사칙연산은 다 썼는데.....

소수점을 잘 모르겠네여..

제가 만든 소스는 이래여.

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Panel1: TPanel;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    Button6: TButton;
    Button7: TButton;
    Button9: TButton;
    Button10: TButton;
    Button11: TButton;
    Button12: TButton;
    Button13: TButton;
    Button14: TButton;
    Button15: TButton;
    Button16: TButton;
    Button17: TButton;
    Button18: TButton;
    Button19: TButton;
    Button20: TButton;
    Button8: TButton;
    procedure Button17Click(Sender: TObject);
    procedure Button13Click(Sender: TObject);
    procedure Button14Click(Sender: TObject);
    procedure Button15Click(Sender: TObject);
    procedure Button9Click(Sender: TObject);
    procedure Button10Click(Sender: TObject);
    procedure Button11Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
    procedure Button6Click(Sender: TObject);
    procedure Button7Click(Sender: TObject);
    procedure Button8Click(Sender: TObject);
    procedure Button12Click(Sender: TObject);
    procedure Button16Click(Sender: TObject);
    procedure Button20Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button19Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
 
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

  first : real;
  flag : smallint;
implementation

{$R *.DFM}


procedure TForm1.Button17Click(Sender: TObject);
begin
    edit1. text := edit1.text+'0';
    panel1.caption := panel1.caption+'0';
end;

procedure TForm1.Button13Click(Sender: TObject);
begin
    edit1. text := edit1.text+'1';
    panel1.caption := panel1.caption+'1';
end;

procedure TForm1.Button14Click(Sender: TObject);
begin
    edit1. text := edit1.text+'2';
    panel1.caption := panel1.caption+'2';
end;

procedure TForm1.Button15Click(Sender: TObject);
begin
     edit1. text := edit1.text+'3';
    panel1.caption := panel1.caption+'3';
end;

procedure TForm1.Button9Click(Sender: TObject);
begin
     edit1. text := edit1.text+'4';
    panel1.caption := panel1.caption+'4';
end;

procedure TForm1.Button10Click(Sender: TObject);
begin
    edit1. text := edit1.text+'5';
    panel1.caption := panel1.caption+'5';
end;

procedure TForm1.Button11Click(Sender: TObject);
begin
    edit1. text := edit1.text+'6';
    panel1.caption := panel1.caption+'6';
end;

procedure TForm1.Button5Click(Sender: TObject);
begin
     edit1. text := edit1.text+'7';
    panel1.caption := panel1.caption+'7';
end;

procedure TForm1.Button6Click(Sender: TObject);
begin
    edit1. text := edit1.text+'8';
    panel1.caption := panel1.caption+'8';
end;

procedure TForm1.Button7Click(Sender: TObject);
begin
    edit1. text := edit1.text+'9';
    panel1.caption := panel1.caption+'9';
end;

procedure TForm1.Button8Click(Sender: TObject);
begin
     first := strtofloat(edit1.text);
     edit1.clear;
     flag :=1;
     panel1.caption := panel1.caption+'/';
end;

procedure TForm1.Button12Click(Sender: TObject);
begin
     first := strtofloat(edit1.text);
     edit1.clear;
     flag :=2;
     panel1.caption := panel1.caption+'*';
end;

procedure TForm1.Button16Click(Sender: TObject);
begin
    first := strtofloat(edit1.text);
     edit1.clear;
     flag :=3;
     panel1.caption := panel1.caption+'-';
end;

procedure TForm1.Button20Click(Sender: TObject);
begin
   first := strtofloat(edit1.text);
     edit1.clear;
     flag :=4;
     panel1.caption := panel1.caption+'+';
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
    first := strtofloat(edit1.text);
     edit1.clear;
     flag :=5;
     panel1.caption := panel1.caption+'^';
end;

procedure TForm1.Button19Click(Sender: TObject);
begin
   case flag of
  1 : edit1.text := floattostr(first/strtofloat(edit1.text));
  2 : edit1.text := floattostr(first*strtofloat(edit1.text));
  3 : edit1.text := floattostr(first-strtofloat(edit1.text));
  4 : edit1.text := floattostr(first+strtofloat(edit1.text));
  5 : edit1.text := floattostr(power(first,strtofloat(edit1.text)));

  end;
end;
procedure TForm1.Button4Click(Sender: TObject);
begin
    edit1.clear;
    panel1.caption := '';
end;

end.

어느 부분에 변수 선언을 해주고, 어떻게 소수점 소스를 넣는지 알려주새여^^