C function declaration within another function

Question

can anyone explain these lines to me:

int xyz( void )  
{ 
extern void abc( void );
}

a function declaration within a function definition?

Answer 1

I would just add that this construct, in my experience, is uncommon in modern code, but often seen in older code, especially "K&R" C code.

More modern code would usually get the function prototype from a header file.