简单词法分析器构造在开始状态，首先要读进一个字符。若读入的是一个空格（包括blank,tab,newline）就跳过它，再继续读字符，直到读进一个非空字符为止。

在标识符状态，识别并组合出一个标识符之后，还必须加入一些动作，以便查保留字表，确定识别出的单词符号是保留字，还是用户自定义标识符，并输出相应的记号。

在无符号数状态，可识别出各种常数，包括整数在内。在组数的同时，还要做从十进制数到二进制数的转换。

-A simple lexical analyzer constructed at the beginning of the state, first of all to read into a character. If the read is a space (including the blank, tab, newline) will skip it, and then continue to read characters until the time into a non-empty character so far. In the identifier state, to identify and assemble an identifier, you must also add some actions in order to check a reserved word table to determine the identify of the word symbols are reserved words, or user-defined identifier, and output the corresponding symbol. In the unsigned status, can identify a variety of constants, including the integer included. In the group number, we must also do a number from decimal to binary number conversion.