procedure TForm1.bt_lesenClick(Sender: TObject);

var nums : TStringList;
    i, current, ges, mid : integer;

begin
  nums := TStringList.Create;
  nums.LoadFromFile('nums.txt');
  ges := 0;

  for i := 0 to nums.Count-1 do
    begin
      current := current.Parse(nums[i]);
      ges := ges + current;
    end;

  mid := ges div nums.Count;
  lbl_mid.Caption := mid.ToString;
end;

procedure TForm1.bt_schreibenClick(Sender: TObject);

var nums : TStringList;
    i, cr : integer;

begin
  Randomize;
  nums := TStringList.Create;

  for i := 0 to 999 do
    begin
      cr := RandomRange(1, 101);
      nums.Add(cr.ToString);
    end;

  nums.SaveToFile('nums.txt');
end;