var Form1: TForm1;a,b,c:real;implementation{$R *.dfm}procedure TForm1.Edit2Change(Sender: TObject);begina:=StrToIntDef(DBEdit1.Text,0);b:=StrToIntDef(Edit2.Text,0);c:=a*b;Edit3.Text:=FloatToStr(c);if Edit2.Text='' thenShowMessage('data harus di isi');Form1.Refres...