We describe the hardware and software aspects of an automatic spectroscopy system based upon a programmable calculator and a prism monochromator. Linear spectral presentation is obtained by a four-point Aitken-Lagrange interpolation performed at each data point. The interpolation subroutine, which is also useful for data logging with thermocouples, is described in detail. Both open- and closed-loop applications of the system to reflectance and modulation spectroscopies are discussed, and additional uses are suggested.