cmm语法分析器从输入的源程序中，识别出各个具有独立意义的记号，包括保留字、标识符、常数、运算符、分隔符等，并依次输出各个记号序列。-cmm parser an input source, the identification of the various independent significance of the mark, including the reserved words, identifiers, constants, operators, separators, etc.,