The title of this talk is deliberately misleading: I really want to talk about misinformation.. Most citizens in what we laughingly call an "information society" derive most of what they know about their world from the mass media, for example from television, newspapers, more recently and increasingly from the World Wide Web and other such sources. But while it is true that the content of the mass media as a whole is from 90 to 95% trash, it is a mistake to blame the media establishment alone for the peoples' miserable state of world knowledge.Where, after all, is information created, where does it come from? The media delivers not "news", not "information", it delivers messages (signals) that, in order to produce information, must first be converted by the work of interpretation. That labor can be done only by (in the present context) the human mind.Information = interpretation ( signals ).Information theory teaches that messages have no information content, their interpretation does. And, what is most important, an interpretation of a message is a function of the state (or, in other words, the expectations) of the receiver! It follows that understanding a message, say the "news" delivered on television, involves the existing state of knowledge of the viewer, hence his or her education, socialization, indeed, in principle his whole life history.For us as educators, also as computer scientists, this implies that we must be attentive to the "state of the receiver". We must be attentive to the forces that influence the ability of our students to make sense of the signals they receive from us, from the media and from the rest of their world. We must teach them to think critically, and this foremost by means of our own example.

There are two distinct (though not necessarily disjoint) types of language extension. The first is a syntactic extension, in which the class of expressions interpretable within a language is widened. The second is an extension of the functional domain in which operations not previously performable are added to the language. These extensions may be implemented by completely reprogramming the basic language processor (the compiler or interpreter), but such extensions may often be achieved at far less cost by embedding. The authors give an example of each of these two types of extensions by embedding, adding list-processing facilities to the FORTRAN language, and extending the list processing language LISP to facilitate expression and interpretation of string transformations. As an aid to those unfamiliar with list processing, there is a section which reviews this subject. Included are descriptions and explanations of list structures, the various notations used for lists, the basic processes of list processing, and the different notations (machine language, functional, and prototype) used for expressing processing of lists.