Many of us want to understand how the technological instruments that so pervade modern society operate. This book answers questions about one of those devices: the scientific calculator. Calculator keys seem to work like magic. They tell us, for example, that the cosine of 56° is 0.559192903. This book explores the simple internal calculator processes (called algorithms or programs) that produce this and similar results. Although the text focuses on the calculator keys that compute powers, roots, logarithms, and trigonometry functions, insights are also provided into simple programming, conversion between decimal and binary numeration, and perhaps most important, the structure of our numeration systems. Many people think that the processes that drive calculators demand advanced mathematical concepts such as Taylor series. However, high school algebra and a minimum understanding of programming (provided by this text) supply enough background to understand these algorithms.