This book provides an introduction to computer science, and shows how modem computer- based tools can be used in science, mathematics, and engineering. Computer-aided math- ematics has reached a level where it can support effectively many computations in science and engineering. In addition to treating traditional computer-science topics, an introductory book should show scientists and engineers how these computer-based tools can be used to do scientific computations. Students must get to know these possibilities, and they must gain practical experience. Learning a traditional programming language becomes less important, just as learning arithmetic is not a main topic of mathematics education. In an introductory book, it is clearly necessary to limit ourselves to a small part of the huge field of computer science. We emphasize topics that are related to possible applications in mathematics and the sciences. Technical and practical computer science have therefore been neglected.