The difference analysis between C and C + + parameter-free function

In the "C + + programming Idea": "About the parameterless function declaration, C and C + + are very different." In C, declaring an int fun1 () means a function that can have any number and type, whereas in C + + it is a function with no parameters.

Here is a C-language function and C + + function to validate this passage

Copy Code code as follows:
# include<stdio.h>

int fun1 ();

int main ()
{
int a = FUN1 (3, 4);
printf ("%dn", a);
return 0;
}

int fun1 (int a, int b)
{
return a + B;
}

The result is no problem, the output is 7, or fun () can declare fun (int, int)

Copy Code code as follows:
# include<iostream>
using namespace Std;

int fun1 ();

int main ()
{
int a = FUN1 (3, 4);
cout << a << Endl;

return 0;
}

int fun1 (int a, int b)
{
return a + B;
}

Compilation error, "FUN1": function does not accept 2 parameters. Description in C + + fun () can not declare fun (int, int)