说明：  程序描述：这个范例说明如何使用８０５１的Ｐ１口连接到４个七段显示器，Ｐ０口的低四位分别显示这四个共阳七段显示器，让４个七段显示器使用扫描的方式轮流显示数字．
(Description: This example illustrates how to use the 8051 port to connect to the P1 paragraph 4 displays, P0 4, respectively, with low population showed a total of four seventh-yang display, so that paragraph 4 of the way of scanning the display alternately shows the number of .)