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var
  Form1: TForm1;
  Zahl1: integer;
  Zeichen: char;

implementation

{ TForm1 }

procedure TForm1.AdditionsBTClick(Sender: TObject);
begin
     Zahl1:=strtoint (EingabeED.text);
     EingabeED.text:='';
end;

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

procedure TForm1.RechneBTClick(Sender: TObject);
begin
  EingabeED.text:=inttostr(Zahl1+strtoint(EingabeED.text));
end;

initialization
  {$I unit1.lrs}

end.                    

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program project1;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes, SysUtils, CustApp
  { you can add units after this }, Unit1;

type

  { TMyApplication }

  TMyApplication = class(TCustomApplication)
  protected
    procedure DoRun; override;
  public
  end;

{ TMyApplication }

procedure TMyApplication.DoRun;
var
  ErrorMsg: String;
begin

  { add your program here }

  // stop program loop
  Terminate;
end;

var
  Application: TMyApplication;
begin
  Application:=TMyApplication.Create(nil);
  Application.Title:='rechner';
  Application.CreateForm(TForm1, Form1);
  Application.Run;
  Application.Free;
end.