C++ Interview Questions and Answers

We have listed of C++ Interview Questions and Answers that have been designed for C++ professionals who are preparing interviews on C++ Programming. C++ is not a purely object-oriented language but a hybrid that contains the functionality of the C programming language. The C++ standard library contains predefined and standardized functions that are available for any compiler. Modern compilers normally offer an integrated software development environment, which combines the steps mentioned previously into a single task. A graphical user interface is available for editing, compiling, linking, and running the application.

Best C++ Interview Questions and Answers

Below we have provided best C++ Interview Questions that are specially designed for C++ Programmers.

What is an accessor in C++?

An accessor is a class operation that does not modify the state of an object in C++. The accessor functions need to be declared as const operations.

Differentiate between a template class and class template in C++?

Template class: A generic definition or a parametrized class not instantiated until the client provides the needed information. It’s jargon for plain templates. Class template: A class template specifies how individual classes can be constructed much like the way a class specifies how individual objects can be constructed. It’s jargon for plain classes. 

When does a name clash occur in C++?

A name clash occurs when a name is defined in more than one place. For example, two different class libraries could give two different classes the same name. If you try to use many class libraries at the same time, there is a fair chance that you will be unable to compile or link the program because of name clashes.

Define namespace in C++?

It is a feature in C++ to minimize name collisions in the global name space. This namespace keyword assigns a distinct name to a library that allows other libraries to use the same identifier names without creating any name collisions. Furthermore, the compiler uses the namespace signature for differentiating the definitions.

What is the use of ‘using’ declaration in C++?

A using declaration in C++ makes it possible to use a name from a namespace without the scope operator.

What is an Iterator class in C++?

A class that is used to traverse through the objects maintained by a container class. There are five categories of iterators: input iterators, output iterators, forward iterators, bidirectional iterators, random access. An iterator is an entity that gives access to the contents of a container object without violating encapsulation constraints. Access to the contents is granted on a one-at-a-time basis in order.

The order can be storage order (as in lists and queues) or some arbitrary order (as in array indices) or according to some ordering relation (as in an ordered binary tree). The iterator is a construct, which provides an interface that, when called, yields either the next element in the container, or some value denoting the fact that there are no more elements to examine. Iterators hide the details of access to and update of the elements of a container class. The simplest and safest iterators are those that permit read-only access to the contents of a container class.

What is an incomplete type in C++?

Incomplete types refer to pointers in which there is non availability of the implementation of the referenced location or it points to some location whose value is not available for modification.

int *i=0x400 // i points to address 400

In the above example when PrintVal() function is called it is called by the pointer that has been freed by the destructor in SomeFunc.

What is an adaptor class or Wrapper class in C++?

A class that has no functionality of its own is an Adaptor class in C++. 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.

What is a Null object in C++?

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.

What is class invariant in C++?

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.

What do you mean by Stack unwinding in C++?

Stack unwinding in C++ 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.

Define precondition and post-condition to a member function in C++?

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.

What is the two main roles of Operating System?

As a resource manager As a virtual machine In the derived class, which data member of the base class are visible? In the public and protected sections.

How do you find out if a linked-list has an end?

You can find out by using 2 pointers. One of them goes 2 nodes each time. The second one goes at 1 node each time. If there is a cycle, the one that goes 2 nodes each time will eventually meet the one that goes slower. If that is the case, then you will know the linked-list is a cycle.

What is the difference between realloc() and free()?

The free subroutine frees a block of memory previously allocated by the malloc subroutine. Undefined results occur if the Pointer parameter is not a valid pointer. If the Pointer parameter is a null value, no action will occur. The realloc subroutine changes the size of the block of memory pointed to by the Pointer parameter to the number of bytes specified by the Size parameter and returns a new pointer to the block.

The pointer specified by the Pointer parameter must have been created with the malloc, calloc, or realloc subroutines and not been deallocated with the free or realloc subroutines. Undefined results occur if the Pointer parameter is not a valid pointer.

What are the advantages of inheritance in C++?

It permits code reusability. Reusability saves time in program development. It encourages the reuse of proven and debugged high-quality software, thus reducing problem after a system becomes functional.

What is virtual constructors/destructors?

Virtual destructors:

If an object (with a non-virtual destructor) is destroyed explicitly by applying the delete operator to a base-class pointer to the object, the base-class destructor function (matching the pointer type) is called on the object.

There is a simple solution to this problem declare a virtual base-class destructor.

This makes all derived-class destructors virtual even though they don’t have the same name as the base-class destructor. Now, if the object in the hierarchy is destroyed explicitly by applying the delete operator to a base-class pointer to a derived-class object, the destructor for the appropriate class is called. Virtual constructor: Constructors cannot be virtual. Declaring a constructor as a virtual function is a syntax error.

What is the difference between class and structure in C++?

Structure: Initially (in C) a structure was used to bundle different type of data types together to perform a particular functionality. But C++ extended the structure to contain functions also. The major difference is that all declarations inside a structure are by default public.

Class: Class is a successor of Structure. By default, all the members inside the class are private.

What is RTTI in C++?

Runtime type identification (RTTI) lets you find the dynamic type of an object when you have only a pointer or a reference to the base type. RTTI is the official way in standard C++ to discover the type of an object and to convert the type of a pointer or reference (that is, dynamic typing). The need came from practical experience with C++. RTTI replaces many home grown versions with a solid, consistent approach.

What is encapsulation in C++?

Packaging an object’s variables within its methods is called encapsulation

What is an explicit constructor?

A conversion constructor declared with the explicit keyword. The compiler does not use an explicit constructor to implement an implied conversion of types. It’s purpose is reserved explicitly for construction.

What is the Standard Template Library (STL)?

A library of container templates approved by the ANSI committee for inclusion in the standard C++ specification. A programmer who then launches into a discussion of the generic programming model, iterators, allocators, algorithms, and such, has a higher than average understanding of the new technology that STL brings to C++ programming.

Describe run-time type identification.

The ability to determine at run time the type of an object by using the typed operator or the dynamic cast operator.

What problem does the namespace feature solve?

Multiple providers of libraries might use common global identifiers causing a name collision when an application tries to link with two or more such libraries. The namespace feature surrounds a library’s external declarations with a unique namespace that eliminates the potential for those collisions.

This solution assumes that two library vendors don’t use the same namespace identifier, of course.

Thus, the compilation of these C++ Interview questions includes some of the major points that can be asked during an interview. The C++ interviewers generally check the base knowledge of a candidate, which can be gained by practicing these questions prior interview.

So if you have finally found your dream job in C++ but are wondering how to crack the C++ Interview and what could be the probable C++ Interview Questions. Every interview is different and the scope of a job is different too. Hope above assist you to get a dream Job. Keep Learn.