The relentless growth of the computer industry over more than 30 years has been driven on by a series of major innovations. High-level languages; solid-state logic; compatible machine ranges; disk storage; time-sharing; data communications; virtual machine architectures; the use of LSI and solid-state memory; text processing; personal computers; sucessful packaged software; each advance in its turn has opened up new markets and set off a new spurt of expansion. A vital conclusion of this study is that expert systems promise to be another such major innovation.