l Ever since we published our Picture Book of Quantum Mechanics we have been asked to make available the programs we wrote to generate the computer graphics that illustrate the book. We have called the result INTERQUANTA (the Interactive Program of Quantum Mechanics), which we like to abbreviate further by IQ. This book is essentially an extensive user's guide for INTERQUANTA. The book also contains a short summary of the different subjects of quantum mechanics treated by IQ as well as a large number of exercises. The program can be used in two ways. By working through (at least a part of) these exer­ cises, the user of IQ explores a computer laboratory in quantum mechanics gaining experience in this abstract field by performing computer experiments. No knowledge of computer programming is required. The user only has to learn how to use some ofthe simple IQ commands and, in particular, the exten­ sive HELP facilities. A simpler way to use IQ is to study one or several of the ready-made demonstrations. In each demonstration the user is taken through one chapter of quantum mechanics. Short explanatory texts displayed on the screen interchange with graphics illustrating quantum-mechanical problems which are solved by the program.