a document). As a communications vehicle, interfaces can be assessed and compared in terms of three key dimensions: (1) the language(s) they use, (2) the ways in which they allow users to say things in the language(s), and (3) the surface(s) or device(s) used to produce output (or register input) expressions of the language. The design and implementation of an interface entail choosing (or designing) the language for communication, specifying the ways in which users may express ''statements" of that language (e.g., by typing words or by pointing at icons), and selecting device(s) that allow communication to be realized-the input/output devices.
Box 3.1 gives some examples of choices at each of these levels. Although the selection and integration of input/output devices will generally involve hardware concerns (e.g., choices among keyboard, mouse, drawing surfaces, sensor-equipped apparel), decisions about the language definition and means of expression affect interpretation processes that are largely treated in software. The rest of this section briefly describes each of the dimensions and then examines how they can be used
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