Technical interview questions and answers play a major role in C++ Interviews because C++ is widely used in system programming, game development, competitive coding, and performance-critical applications. Companies expect candidates to know OOP concepts, classes, inheritance, polymorphism, references, memory management, STL, and exception handling. These questions often appear in campus placements and software interviews conducted by TCS, Wipro, Infosys, Cognizant, and Capgemini. This guide covers frequently asked C++ interview questions with simple explanations that help freshers and job seekers strengthen their programming foundation. Preparing these questions will help you perform well in coding tests, technical rounds, and real-time problem-solving interviews.
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11. Differentiate between the message and method.
Message
Objects communicate by sending messages to each other.
A message is sent to invoke a method.
Method
Provides response to a message.
It is an implementation of an operation.
12. What is an adaptor class or Wrapper class?
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 nonobject-
oriented implementation.
13. What is a Null object?
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.
14. What is class invariant?
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.
15. What do you mean by Stack unwinding?
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.
16. Define precondition to a member function.
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.
17. Define post-condition to a member function.
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.
18. What are the conditions that have to be met for a condition to be an invariant of the
class?
Ø The condition should hold at the end of every constructor.
Ø The condition should hold at the end of every mutator(non-const) operation.
19. What are proxy objects?
Objects that stand for other objects are called proxy objects or surrogates.