NAME:  ClearViewPort

     USE:  Procedure to clear the current viewport.  This procedure uses
           the color stored in palette(0) to clear the viewport. If
           any errors occur they will be returned in GraphResult.

     DEPENDENCY:  Must first be in graphics mode.  The unit Graph
                  must also be placed in the uses section.

     SYNTAX: ClearViewPort


     EXAMPLE: ClearViewPort;