In the 10 years since the first commercially available microprocessor was announced, nearly all commercial optical and infrared spectrometers have become computer-controlled. The advantages of such control and the cost of writing the necessary programs are discussed, and the industrial and academic situations contrasted. Data handling is discussed in terms of signal handling and the subsequent data-processing techniques available. Examples are given of the use of methods to aid visualization. Results are given of the application of the least-squares method to the measurement of a trace component, and an infrared interpretative search program is described.