explain call by reference with example in c++

Example 1: calling by reference c++

void fun(int *a)
{
   *a = 10;
}

Example 2: calling by reference c++

void fun3(int a)
{
    a = 10;
}

int main()
{
    int b = 1;
    fun3(b);
    // b  is still 1 now!
    return 0;   
}