This book is a comprehensive introduction to the science and art of designing digital circuits. It begins by describing two foundational topics, numbers systems and boolean algebra. These topics then form the basis for the introduction of simple combinational circuits, or circuits without a memory. Complex circuits of this form are then described. It is shown, for example, how to construct a carry-look-ahead adder from elementary logic gates. Sequential digital circuits, or circuits with memories, are then treated, with the emphasis on sequential design. These topics then allow the introduction of a simple but operational digital computer that includes an arithmetic logic unit (ALU). The book concludes by showing that many of the principles developed in earlier chapters can be applied to the construction of intelligent machines.