A new method to form ROM devices in the manufacture of an integrated circuit device is achieved. With this device it is possible to arrange a drive for automatic adjustment of the tension of the strings of the string instrument in a space-saving manner and in the smallest possible amount of space. The display unit displays an object of a folder with a hierarchical structure. The grooves define surfaces effective to redirect light that passes through said window. The priority assigned to the transit packet is determined and when it has a low priority then the transit packet is removed and a higher priority packet is inserted in the resulting vacancy.