ABAP里面的OCCURS与HEADER LINE之间的一些区别

This addition to the statements DATA TABLE OF, DATA RANGE OF, and the obsolete statement DATA OCCURS (which is not allowed in classes) declares a further data object alongside the internal table, known as the header line. This object has exactly the same name as the internal table and has the row type of the internal table as its data type. A header line cannot be declared for internal tables with a table-like row type. This is possible for structured row types with table-like components, however. 

我用中文总结一下：

OCCURS与HEADER LINE都是用来定义内表的语句，OCCURS是3.0版本之前的语句，在4.0系统中已经过时，不推荐使用。但是前者在定义一个内表的同时，还定义了一个数据对象（这个东西其实就是一个工作区，与内表的结构是完全一样的，之后也就演变成了所谓的header line）。