It is easy to read about computers 'sending messages' or "giving orders' without really knowing what this really means. One of the goals of this paper will be to remedy this by giving the reader a background in the kinds of representations that computer programs have and what they do with them. There is, however, a larger reason for looking at program "conversations": programs can give us a special window on what it means to communicate, a model against which we can compare our own communication, since, unlike people, programs can be examined as closely as we like and dissected and modified for experiments.