What is the contemporary computer’s fundamental structure? How does it function? How has it been feasible to fit more and more compact devices with such a large amount of power? What will the upcoming computer generations look like? In this Very Short Introduction, Darrel Ince examines the fundamental ideas that underlie all computers, the hardware and software advancements that made them so compact and widely used, the problems that the computer revolution created, particularly brand-new forms of cybercrime and security concerns, the Internet and the emergence of “cloud computing,” and the promise of completely new vistas that quantum computing and computing with DNA hold.