⤷ Get system decimal separator

Use GetLocaleInfo function with LOCALE_SDECIMAL parameter.

procedure TForm1.Button1Click(Sender: TObject);
var
  MyDecimal: PChar;
begin
  MyDecimal:=StrAlloc(10);
  GetLocaleInfo(
    LOCALE_SYSTEM_DEFAULT, 
    LOCALE_SDECIMAL, 
    MyDecimal, 
    10);
  Label1.Caption:='System decimal is - "'+MyDecimal+'"';
end;
More for developers