델파이 계산기를 만드는데요... 모드랑 제곱 추가를 어떻게 해야할지를 모르겠습니다..제가 여기까지는 만들었는데 추가를 어떻게 해야 할까요?...

unit SG;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, FMX.StdCtrls,
  FMX.Edit, FMX.Layouts;

type
  TMcal = class(TForm)
    Layout1: TLayout;
    Edit1: TEdit;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    Button6: TButton;
    Button7: TButton;
    Button8: TButton;
    Button9: TButton;
    Button10: TButton;
    Button11: TButton;
    Button12: TButton;
    Button13: TButton;
    Button14: TButton;
    Button15: TButton;
    Button16: TButton;
    Button17: TButton;
    Button18: TButton;
    Button19: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
    procedure Button6Click(Sender: TObject);
    procedure Button7Click(Sender: TObject);
    procedure Button8Click(Sender: TObject);
    procedure Button9Click(Sender: TObject);
    procedure Button10Click(Sender: TObject);
    procedure Button15Click(Sender: TObject);
    procedure Button11Click(Sender: TObject);
    procedure Button12Click(Sender: TObject);
    procedure Button13Click(Sender: TObject);
    procedure Button14Click(Sender: TObject);
    procedure Button17Click(Sender: TObject);
    procedure Button16Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Mcal: TMcal;
  val1,val2:real;
  operation:string;

implementation

{$R *.fmx}

procedure TMcal.Button10Click(Sender: TObject);
begin
edit1.Text:= Edit1.Text + '0'
end;

procedure TMcal.Button11Click(Sender: TObject);
begin
val1:= StrToFloat (edit1.Text);
operation:='+';
edit1.Text:=''
end;

procedure TMcal.Button12Click(Sender: TObject);
begin
val1:= StrToFloat (edit1.Text);
operation:='-';
edit1.Text:=''
end;

procedure TMcal.Button13Click(Sender: TObject);
begin
val1:= strTofloat (edit1.Text);
operation:='*';
edit1.Text:=''
end;

procedure TMcal.Button14Click(Sender: TObject);
begin
val1:= strtofloat (edit1.Text);
operation:='/';
edit1.Text:=''
end;

procedure TMcal.Button15Click(Sender: TObject);
begin
edit1.Text:= Edit1.Text + '.'
end;

procedure TMcal.Button16Click(Sender: TObject);
begin
edit1.ClearSelection;
val1:=0;
val2:=0;
edit1.SetFocus;
end;

procedure TMcal.Button17Click(Sender: TObject);
begin
val2:= strToFloat (edit1.text);
if operation='+' then edit1.Text:=FloatToStr (val1+val2);
if operation='-' then edit1.Text:=FloatToStr (val1-val2);
if operation='*' then edit1.Text:=FloatToStr (val1*val2);
if operation='/' then edit1.Text:=FloatToStr (val1/val2);
end;

procedure TMcal.Button1Click(Sender: TObject);
begin
     edit1.Text:= Edit1.Text + '1'
end;

procedure TMcal.Button2Click(Sender: TObject);
begin
      edit1.Text:= Edit1.Text + '2'
end;

procedure TMcal.Button3Click(Sender: TObject);
begin
        edit1.Text:= Edit1.Text + '3'
end;

procedure TMcal.Button4Click(Sender: TObject);
begin
      edit1.Text:= Edit1.Text + '4'
end;

procedure TMcal.Button5Click(Sender: TObject);
begin
edit1.Text:= Edit1.Text + '5'
end;

procedure TMcal.Button6Click(Sender: TObject);
begin
edit1.Text:= Edit1.Text + '6'
end;

procedure TMcal.Button7Click(Sender: TObject);
begin
edit1.Text:= Edit1.Text + '7'
end;

procedure TMcal.Button8Click(Sender: TObject);
begin
edit1.Text:= Edit1.Text + '8'
end;

procedure TMcal.Button9Click(Sender: TObject);
begin
edit1.Text:= Edit1.Text + '9'
end;

end.