Interview Questions

C++ Back

What are the conditions that have to be met for a condition to be an invariant of the class?

Ans:  The condition should hold at the end of every constructor, The condition should hold at the end of every mutator(non-const) operation.

Define precondition and post-condition to a member function?

Ans:  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.

What do you mean by Stack unwinding?

Ans:  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.

What is class invariant?

Ans:  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 is a Null object?

Ans:  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 an adaptor class or Wrapper class?

Ans:  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.

Differentiate between the message and method.

Ans:  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.

What is a dangling pointer?

Ans:  A dangling pointer arises when you use the address of an object after its lifetime is over.This may occur in situations like returning addresses of the automatic variables from a function or using the address of the memory block after it is freed.

What is an incomplete type?

Ans:  Incomplete types refers 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. Example: int *i=0x400 // i points to address 400 *i=0; //set the value of memory location pointed by i. Incomplete types are otherwise called uninitialized pointers.

List out some of the object-oriented methodologies.

Ans:  Object Oriented Development (OOD) (Booch 1991,1994), Object Oriented Analysis and Design (OOA/D) (Coad and Yourdon 1991),Object Modelling Techniques (OMT) (Rumbaugh 1991), Object Oriented Software Engineering (Objectory) (Jacobson 1992),Object Oriented Analysis (OOA) (Shlaer and Mellor 1992), The Fusion Method (Coleman 1991)..