.def files C/C++ DLLs

Question

I am not understanding the point of using .def files with DLLs.

It seems that it replaces the need to use explicit exports within your DLL code (ie. explicit __decls

Answer 1

.DEF files were more common in 16-bit windows where they were usually the only way to specify which symbols should be exported.

In addition, they provided a means to specify exports by ordinal value (@1, @2 etc.) rather than by name. This method of looking up symbols was used when performance was really important, such as in video drivers.