C++ Quiz Programs Part - 1

Q : is the following program valid? Yes/No give the reason.

 #include <iostream>  
 using namespace std;  
 int main()  
 {  
      int ____123 =123;  
      cout <<"Hello World! "<<____123<<"\n";  
      return 0;  
 }  

A : Yes the above program is valid. in C & C++ identifier name can/should start with _ or [a-zA-Z]. It cant contain any space or special characters in it.

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Q : Write a program to add two numbers without using assignment operator.

A : Remember when we were kids we used to add numbers one by one counting the fingers. Example 5 + 4 = 5 + 1 = 6 + 1 = 7 + 1 = 8 + 1 = 9 . Simple problem solved :) Add one by one in a loop using ++ operator.

 #include<iostream>  
 using namespace std;  
 int main()  
 {  
      int a,b;  
      cout<<"Enter Two Numbers :";  
      cin >>a>>b;  
      while(b--)++a;  
      cout<<"Result :"<<a<<endl;  
 }  

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Q : in C++ can a have Anonymous class?

A : In C++ classes can be anonymous ie., they can be declared without an identifier.

 #include<iostream>  
 using std::cout;  
 class{  
      private:  
           int a;  
      public:  
           void init()  
           {  
                a=10;  
           }  
           void display()  
           {  
                cout<<"i m display() - member function "<<a<<"\n";  
           }  
 }A,B;  
 int main()  
 {  
      A.init();  
      A.display();  
      B.display();  
 }  

Output:
i m display() - member function 10
i m display() - member function 0

Here A and B are the instance of the anonymous class. Member functions of anonymous classes can be called like normal class member functions.

Anonymous classes comes with some restrictions.

They can't have constructor or destructor [ofcourse they don't have a name].

They can't be passed as a function argument. Even if we pass them as an argument to a function with Ellipses, it will abort at runtime. But the compiler wont complain any error as Ellipses skips type checking.

They cannot be returned as return values from functions.

No class can inherit from anonymous class, Remember they don't have name

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Q : Inheritance and Anonymous class is it valid?

A : Yes. Check the below program

 #include<iostream>  
 #include <stdarg.h>  
 using std::cout;  
 class Base  
 {  
    public:  
        int a;  
        Base():a(7){}  
        void parentDisplay(){  
               cout<<"Parent Class value of a :"<<a<<"\n";  
          }  
 };  
 class : public Base  
 {  
    public:  
       void childDisplay()  
       {  
          cout<<"Child Class - ";  
          parentDisplay();  
       }  
 } AnonymousInherited;  
 int main()  
 {  
      AnonymousInherited.parentDisplay();  
      AnonymousInherited.childDisplay();  
 }  

Output:
Parent Class value of a :7
Child Class - Parent Class value of a :7

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Q : Tell something about anonymous union?

A : Union can be anonymous. But we should know the restrictions of anonymous unions. They are

They can't have constructor and destructor.

Anonymous unions can't have member functions.

Anonymous unions can't be inherited from any other union.

Example:

 #include<iostream>  
 using std::cout;  
 int main()  
 {  
   union Base  
   {  
     int x;  
   };  
      union : Base // Error here  
      {  
           int a;  
           char c;  
           void display(){cout<<" a : "<<a<<"\n";} // Error here  
      };  
      a = 97;  
      cout<<" c : "<<c<<"\n";  
 }  

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