一．　　PL/0语言建立一个词法分程序GETSYM（函数）

把关键字、算符、界符称为语言固有的单词，标识符、常量称为用户自定义的单词。为此设置三个全程量：SYM,ID,NUM 。

SYM：存放每个单词的类别，为内部编码的表示形式。

ID：存放用户所定义的标识符的值，即标识符字符串的机内表示。

NUM：存放用户定义的数。

-A. PL/0 language known as keywords, operators, delimiters language inherent in the word, the establishment of a lexical the program GETSYM (function) identifiers, constants, called user-defined words. This setting three full amount: SYM, ID, NUM. SYM: storing the category of each word, for the representation of the internal coding. ID: storing user-defined identifier value identifier string inside. NUM: storing user-defined number.