实现一个词法分析器，词法分析程序的主要任务是从左到右扫描每行源程序，拼成单词，换成统一的内部表示 (token)输出，送给语法分析器。具体包括：

–组织源程序的输入；

–按规则拼单词，并转换成二元形式；

–滤掉空白符，跳过注释、换行符及一些无用的符号(如字符常数的引号) （实验一已完成）；

–进行行列计数，用于指出出错的行列号，并复制出错部分；

–列表打印源程序；

–发现并定位词法错误；

–生成符号表。token 文件和符号表用作语法分析的输入部分。

-Implement a lexical analyzer, lexical analysis program' s main task is scanned from left to right each line source, makes up words, and replaced with a unified internal representation (token) output, given parser. These include:- Organization of the input source - word fight by the rules, and converted into binary form - filter out the blank character, skip notes, line breaks and some useless symbols (such as character constants quotation marks) (experimental 1 has been completed) - to the ranks of count, the ranks for that error number, and copy the wrong part of it - list of print source - find and locate lexical errors - generate symbol table. token file and symbol table as part of parsing the input.