procedure TForm1.Button1Click(Sender: TObject);
var
  f: file;
  i: integer;
begin
  i := 10;
  AssignFile(f, 'C:\DownLoad\Test.Bin');
  ReWrite(f, 1);
  BlockWrite(f, i, sizeof(i));
  FlushFileBuffers(TFileRec(f).Handle);
  CloseFile(f);
end;