#programming closed

Question

It is mandatory , the function should have prototype function in main because if the function is not declared at the point of the call, the compiler "guesses" (infers) the declaration implicitly from the types of the arguments passed in the call and assumes that the return type is int. 

My question is it gives syntactically error or compilation error or no error if we are not defining prototype function in main.

Answer 1

This guess was there only before C11 standard. Now, as per C11, it is a MUST that we should give prototype. Else, compiler may throw warning or error- it is up to compiler implementation.