GetAspectRatio procedure

  DECLARATION:  GetAspectRatio(var Xasp, Yasp : Word)

      PURPOSE:  Returns the effective resolution of the graphic screen
                from which the aspect ratio can be computed.

         UNIT:  Graph

      REMARKS:  Each graphics mode and driver has an associated aspect ratio
                (maximum Y resolution divided by maximum X resolution). This
                ratio can be computed by dividing the first parameter, Xasp
                by the second, Yasp.  This value can be used to make arcs,
                circles, and pie slices round.

 RESTRICTIONS:  Must be in graphics mode.