High efficiency, large scale, stationary computing systems – supercomputers and data centers – are becoming increasingly important due to the movement of data storage and processing onto remote cloud servers. This book is dedicated to a technology particularly appropriate for this application – superconductive electronics, in particular, rapid single flux quantum circuits. The primary purpose of this book is to introduce and systematize recent developments in superconductive electronics into a cohesive whole to support the further development of large scale computing systems.