u3.pas

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unit U3;

interface

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

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    ComboBox1: TComboBox;
    Button1: TButton;
    Button2: TButton;
    StaticText1: TStaticText;
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure ComboBox1Change(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button2Click(Sender: TObject);
begin
  close;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if Trim(statictext1.Caption)='+' then
    Edit3.Text:=FloatToStr(StrToFloat(Edit1.Text)+
            StrToFloat(Edit2.Text));
  if Trim(statictext1.Caption)='-' then
    Edit3.Text:=FloatToStr(StrToFloat(Edit1.Text)-
            StrToFloat(Edit2.Text));
  if Trim(statictext1.Caption)='*' then
    Edit3.Text:=FloatToStr(StrToFloat(Edit1.Text)*
            StrToFloat(Edit2.Text));
  if Trim(statictext1.Caption)='/' then
    Edit3.Text:=FloatToStr(StrToFloat(Edit1.Text)/
            StrToFloat(Edit2.Text));
end;

procedure TForm1.ComboBox1Change(Sender: TObject);
begin
  statictext1.caption:=combobox1.text;
end;

end.