说明：  PL／0语言的文法规则 说明 (1)对原PL／0编译程序作了如下修改： 1’增加了输入文件ff和fi,输出文件fw2。 2’增加了保留字read和write，使保留字个数增至13。 3’关系运算符中的>=、<=和<>改为在过程getsym中说明。 4’在过程interpret中增加了读和写操作。 (2)预先建立PL／0语言源程序文件ff和其所需要的数据文件fi(文件名预先确定)。 (3)运行时在键盘上根据提示信息键入输出文件fw2的文件名(自行随时确定)。
(PL/0 language grammar rules (1) the original PL/0 compiler was amended as follows : 1 'increase in the importation and fi ff paper, the output document fw2. 2 'a reserved word read and write, make reservations number to 13 characters. 3 'relations Operators of gt; =, Lt; = And lt; Gt; Getsym changed in the process described. 4 'in the process interpret added to the read and write operations. (2) pre-establish PL/0 ff language source files and the data they need fi document (document were pre-determined). (3) running at the keyboard on the basis of a message typing output files fw2 document (identify themselves at any time).)