完成词法分析任务的程序称为词法分析程序或词法分析器或扫描器。从左至右地对源程序进行扫描，按照语言的词法规则识别各类单词，并产生相应单词的属性字。-Completion of lexical analysis task of the program called lexical analysis program or lexical analyzer or scanner. From left to right for source program to scan, according to the language of the lexical rules to identify all kinds of words, and generate the corresponding word attribute word.