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说明：  程序先把显示模式设置每行80个字符，并将屏幕设置成白色，然后清屏，画一个窗口，并将其前景设为白色，背景色设为红色，在窗口中输出能够显示的最大行数，按任意键后，把显示模式改为每行80个字符，刷新屏幕，再改为每行40个字符的显示模式
(Procedures first display mode settings 80 characters per line, and the screen set to white, and then clearance screen, painting a window, and its prospects as white, the background color set to red, in the output window can display the maximum line number, press any key after the display mode is changed to 80 characters per line, to refresh the screen, and then changed to 40 characters per line display mode)