Foreword [to Special Issue]

The Technical Committee on Mathematical Foundations of Computing, IEEE Computer So ciety, held its twentieth annual symposium on October 29-31, 1979, in San Juan, Puerto Rico. In order to celebrate this twentieth anniversary, it was decid ed to add a special fea ture to the symposium. Three distinguished scient ists were invited to present personal histories of their involvement in the development of the foundations of computer science and to provide perspective on some of the themes that emerged in the early days and that have greatly influenced the field. Sheila A. Gr eibach spoke on "Formal Languages: Origins and Directions," Juris Hartmanis presented "Observations About the Development of Theoretical Computer Science," and Stephen C. Kleene spoke on "Origins of Recursive Function Theory." This special issue presents revised versions of the texts of these three lec tures (the papers have been refereed).