unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Edit1: TEdit;
    procedure Edit1Change(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Edit1Change(Sender: TObject);
begin
   Edit1.Text:='';   //点击一下edit为空
end;

procedure TForm1.Button1Click(Sender: TObject);
var
     temp: Integer;  //定义整数temp
begin
     temp:=strtoint(Edit1.Text);   //edit文本都是
     Label1.Caption:=inttostr(temp mod 10);
     Label1.Visible:=True;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
     temp: Integer;
begin
     temp:=strtoint(Edit1.Text);
     Label2.Caption:=inttostr(temp div 10 mod 10);
     Label2.Visible:=True;
end;

procedure TForm1.Button3Click(Sender: TObject);
var
     temp: Integer;
begin
     temp:=strtoint(Edit1.Text);
     Label3.Caption:=inttostr(temp div 100 mod 10);
     Label3.Visible:=True;
end;

procedure TForm1.Button4Click(Sender: TObject);
var
     temp: Integer;
begin
     temp:=strtoint(Edit1.Text);
     Label4.Caption:=inttostr(temp div 1000 mod 10);
     Label4.Visible:=True;
end;

end.

 方框如下：

 运行结果如下：