Identifier list Vs Parameter type list in C

Question

6.7.6.3 Function declarators (including prototypes)

This part of the standard deals with \'Identifier list\' and \'Parameter typ

Answer 1

In C11 standard

6.7.6.3 Function declarators (including prototypes)
Constraints

D( parameter-type-list )
or
D( identifier-listopt )  

While declaring function you need not give identifiers list. BUt you should at least mention type list

example:

int sum(int,int); //declaration  

int sum(int a,int b); //declaration

both are declaration of same function .

but second one you also mentioned identifiers that is optional.