说明：  词法分析器：源程序的运行方式： 运行程序 输入一个已存在的文本文档的文件名。如：input.txt 如果要对整个程序进行语法分析，则按‘y’键，否则按‘n’键 如果要对程序进行语法分析，则按‘y’键，否则按‘n’键 程序结束
(lexical analyzer : the source of the mode of operation : the importation of operational procedures already exist in a text file in the file name. Such as : input.txt if the entire procedure syntax analysis, the provision 'y' button, or by the 'n' key to the procedure syntax analysis, the provision 'y' button, or by the 'n' key end of the program)