Как изменить сразу все одним циклом?

BitBtn3.Caption:='X';
BitBtn4.Caption:='X';
BitBtn5.Caption:='X';
BitBtn6.Caption:='X';
BitBtn7.Caption:='X';
BitBtn8.Caption:='X';
BitBtn9.Caption:='X';
BitBtn10.Caption:='X';

var i:Integer
For i:=3 to 10 do
begin
BitBtn[i].Caption:='X';
end;

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;
 
type
  TForm1 = class(TForm)
    btnStep: TButton;
    btnReset: TButton;
    Image1: TImage;
    Label1: TLabel;
    procedure FormCreate(Sender: TObject);
    procedure btnStepClick(Sender: TObject);
    procedure btnResetClick(Sender: TObject);
  private
    { Private declarations }
    a: array[0..255] of integer;
    cnt: integer;
    procedure ShowArray;
    procedure AddValue(aValue: integer);
    procedure Reset;
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
function GetCPUClock: double;
var
  Freq, Counter: Int64;
begin
  QueryPerformanceFrequency(Freq);
  QueryPerformanceCounter(Counter);
  Result := Counter / Freq;
end;
 
function GetCPUClocki64: Int64;
begin
  QueryPerformanceCounter(Result);
end;
 
procedure TForm1.FormCreate(Sender: TObject);
begin
  Image1.Picture.Bitmap.Width  := 100;
  Image1.Picture.Bitmap.Height := 256;
  Image1.Picture.Bitmap.PixelFormat := pf32bit;
  Image1.AutoSize := true;
 
  Reset;
  ShowArray;
end;
 
procedure TForm1.btnStepClick(Sender: TObject);
begin
  AddValue(GetCPUClocki64 mod 100);
  ShowArray;
end;
 
procedure TForm1.btnResetClick(Sender: TObject);
begin
  Reset;
  ShowArray;
end;
 
procedure TForm1.ShowArray;
var
  i: integer;
begin
  with Image1.Picture.Bitmap do
  begin
    Canvas.FillRect(Rect(0, 0, Width, Height));
    for i := 0 to High(a) do
    begin
      Canvas.MoveTo(i, 255);
      Canvas.LineTo(i, 255-a[i]);
    end;
  end;
  Label1.Caption := IntToStr(cnt);
end;
 
procedure TForm1.AddValue(aValue: integer);
begin
  if (aValue >= 0) and (aValue <= High(a)) then
    a[aValue] := a[aValue] + 1;
  Inc(cnt);
end;
 
procedure TForm1.Reset;
var
  i: integer;
begin
  for i := 0 to High(a) do
    a[i] := 0;
  cnt := 0;
end;
 
end.