PROGRAM mouse
DO
   ! return current x and y window coordinates and state of mouse
   GET MOUSE x,y,s
   IF s = 1 then
      PRINT "button down",x,y
   ELSE IF s = 2 then
      PRINT "button clicked",x,y
   ELSE IF s = 3 then
      PRINT "button released",x,y
   END IF
LOOP
END