What is forward reference in C?

Question

What is forward reference in C with respect to pointers?

Can I get an example?

Answer 1

Adding to previous answers. The typical situation in which forward reference is mandatory is when a struct foo contains a pointer to a struct bar, and bar contains a pointer to foo (a circular dependency between declarations). The only way to express this situation in C is to use a forward declaration, i.e.:

struct foo;

struct bar
{
   struct foo *f;
};

struct foo
{
   struct bar *b;
};