This book develops techniques for simulating digital logic circuits in Microsoft's Excel that provide a useful tool to both the student and the practicing engineer. It introduces the subject by showing how logic devices, taken from the standard 7400 family, can be modeled and stored in a library. These functions can then be combined by the user as building blocks to design more complex circuits, both combinatorial and sequential. The simulations not only allow the designs to be verified to ensure they provide expected outputs and states, but can also perform detailed timing analysis. Worst case timing conditions can be imposed to stress the circuits so that the resultant behavior can be observed. Methods showing how the user can add additional devices to the simulation library are also covered.