The last decade has seen an enormous change in the capability of information technology and also in the expectations of what that technology can provide. The personal computer revolution at the start of the 1980s brought computing power to the desktop in a way that, for the first time, non-technical users could understand and use in their everyday work. The invisible wall of mystique that had separated computers from their potential users for so long had been demolished, and the world of business would never be the same again. As we entered the 1990s, a decade later, we witnessed the beginnings of another revolution. This revolution is not so obvious, but its implications are even more far-reaching. It is not so obvious because it is happening behind the scenes, in the communications and computing infrastructure that support the machines that can be seen sitting on office desks and, increasingly, being carried with business people as standard equipment along with a briefcase and umbrella. It is potentially more far-reaching for the following reason. The per­ sonal computer of the 1980s brought computing power to the user in a box that could fit on a desk. The revolution of the 1990s brings to the user computing power that is distributed across the whole planet.