掌握使用I/O流进行数据读写的方法。假设有一家商店，需要一个存货目录

来记录每种工具的名称、数量、价格。工具的初始信息存放在hardware.dat 文件中。GUI界面包括一个面板和两个按钮。按下“显示”按钮，面板以表格形式显示工具信息。可以在卖货或进货（该商店可能买入新品种工具）后，在GUI界面上对工具信息进行更新，按下“提交”按钮，更新后的信息保存到文件中。

-Master the use of I/O reads and writes data stream approach. Suppose a store, you need an inventory directory to keep track of each tool' s name, quantity, price. Tool hardware.dat initial information stored in the file. GUI interface includes a panel and two buttons. Press the " Show"　button, panel display tool information in tabular form. You can sellers or purchase (which stores may sell new varieties of tools) after GUI interface to update the information on tools, press the " submit"　button, the updated information is saved to a file.