I've managed to successfully extract all desired information from the "Optional Header". All those contained within the "Standard" fields and "Windows-specific" fields. However when it came to the "Data Directories" field, I found the values contained within the "Export Table" field were equal to zero.
How can I locate the "Export Table" within the executable.
Adding to DeadMG's answer: the question's title indicates that you're using an EXE file. You will find that most EXEs do not have export tables, since they are not "consumed" by other components. Most often, they act as consumers for other DLLs. EXE files usually import other DLLs, and these DLLs may have non-empty export sections.