What our teachers don't tell us in school is that we will spend most of our scientific or engineering career in front of computers, trying to beat them into submission. My formal training in computational science is nil, which I suspect is true of 90 percent of the scientists and engineers in the world. In this book, I attempt to bring together in one place the very basic facts that every technical person should know about computers. The computers of today still require you to know quite a bit about them in order to use them effectively for technical data analysis. Scientists and engineers who are computer novices should read this book cover to cover (that is, in my modest opinion). Experienced computer users should use this book as a reference. There are nuggets of useful information in this book waiting to be discovered by even the most computer-literate of you. Changes in the Second Edition Numerous corrections and clarifications were made throughout the text. Thanks to all of you who sent in your comments on the first edition. In addition, the index and glossary have been greatly improved.