A program used to guide a user through a series of action that will help the user with some problem. For instance, if a users printer doesn't print, a troubleshooter could suggest that he examined if there is paper in the tray or if the plug is plugged in. Comprehensive troubleshooting theory has been developed. The basic objective is to minimize the average cost (time and/or money) to repair the fault. Bayesian Networks are sometimes used in troubleshooters to calculate the probabilities of each fault.