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  VAR
      CheckSnow : Boolean;    { state of snow filtering }
 
  Unit:     Crt
 
  Context:  TextMode, Write, Writeln
 
  Description
 
    When CheckSnow is set to True, snow checking is performed when
    characters are stored in video memory. Older CGA systems sometimes
    show interference during scrolling and clearing the display. When
    snow checking is on, writing to video memory is performed only
    during horizontal retrace intervals. This clears the snow problem,
    but causes slower output.
 
    When CheckSnow is False, snow checking is disabled.
 
    Default setting is True. It is set whenever a color text mode is
    set. Ensure that snow checking is continuously disabled by setting
    CheckSnow to False after each TextMode call.
 
    CheckSnow has no effect when the variable DirectVideo, defined in
    the Crt unit, is set to False.