What is the output of this program ?

       #include
        using namespace std;
        int n(char, int);
        int (*p) (char, int) = n;
        int main()
        {
            (*p)('d', 9);
            p(10, 9);
            return 0;
        }
        int n(char c, int i)
        {
            cout << c <<  i;
            return 0;
        }

The function declaration should be preceded by the keyword friend.The function definitions does not use either the keyword or the scope operator :: The functions that are declared with the keyword friend as friend function.Thus, a friend function is an ordinary function or a member of another class.

Dynamic binding (also known as late binding) means that the code associated with a given procedure call is not known until the time of the call at run time.It is associated with polymorphism and inheritance.

A default constructor is a constructor that either has no parameters, or if it has parameters, all the parameters have default values.

Copy constructor is a constructor function with the same name as the class and used to make deep copy of objects.

ConstKeyword indicates that memory once initialized, should not be altered by a program.
Volatile keyword indicates that the value in the memory location can be altered even though nothing in the program.
Mutable keyword indicates that particular member of a structure or class can be altered even if a particular structure variable, class, or class member function is constant.

A reference variable provides an alias to a previously defined variable.
Data -type & reference-name = variable name

A destructor is automatically called when the object is destroyed. A virtual destructor in C++ is used primarily to prevent resource leaks by performing a clean-up of the object.

C requires all the variables to be declared at the beginning of a scope but in c++ we can declare variables anywhere in the scope. This makes the programmer easier to understand because the variables are declared in the context of their use.