Why the output is 1?

Question

#include <iostream>
using namespace std;
int s (int a){
return 165;}

int main() {
int(*e)(int)=s;
cout << *e ;

return 0;
}

Answer 1

Because ostream doesn't have an overload for the type 'int(*)(int)'.
It would be impossible to define them all because there are an infinite amount of function pointer types.

The next best option is to convert it to a boolean and since functions can't be located at address 0 they are all evaluated as 1.

You can print the address by overloading int(*)(int) for ostream operator<< yourself.

std::ostream& operator<<( std::ostream& os, int(*p)(int) )
{
return os << (void*)p;
}

What you probably want is
cout << e(5); // 165