这里以开始定义的PASCAL语言子集的源程序作为词法分析程序的输入数据。

在词法分析中，自文件头开始扫描源程序字符，一旦发现符合"单词"定义的源程

序字符串时，将它翻译成固定长度的单词内部表示，并查填适当的信息表。经过

词法分析后，源程序字符串（源程序的外部表示）被翻译成具有等长信息的单词

串（源程序的内部表示），并产生两个表格：常数表和标识符表，它们分别包含

了源程序中的所有常数和所有标识符。-Here to begin the definition of a subset of the PASCAL language source program as a lexical analysis of input data. In lexical analysis, since the beginning of the first scan source document characters, once in line with the " word"　when the definition of the source string to translate it into fixed-length internal word said, and check the appropriate information sheet to fill. After lexical analysis, the source string (the external source said) has been translated into words, such as long strings of information (the internal source said), and two forms: constant table and the identifier table, which contain, respectively, the source of all the constants and all identifiers.