说明：  扩展PL/0编译程序功能，通过阅读、研究PL/0编译程序源文件，有选择地补充、完善其中词法分析、语法分析、语义分析、目标代码生成、目标代码解释执行等部分的功能。以语法分析部分为例，则可以增加处理更多语法成分的功能，可处理++、--、+=、-=、*=、/=、%（取余）、！（取反）、for、else、处理注释、错误提示
(Extending the function of PL/0 compiler, by reading and studying the source files of PL/0 compiler, we selectively complement and improve the functions of lexical analysis, syntax analysis, semantic analysis, target code generation, target code interpretation and execution. Taking the grammar analysis part as an example, it can increase the function of processing more grammatical components, and can handle + +, -, + +, - =, * =, / =,% (extra),! (reverse), for, else, processing notes, error prompts)