What are C macros useful for?

Question

I have written a little bit of C, and I can read it well enough to get a general idea of what it is doing, but every time I have encountered a macro it has thrown me complet

Answer 1

By leveraging C preprocessor's text manipulation one can construct the C equivalent of a polymorphic data structure. Using this technique we can construct a reliable toolbox of primitive data structures that can be used in any C program, since they take advantage of C syntax and not the specifics of any particular implementation.

Detailed explanation on how to use macros for managing data structure is given here - http://multi-core-dump.blogspot.com/2010/11/interesting-use-of-c-macros-polymorphic.html