Computer controlled X-ray spectrometers have been available since the mid 1950's and there are many hundreds of these systems in use today. The degree of sophistication of these machines has increased gradually over the past several years, but in all cases the flexibility of the analytical system is directly relatable to the available computer hardware. In the design of any computer controlled X-ray spectrometer, it is highly desirable to keep the cost of the computer, plus its associated interfaces and software, to within a reasonable fraction of the total cost of the whole system. A figure of perhaps 30% or so is a good figure to aim for in this context. A compromise must, therefore, always be sought between cost and computational power--which generally means flexibility.