然后，它存储一个对PDOM中的单元文件的引用以及对所包含的指令和宏定义的其他引用。

Then, it stores a reference to the unit's file in the PDOM, along with references to the included directives and macro definitions.

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使用指令可以有条件地处理生成文件，显示错误消息，包括其他生成文件，取消定义宏以及打开或关闭某些选项。

Using directives, you can conditionally process your makefile, display error messages, include other makefiles, undefine a macro, and turn certain options on or off.

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