词法分析器,包括的关键字表和符号表,是针对C语言的，由于关键字表和符号表是在文本文档里建的，所以可以扩展,程序的可移植性比较好-lexical analyzer, including keyword table and symbol table is targeted at the C language, and keyword table is the symbol table in the text files in the building, so it can be extended, procedures portability better