C++ OOP Interview/TopOfMind Questions

What will be printed as the result of the operation below: main() { char s1[]="Cisco"; char s2[]= "systems"; printf("%s",s1); }

Cisco

What will be printed as the result of the operation below: main() { char *ptr = " Cisco Systems"; *ptr++; printf("%sn",ptr); ptr++; printf("%sn",ptr); }

Cisco Systems

What will be printed as the result of the operation below: main() { char *p1; char *p2; p1=(char *)malloc(25); p2=(char *)malloc(25); strcpy(p1,"Cisco"); strcpy(p2,"systems"); strcat(p1,p2); printf("%s",p1); }

Ciscosystems

What is the difference between a copy constructor and an overloaded assignment operator?

A copy constructor constructs a new object by using the content of the argument object. An overloaded assignment operator assigns the contents of an existing object to another existing object of the same class

What is the difference between an external iterator and an internal iterator? Describe an advantage of an external iterator.

.An internal iterator is implemented with member functions of the class that has items to step through. .An external iterator is implemented as a separate class that can be "attach" to the object that has items to step through. .An external iterator has the advantage that many difference iterators can be active simultaneously on the same object.

Write a program that ask for user input from 5 to 9 then calculate the average( Asked by Cisco system people)

.int main() { int MAX=4; int total =0; int average=0; int numb; cout<<"Please enter your input from 5 to 9"; cin>>numb; if((numb <5)&&(numb>9)) cout<<"please re type your input"; else for(i=0;i<=MAX; i++) { total = total + numb; average= total /MAX; } cout<<"The average number is"<<average<<endl; return 0; }

What is meant by Dynamic binding?

Dynamic binding is a binding in which the class association is not made until the object is created at execution time. It is also called as Late binding.

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.

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 non-object-oriented implementation.

What is an Iterator class?

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 a conversion constructor?

A constructor that accepts one argument of a different type.

What is a container class? What are the types of container classes?

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.

What is a dangling pointer?

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. The following code snippet shows this: class Sample { public: int *ptr; Sample(int i) { ptr = new int(i); } www.freshersparadise.com ~Sample() { delete ptr; } void PrintVal() { cout << The value is << *ptr; } }; void SomeFunc(Sample x) { cout << Say i am in someFunc << endl; } int main() { Sample s1 = 10; SomeFunc(s1); s1.PrintVal(); } 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 a modifier?

A modifier, also called a modifying function is a member function that changes the value of at least one data member. In other words, an operation that modifies the state of an object. Modifiers are also known as mutators . Example: The function mod is a modifier in the following code snippet: class test { int x,y; public: test() { x=0; y=0; } void mod() { x=10; y=15; } };

When does a name clash occur?

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.

What is a node class?

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.

What is Overriding

A process of creating different implementation of a method having a same name as base class, in a derived class. It implements Inheritance.

What is the use of using declaration.

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

What will be printed as the result of the operation below: main() { int x=20,y=35; x=y++ + x++; y= ++y + ++x; printf("%d%dn",x,y); }

Answer : 5794

What will be printed as the result of the operation below: #define swap(a,b) a=a+b;b=a-b;a=a-b; void main() { int x=5, y=10; swap (x,y); printf("%d %dn",x,y); swap2(x,y); printf("%d %dn",x,y); } int swap2(int a, int b) { int temp; temp=a; b=a; a=temp; return 0; }

Answer: 10, 5

What will be printed as the result of the operation below: main() { int x=10, y=15; x = x++; y = ++y; printf("%d %dn",x,y); }

Answer: 11, 16

What is a Class?

Class is a template for a set of objects that share a common structure and a common behavior.

What is an Abstract Class?

Abstract class is a class that has no instances. An abstract class is written with the expectation that its concrete subclasses will add to its structure and behavior, typically by implementing its abstract operations.

What is meant by abstraction?

Abstraction defines the essential characteristics of an object that distinguish it from all other kinds of objects. Abstraction provides crisply-defined conceptual boundaries relative to the perspective of the viewer. Its the process of focusing on the essential characteristics of an object. Abstraction is one of the fundamental elements of the object model.

What are the core OOP's concepts?

Abstraction, Encapsulation, Inheritance and Polymorphism are the core OOP's concepts.

What is Overloading?

Adding a new method with the same name in same/derived class but with different number/types of parameters. It implements Polymorphism.

What is an accessor?

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

What is an Instance?

An instance has state, behavior and identity. The structure and behavior of similar classes are defined in their common class. An instance is also called as an object.

What will be printed as the result of the operation below: int x; int modifyvalue() { return(x+=10); } int changevalue(int x) { return(x+=1); } void main() { int x=10; x++; changevalue(x); x++; modifyvalue(); printf("First output:%dn",x); x++; changevalue(x); printf("Second output:%dn",x); modifyvalue(); printf("Third output:%dn",x); }

Answer: 12 , 13 , 13

What will be printed as the result of the operation below: main() { int x=5; printf("%d,%d,%dn",x,x< <2,x>>2); }

Answer: 5,20,1

What will be printed as the result of the operation below: main() { int a=0; if(a==0) printf("Cisco Systemsn"); printf("Cisco Systemsn"); }

Answer: Two lines with Cisco Systems will be printed.

The following variable is available in file1.c, who can access it? static int average;

Answer: all the functions in the file1.c can access the variable.

What is a base class?

Base class is the most generalized class in a class structure. Most applications have such root classes. In Java, Object is the base class for all classes.

What is meant by Binding?

Binding denotes association of a name with a class.

How do you link a C++ program to C functions?

