词法分析的主要任务是：从左到右逐个字符地扫描源程序，产生一个个单词(Token)，同时检查源程序中的词法错误。执行词法分析的程序称为词法分析程序或扫描程序(Scanner)。-The main task of lexical analysis: one by one character to scan from left to right source to generate a one word (Token), also check the source of lexical errors.