CPlusPlus Interview Questions and Answers

Answer - 101 : - A class that has no functionality of its own. Its member functions hide the use of a third party software component or an object with the non-compatible interface or a non-object-oriented implementation.

Answer - 102 : - It is an object of some class whose purpose is to indicate that a real object of that class does not exist. One common use for a null object is a return value from a member function that is supposed to return an object with some specified properties but cannot find such an object.

Answer - 103 : - A class invariant is a condition that defines all valid states for an object. It is a logical condition to ensure the correct working of a class. Class invariants must hold when an object is created, and they must be preserved under all operations of the class. In particular all class invariants are both preconditions and post-conditions for all operations or member functions of the class.

Answer - 104 : - It is a process during exception handling when the destructor is called for all local objects between the place where the exception was thrown and where it is caught.

Answer - 105 : - Precondition: A precondition is a condition that must be true on entry to a member function. A class is used correctly if preconditions are never false. An operation is not responsible for doing anything sensible if its precondition fails to hold. For example, the interface invariants of stack class say nothing about pushing yet another element on a stack that is already full. We say that isful() is a precondition of the push operation. Post-condition: A post-condition is a condition that must be true on exit from a member function if the precondition was valid on entry to that function. A class is implemented correctly if post-conditions are never false. For example, after pushing an element on the stack, we know that isempty() must necessarily hold. This is a post-condition of the push operation.

Answer - 106 : - * The condition should hold at the end of every constructor. * The condition should hold at the end of every mutator (non-const) operation.

Answer - 107 : - Objects that stand for other objects are called proxy objects or surrogates. template class Array2D { public: class Array1D { public: T& operator[] (int index); const T& operator[] (int index)const; }; Array1D operator[] (int index); const Array1D operator[] (int index) const; }; The following then becomes legal: Array2Ddata(10,20); cout< Question - 108 : - What is an orthogonal base class?

Answer - 108 : - If two base classes have no overlapping methods or data they are said to be independent of, or orthogonal to each other. Orthogonal in the sense means that two classes operate in different dimensions and do not interfere with each other in any way. The same derived class may inherit such classes with no difficulty.

Answer - 109 : - A node class is a class that, * relies on the base class for services and implementation, * provides a wider interface to the users than its base class, * relies primarily on virtual functions in its public interface * depends on all its direct and indirect base class * can be understood only in the context of the base class * can be used as base for further derivation * can be used to create objects. A node class is a class that has added new services or functionality beyond the services inherited from its base class.

Answer - 110 : - A container class is a class that is used to hold objects in memory or external storage. A container class acts as a generic holder. A container class has a predefined behavior and a well-known interface. A container class is a supporting class whose purpose is to hide the topology used for maintaining the list of objects in memory. When a container class contains a group of mixed objects, the container is called a heterogeneous container; when the container is holding a group of objects that are all the same, the container is called a homogeneous container.