该程序的功能是从缓冲区中读取键入字符并显示在屏幕上，当按下left_shift键（扫描码为42d)的同时，又按下0-9或a-z等键，则显示键的上档符号或大写字母。按动除left_shift键以外的控制键或功能键时，则退出。 -The program s function is to read from the buffer and type the characters displayed on the screen, when the press left_shift key (scan code for 42d) while pressing the keys 0-9 or az, etc., it shows the key file symbols or capital letters. In addition to keys pressed left_shift outside the control keys or function keys, then exit.