词法分析程序的功能是，接受一个表达式，输出该表达式中的各类单词符号。测试词法分析程序时，可以按照一定格式输出各类单词符号。

本程序实现整数四则运算表达式的词法分析程序。-Lexical analyzer function is to accept an expression, the output of the expression of the various types of word symbols. Testing lexical analysis program, you can format the output according to certain types of word symbols. This procedure to achieve an integer 4 expression is the lexical analysis program.