GPSS configuration files turn certain features on and off, set up initial values for running, and the like.
Information on a few of these files is open. Some of these need only the existence of the file name to be operational - that is, there doesn't have to be anything in the file itself.
GPSS.CFG (adding your home location)
METRIC.CFG (moving about in kilometers and meters, instead of miles and feet)
DIALS.CFG (automatically turning instruments on when GPSS begins)
SOUNDS.CFG (controls whether GPSS talks to you and if so, how often)