Other fields are defined in WINNT.H The third component of the PE header is a structure of type IMAGE_OPTIONAL_HEADER. For PE files, this portion certainly isn't optional. The COFF format allows individual implementations to define a structure of additional information beyond the standard IMAGE_FILE_HEADER. The fields in the IMAGE_OPTIONAL_HEADER are what the PE designers felt was critical informa
![Peering Inside the PE: A Tour of the Win32 Portable Executable File Format](https://cdn-ak-scissors.b.st-hatena.com/image/square/d6e4cb632c7025e9f5e05fd314fbf6dcd6144e8d/height=288;version=1;width=512/https%3A%2F%2Flearn.microsoft.com%2Fen-us%2Fmedia%2Fopen-graph-image.png)