procedure TForm1.Button1Click(Sender: TObject);
var
hEdit: HWND;
str: string;
begin
str := '准备要添加到记事本的字符串';
WinExec('Notepad.exe', SW_SHOWNORMAL);
hEdit := GetWindow(GetForegroundWindow, GW_CHILD);
SendTextMessage(hEdit, WM_SETTEXT, 0, str);
end;