For example import table
Its virtual address and size is written both data directory and Section table (.idata)
The same information both in d.d and s.t.
So why is is there data directory?Why do we use it?

What are the differences between Data Directory and Section Table

The section table defines the size of the section, while the entries in the data directory define the size of the data block that contains the specified information e.g. imports.

In a single-section PE (can easily be created by assemblers, but compilers also have the capability - it reduces the filesize nicely too ) the only entry in the section table would define the size of the entire section, while the entry for imports in the data directory would define the size of the portion that contained import data.

If I remember correctly, Windows ignores the size of imports specified in the data directory and only uses the location pointer.

thanks llxx