By using the extern "C" linkage specification around the C function declarations.

What is collaboration?

Collaboration is a process whereby several objects cooperate to provide some higher level behavior.

What is an Object?

Object is an instance of a class. It has state, behavior and identity. It is also called as an instance of a class.

What is a constructor?

Constructor is an operation that creates an object and/or initializes its state.

What is default Constructor?

Constructor with no arguments or all the arguments has default values. In Above Question Test() is a default constructor

What is a destructor?

Destructor is an operation that frees the state of an object and/or destroys the object itself. In Java, there is no concept of destructors. Its taken care by the JVM.

'What is meant by Encapsulation?

Encapsulation is the process of compartmentalizing the elements of an abstraction that defines the structure and behavior. Encapsulation helps to separate the contractual interface of an abstraction and implementation.

List out some of the OODBMS available. .

GEMSTONE/OPAL of Gemstone systems, ONTOS of Ontos, Objectivity of Objectivity Inc, Versant of Versant object technology, Object store of Object Design, ARDENT of ARDENT software, POET of POET software

What is an orthogonal base class?

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.

What is an Interface?

Interface is an outside view of a class or object which emphasizes its abstraction while hiding its structure and secrets of its behavior.

Assume I have a linked list contains all of the alphabets from A to Z . I want to find the letter Q in the list, how do you perform the search to find the Q ?

In a linked list, we only know about the header and other elements are invisible unless we go through the node one by one. Since we have go through every single node to find Q , the search time for a linked list is linear which is O (N).

What is an incomplete type?

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. 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.

What is meant by Inheritance?

Inheritance is a relationship among classes, wherein one class shares the structure or behavior defined in another class. This is called Single Inheritance. If a class shares the structure or behavior from multiple classes, then it is called Multiple Inheritance. Inheritance defines "is-a" hierarchy among classes in which one subclass inherits from one or more generalized superclasses

Define Namespace

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 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.

What is a Null object?

It is an object of some class whose purpose is to indicate that a real object of that classdoes 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.

Explain the scope resolution operator.

It permits a program to reference an identifier in the global scope that has been hidden by another identifier with the same name in the local scope.

Which recursive sorting technique always makes recursive calls to sort subarrays that are about half size of the original array?

Mergesort always makes recursive calls to sort subarrays that are about half size of the original array, resulting in O(n log n) time

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.

Define Modularity?

Modularity is the property of a system that has been decomposed into a set of cohesive and loosely coupled modules

What is meant by Object Oriented Programming?

OOP is a method of programming in which programs are organized as cooperative collections of objects. Each object is an instance of a class and each class belong to a hierarchy.

List out some of the object-oriented methodologies.

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).

What are proxy objects?

Objects that stand for other objects are called proxy objects or surrogates. template <class t=""> 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; };

What is meant by Persistence?

Persistence is the property of an object by which its existence transcends space and time.

Define precondition and post-condition 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. 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.

What is meant by static binding?

Static binding is a binding in which the class association is made during compile time. This is also called as Early binding.

Can you be bale to identify between Straight- through and Cross- over cable wiring? and in what case do you use Straight- through and Cross-over? (Asked by Cisco system people)

Straight-through is type of wiring that is one to to one connection Cross- over is type of wiring which those wires are got switched We use Straight-through cable when we connect between NIC Adapter and Hub. Using Cross-over cable when connect between two NIC Adapters or sometime between two hubs

What is a subclass?

Subclass is a class that inherits from one or more classes

Anything wrong with this code?

T *p = new T[10]; delete p; Note: Incorrect replies: No, everything is correct", Only the first element of the array will be deleted", The entire array will be deleted, but only the first element destructor will be called"

Differentiate between a template class and class template.

Template class: A generic definition or a parameterized 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.

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

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

What are the differences between a C++ struct and C++ class?

The default member and base-class access specifiers are different.

Why are arrays usually processed with for loop?

The real power of arrays comes from their facility of using an index variable to traverse the array, accessing each element with the same expression a[i]. All the is needed to make this work is a iterated statement in which the variable i serves as a counter, incrementing from 0 to a.length -1. That is exactly what a loop does.

How many ways are there to initialize an int with a constant?

Two. There are two formats for initializers in C++ as shown in the example that follows. The first format uses the traditional C notation. The second format uses constructor notation. int foo = 123; int bar (123);

WHat will be the result of the following code? #define TRUE 0 // somecode. while(TRUE) { // somecode }

This will not go into the loop as TRUE is defined as 0.

What is Pure-Polymorphism?

When a method is declared as abstract/virtual method in a base class and which is overridden in a base class. If we create a variable of a type of a base class and assign an object of a derived class to it, it will be decided at a run time, which implementation of a method is to be called. This is known as PurePolymorphism or Late-Binding.

How do you find out if a linked-list has an end? (i.e. the list is not a cycle)

You can find out by using 2 pointers. One of them goes 2 nodes each time. The second one goes at 1 nodes 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.

Suppose that data is an array of 1000 integers. Write a single function call that will sort the 100 elements data [222] through data [321].

quicksort ((data + 222), 100);

What is a superclass?

superclass is a class from which another class inherits.

How do you write a function that can reverse a linked-list? (Cisco System)

void reverselist(void) { if(head==0) return; if(head->next==0) return; if(head->next==tail) { www.freshersparadise.com head->next = 0; tail->next = head; } else { node* pre = head; node* cur = head->next; node* curnext = cur->next; head->next = 0; cur->next = head; for(; curnext!=0; ) { cur->next = pre; pre = cur; cur = curnext; curnext = curnext->next; } curnext->next = cur; } }