What is the basic nature of the modern computer? How does it work? How has it been possible to squeeze so much power into increasingly smaller machines? What will the next generations of computers look like? In this Very Short Introduction, Darrel Ince looks at the basic concepts behind all computers, the changes in hardware and software that allowed computers to become so small and commonplace, the challenges produced by the computer revolution--especially whole new modes of cybercrime and security issues, the Internet and the advent of "cloud computing," and the promise of whole new horizons opening up with quantum computing and computing using DNA.