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...
  TMeinEdit = class(TEdit)
  private
    FAlignment: TAlignment;
  published
    property Alignment: TAlignment read FAlignment write SetAlignment;

procedure TMeinEdit.SetAlignment (Value: TAlignment);
begin
  FAlignment := Value;
  RecreateWnd;
end;					

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type
  TForm1 = class(TForm)
    Erg: TEdit;

    Panel1: TPanel; Panel2: TPanel;

    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 FormCreate(Sender: TObject);
    procedure ZahlenClick(Sender: TObject);
    procedure ZeichenClick(Sender: TObject);
    procedure ErgebnisClick(Sender: TObject);
    procedure ClearEditClick(Sender: TObject);
    procedure ClearAllClick(Sender: TObject);
    procedure PlusMinusClick(Sender: TObject);
    procedure PunktClick(Sender: TObject);
    procedure ErgClick(Sender: TObject);
    procedure ErgKeyPress(Sender: TObject; var Key: Char);
    procedure FormKeyPress(Sender: TObject; var Key: Char);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  Form1: TForm1;
  Zahl1, Zahl2, Ergebnis: Real;
  Zeichen: Integer;
  Loeschen, Merker, Enter: Boolean;

const

DEFAULT = 0;

implementation

{$R *.dfm}					

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procedure Register;
begin
  RegisterComponents('Eigene', [TMeinEdit]);
end;					

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procedure TMeinIntEdit.KeyPress(var Key: Char);
begin
  inherited KeyPress(Key);
  if not (Key in ['0'..'9']) then
    key := #0;
end;					

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TMeinIntEdit = class (TMeinEdit)
  protected
    procedure KeyPress(var Key: Char); override;
end;