Programming languages and system architectures are at the frontiers of two different worlds. The conference on which this book is based was an adventure in a land where the two worlds - the formal world of algorithms and the physical world of electronic circuits - interact. The participants explored this land under the guidance of internationally renowned researchers such as Butler W. Lampson, Susan Graham, Jan L.A. van de Snepscheut, and C.A.R. Hoare, all of whom gave invited papers. The volume includes these papers together with sixteen session papers. Subjects of special interest include: programing language design and history, programming environments, programming methods, operating systems, compiler construction, and innovative system architectures.