(GET-DRIVER-NAME)

Returns the name of the currently loaded driver, without path and without its ".BGI" extension. When no driver is loaded, returns "". Can be used to know if a call to INIT-GRAPH is necessary or not. A good startup code would be:
(if (= (GET-DRIVER-NAME) "")
    (INIT-GRAPH)
    (SET-GRAPH-MODE))
Thus you can abort your program as often as you want, and restart it without filling the memory with copies of the graphics driver.