A hydraulic system has a valve assembly with two workports coupled to chambers of first and second cylinders which are connected mechanically in parallel to a machine component. In particular, the present invention is directed to a book holder with easy loading and unloading of reading material, a page turning mechanism, book centering mechanism andor a foldable book holder stand. The ferrule of this system includes an alignment protrusion and a complementary alignment hole on the front face of the ferrule for providing the fine alignment. Even when the power is shut off in the process of updating the page, at the next start time, the status of the data writing operation when the power is shut off is determined based on the validity and stability of the pages. The system comprises user interface configured for selecting a first symbol having a first display priority; and means for assigning a second display priority to a second symbol associated with the first symbol, wherein the second symbol is displayed according to the second display priority, in response to a request for displaying a symbol set. The treatment method provided by the invention results in a chemically inert waste, a limitation on the volume of wastes obtained, while allowing the removal or even recovery of these wastes by appropriate processing streams.