Describes a computer-controlled system capable of measuring a wide range of semiconductor resistivities and Hall coefficients, as well as their dependences upon temperature (4.2-600K), magnetic field (0-1.8 T), and monochromatic light irradiation (up to 2*1018 photons cm-2 s-1, held constant over the range 0.76-2.5 mu m). With the use of a guarded cable configuration, the response time for a 1013 Omega sample is less than 10 s. The system uses commercial components whenever possible and is built around a PDP 11-03 computer with a standard IEEE-488 I/O bus. The only important noncommercial piece of apparatus used is a wavelength scan and intensity control system for a popular, 1/4 m, high intensity monochromator.