Semiotics studies systems of signs. It regards all sign systems as the product of a single human faculty for creating order. The distinction it provides, of signifier, sign and signified, can give a more sophisticated and incisive way of differentiating aspects of the sign than can be derived from any other known source. Information science would seem to have some unnoticed affinities with semiotics in its concerns with the retrieval and transmission of material products of the semiotic faculty and with meaning to concept relations. The alignment of information science with the physical sciences and technology has been criticised and its disciplinary identity questioned. Information science would seem to derive what identity it has from a widely shared concern with computer based retrieval of documentary information. However, a unifying principle for the document and the computer has not been enunciated. For semiotics, written language, and computer programs can be comprehended within the analytical category of the signifier. Automata theory regards the computer as a universal information machine and replaces ideas of energy and motion by logical operations. At the level of discourse of logical operations, there is no distinction between a written expression, or program, and the particular information machine specified by that written expression. Elements in linguistics, not registered in the literature of information science, have departed from the received position that written language is simply a representation of speech and have preferred to regard it as an autonomous system of signs. A specific unifying principle for the document and the computer is then the presence of writing. Revealing such a unifying principle indicates that semiotics can clarify significant issues within the established domains of information science.