Procedure PositionCursor

    Updates VX and VY       : No
    Updates Cursor Position : Always

    This calls  the  BIOS  routine  to  move  the  cursor  to the current
    writing position on  the  screen.   For  example,  if  Cursor is True
    then this procedure is called after a GotoXY call.

    If  Cursor  is  False  then   although   the   writing  position  has
    moved (VX and VY), the  cursor  position is not updated so it flashes
    at the wrong area of the screen  (if  it  is visible).  You thus need
    to call  PositionCursor  manually  to  display the flashing cursor at
    the correct position.