driver

driver n.  1. The {main loop} of an event-processing
   program; the code that gets commands and dispatches them for
   execution.  2. [techspeak] In `device driver', code designed to
   handle a particular peripheral device such as a magnetic disk or
   tape unit.  3. In the TeX world and the computerized typesetting
   world in general, a program that translates some device-independent
   or other common format to something a real device can actually
   understand.