Logic and the development of programming languages, 1930-1975

Compared with the history' of computing hardware, the history of software is in a relatively unde veloped state. In particular, the history of programming languages still consists for the most part of technical accounts presenting a rather Whiggish perspective on developments. Given the importance of software in the contemporary world, however, it is important to develop a more sophisticated un derstanding of the medium in which it is expressed. This thesis considers some aspects of this history with the aim of examining the influence of formal logic on the evolution of notations for expressing computer programs. It is argued that this was not a natural or inev itable application of theory to practice, as is sometimes suggested, but a complex and contingent process with a rich history of its own. Two introductory chapters discuss the work on computability carried out by logicians in the mid-1930s. and the controversial topic of the role of logic in the invention of the computer. The body of the thesis proceeds chronologically, considering machine codes, the introduction of higher level notations, structured progTamrning and software engineering, and the early object-oriented languages. The picture that emerges is that formal logic was deliberately employed by programming lan guage designers to provide a model for a theoretical understanding of programming languages and the process of program development. This led to a flourishing research programme in the 1960s and 1970s, many of whose results are of lasting significance and value. The thesis concludes by exam ining the early history of object-oriented languages, arguing that this episode shows the emergence of limits to the applicability of the logical research programme