Почти нормальный калькулятор

Unit Unit1;

interface

uses System, System.Drawing, System.Windows.Forms, LyceumLib;

type
  Form1 = class(Form)
    procedure Form1_Load(sender: Object; e: EventArgs);
    procedure Form1_Paint(sender: Object; e: PaintEventArgs);
    procedure button1_Click(sender: Object; e: EventArgs);
    procedure button2_Click(sender: Object; e: EventArgs);
    procedure button3_Click(sender: Object; e: EventArgs);
    procedure button4_Click(sender: Object; e: EventArgs);
    procedure button5_Click(sender: Object; e: EventArgs);
    procedure button6_Click(sender: Object; e: EventArgs);
    procedure button7_Click(sender: Object; e: EventArgs);
    procedure button8_Click(sender: Object; e: EventArgs);
    procedure button9_Click(sender: Object; e: EventArgs);
    procedure button10_Click(sender: Object; e: EventArgs);
    procedure button11_Click(sender: Object; e: EventArgs);
    procedure button12_Click(sender: Object; e: EventArgs);
    procedure button13_Click(sender: Object; e: EventArgs);
    procedure button14_Click(sender: Object; e: EventArgs);
    procedure button16_Click(sender: Object; e: EventArgs);
    procedure button15_Click(sender: Object; e: EventArgs);
    procedure textBox1_TextChanged(sender: Object; e: EventArgs);
  {$region FormDesigner}
  private
    {$resource Unit1.Form1.resources}
    button1: Button;
    button2: Button;
    button3: Button;
    button4: Button;
    button5: Button;
    button6: Button;
    button7: Button;
    button8: Button;
    button9: Button;
    button10: Button;
    button11: Button;
    button12: Button;
    button13: Button;
    button14: Button;
    button15: Button;
    button16: Button;
    label1: &Label;
    textBox1: TextBox;
    {$include Unit1.Form1.inc}
  {$endregion FormDesigner}
  public
    constructor;
    begin
      InitializeComponent;
    end;
  end;



var firstnum,secondnum,action:string;
var number1,number2:real;

implementation

procedure Form1.Form1_Paint(sender: Object; e: PaintEventArgs);
begin
end;

//1
procedure Form1.button1_Click(sender: Object; e: EventArgs);
begin
  var x1:string;
  x1:='1';
  textbox1.text:=textbox1.text+x1;
end;

//2
procedure Form1.button2_Click(sender: Object; e: EventArgs);
begin
  var x2:string;
  x2:='2';
  textbox1.text:=textbox1.text+x2;
end;

//3
procedure Form1.button3_Click(sender: Object; e: EventArgs);
begin
  var x3:string;
  x3:='3';
  textbox1.text:=textbox1.text+x3;
end;

//4
procedure Form1.button4_Click(sender: Object; e: EventArgs);
begin
  var x4:string;
  x4:='4';
  textbox1.text:=textbox1.text+x4;
end;

//5
procedure Form1.button5_Click(sender: Object; e: EventArgs);
begin
  var x5:string;
  x5:='5';
  textbox1.text:=textbox1.text+x5;
end;

//6
procedure Form1.button6_Click(sender: Object; e: EventArgs);
begin
  var x6:string;
  x6:='6';
  textbox1.text:=textbox1.text+x6;
end;

//7
procedure Form1.button7_Click(sender: Object; e: EventArgs);
begin
  var x7:string;
  x7:='7';
  textbox1.text:=textbox1.text+x7;
end;

//8
procedure Form1.button8_Click(sender: Object; e: EventArgs);
begin
  var x8:string;
  x8:='8';
  textbox1.text:=textbox1.text+x8;
end;

//9
procedure Form1.button9_Click(sender: Object; e: EventArgs);
begin
  var x9:string;
  x9:='9';
  textbox1.text:=textbox1.text+x9;
end;

//0
procedure Form1.button10_Click(sender: Object; e: EventArgs);
begin
  var x0:string;
  x0:='0';
  textbox1.text:=textbox1.text+x0;
end;

//C
procedure Form1.button11_Click(sender: Object; e: EventArgs);
begin
  textbox1.text:='';
end;

//*
procedure Form1.button12_Click(sender: Object; e: EventArgs);
begin
  firstnum:=textbox1.text;
  action:='*';
  textbox1.text:=textbox1.text+action;
end;

// \
procedure Form1.button13_Click(sender: Object; e: EventArgs);
begin
  firstnum:=textbox1.text;
  action:='/';
  textbox1.text:=textbox1.text+action;
end;

//-
procedure Form1.button14_Click(sender: Object; e: EventArgs);
begin
  firstnum:=textbox1.text;
  action:='-';
  textbox1.text:=textbox1.text+action;
end;

//+
procedure Form1.button15_Click(sender: Object; e: EventArgs);
begin
  firstnum:=textbox1.text;
  action:='+';
  textbox1.text:=textbox1.text+action;
end;

 //=
procedure Form1.button16_Click(sender: Object; e: EventArgs);
begin
var bob:integer;
if action='+' then
  begin
  var sum:real;
  bob:=textbox1.text.lastindexof('+');
  secondnum:=textbox1.text.substring(bob);
  number1:=real.Parse(firstnum);
  number2:=real.Parse(secondnum);
  sum:=number1+number2;
  textbox1.text:=sum.ToString;
  end;

if action='-' then
  begin
  var diff:real;
  bob:=textbox1.text.lastindexof('-');
  secondnum:=textbox1.text.substring(bob);
  number1:=real.Parse(firstnum);
  number2:=real.Parse(secondnum);
  diff:=number1-number2;
  textbox1.text:=diff.ToString;
  end;


end;

procedure Form1.Form1_Load(sender: Object; e: EventArgs);
begin

end;

procedure Form1.textBox1_TextChanged(sender: Object; e: EventArgs);
begin

end;
end.