A consideration of several different examples sheds new light on the problem of ereat-ing reliable, well-structured programs that behave efficiently. This study focuses largely on two issues: (a) improved syntax for iterations and error exits, making it possible to write a larger class of programs clearly and efficiently without go to state-

this paper is to refine this definition somewhat, adapting it to the purposes of the research community in computer science. Accordingly, we shall attempt to provide a reasonable definition of or, rather, criteria for folk theorems, followed by a detailed example illustrating the ideas. The latter endeavor might take one of two possible forms. We could take a piece of folklore and show that it is a theorem, or take a theorem and show that it is folklore. As an example of the first form we could have shown that the statement P NP, which is folklore, is also a theorem. However, since we have resolved to introduce no new technical material in this paper, and moreover, since researchers in our community seem to be less familiar with folklore than with theorems, Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission

Software engineering research and programming language design have enjoyed a symbiotic relationship, with traceable impacts since the 1970s, when these areas were first distinguished from one another. This report documents this relationship by focusing on several major features of current programming languages: data and procedural abstraction, types, concurrency, exceptions, and visual programming mechanisms. The influences are determined by tracing references in publications in both fields, obtaining oral histories from language designers delineating influences on them, and tracking cotemporal research trends and ideas as demonstrated by workshop topics, special issue publications, and invited talks in the two fields. In some cases there is conclusive This article has been developed under the auspices of the Impact Project. The aim of the project is to provide a scholarly study of the impact that software engineering research—both academic and industrial—has had upon practice. The principal output of the project is a series of individual papers covering the impact upon practice of research in several selected major areas of software