From its first glimmerings in the 1950s, the software industry has evolved to become the fourth largest industrial sector of the US economy. Starting with a handful of software contractors who produced specialized programs for the few existing machines, the industry grew to include producers of corporate software packages and then makers of mass-market products and recreational software. This book tells the story of each of these types of firm, focusing on the products they developed, the business models they followed, and the markets they served.