Object-Oriented Programming

Virtual functions enable runtime polymorphism through dynamic binding. When a virtual function is overridden in derived classes, the correct function version is called based on the actual object type, not the pointer type. This allows different behaviors for the same function call across different classes in an inheritance hierarchy.

Static member variables are initialized to 0 when the first object of the class is created, and this initialization happens only once. They are shared among all objects of the class and retain their values between object creations. They are not re-initialized to 1 each time, and they are not visible outside the class unless declared public.

Friend functions are declared inside a class but defined outside. They're not affected by public/private/protected sections - placement makes no difference to meaning. They're not member functions, so they need object references to access members, and can be called independently.

A default constructor takes no parameters. Option B has star() with no parameters, making it the default constructor. Options A and C have constructors with parameters (parameterized constructors), not default constructors.

Non-leaf classes are abstract and can have further subclasses.

Virtual functions in base classes enable runtime polymorphism through dynamic binding. Even if not directly used in the base class, they must be declared to establish the interface for derived classes to override.

Multilevel inheritance occurs when a derived class itself becomes a base class for another class, forming a chain. Hierarchical inheritance has multiple derived classes from one base. Multiple inheritance means deriving from multiple base classes.

Object pointers cannot directly access private members. Access specifiers apply regardless of whether you use an object or a pointer to an object. Private members are only accessible within member functions or friends.

C++ has exactly four storage classes: auto (default for local variables), register (suggests CPU register storage), static (preserves value between function calls), and extern (for global/external linkage).

In C++, structures (struct) have public access by default, unlike classes where members are private by default. This is a fundamental distinction between struct and class. Protected is used for inheritance scenarios, and 'none of these' is incorrect since public is the default.

This is the correct answer, as there are 4 constructors of HashTable Class in java collections framework. These constructors are Hashtable, Hashtable(int initialCapacity, Hashtable(int initialCapacity, float loadFactor)Hashtable(Map t).

This is the correct answer. There are four constructors of TreeMap. These are :-TreeMap():- create an empty Map, TreeMap(Comparator comp):- The second form constructs an empty tree-based map that is sorted by using the Comparator comp, TreeMap(Map m):- The third form initialises a tree map with the entries from m, which is sorted by using the natural order of the keys, and TreeMap(SortedMap sm):- The fourth form initialises a tree map with the entries from sm, which is sorted in the same order as sm.

This is correct, as there are 4 constructors of HashMap class. These are :-HashMap() :- Constructs an empty HashMap with the default initial capacity (16) and the default load factor (0.75). HashMap(int initialCapacity) :- Constructs an empty HashMap with the specified initial capacity and the default load factor (0.75). HashMap(int initialCapacity, float loadFactor) :- Constructs an empty HashMap with the specified initial capacity and load factor. HashMap(Map<? extends K,? extends V> m) :- Constructs a new HashMap with the same mappings as the specified Map.

The final keyword in Java prevents a class from being inherited (subclassed). When applied to a class, it makes the class non-inheritable, which is useful for security or design purposes when you want to prevent extension.