In the past twenty years, computing power has been increasing at an exponential rate. During that period speeds of high performance computers have increased from just over one megaflops (million floating point operations per second) to almost one gigaflops (billion floating point operations per second). Computer memory has shown a similar increase: around a million words twenty years ago and now rapidly approaching a billion words. In computational science a word usually refers to a 64 bit quantity. Thus a million words is 8 megabytes (MB) and a billion words is 8 gigabytes (GB).
The increase in computing power available on our desktops has been even more dramatic. Twenty years ago, virtually all scientific computation was performed on a mainframe. Then, the standard mode of operation was batch and card decks were more common than computer terminals. Today, the computing power of an average PC exceeds that of most mainframes of twenty years ago. Moreover, the computing power of the PC has increased by an order of magnitude about every four years since its introduction in 1982.