A basic introduction to the field of digital systems, offering broad coverage of the fundamental concepts of switching circuit theory. The first 2 chapters provide an introduction to switching devices and to number systems and codes. Chapters 3 and 4, on combinational switching circuits, present Boolean algebra by abstracting physical behavior of devices into mathematical symbolism and discuss the problem of simplifying switching functions. Chapters 5 and 6 provide parallel integrated discussions of sequential circuits with pulse inputs and sequential circuits with level inputs. The concluding chapter considers the effects of spurious delays on switching circuits.