对PL/0作以下修改扩充：

（1）课内上机作业（考试前交报告）：

增加单词：保留字 ELSE，FOR，TO, DOWNTO

运算符 +=，-=，++，--

修改单词：不等号# 改为 <>

增加条件语句的ELSE子句

-right PL / 0 expansion for the following modifications : (1) the reverse on the plane operations (examination reports) : Increased words : reserved words ELSE, FOR, TO, DOWNTO Operators =,-=,, -- changes the words : re # sign of inequality