(Paper) OOPS INTERVIEW QUESTIONS Set-2

OOPS INTERVIEW QUESTIONS Set-2

 

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.

Object Oriented : Essentials and History
An object-oriented programming language (also called an OO language) is one that allows or encourages, to some degree, object-oriented programming methods.

Simula (1967) is generally accepted as the first language to have the primary features of an object-oriented language. It was created for making simulation programs, in which what came to be called objects were the most important information representation. Smalltalk (1972 to 1980) is arguably the canonical example, and the one with which much of the theory of object-oriented programming was developed.

OO languages can be grouped into several broad classes, determined by the extent to which they support all features and functionality of object-orientation and objects: classes, methods, polymorphism, inheritance, and reusability.

* Languages called ?pure? OO languages, because everything in them is treated consistently as an object, from primitives such as characters and punctuation, all the way up to whole classes, prototypes, blocks, modules, etc. They were designed specifically to facilitate, even enforce, OO methods. Examples: Smalltalk, Eiffel, Ruby.
* Languages designed mainly for OO programming, but with some procedural elements. Examples: Java, Python.
* Languages that are historically procedural languages, but have been extended with some OO features. Examples: C++, Fortran 2003, Perl.
* Languages with most of the features of objects (classes, methods, inheritance, reusability), but in a distinctly original, even elegant, form. Examples: Oberon, and successor Oberon-2.
* Languages with abstract data type support, but not all features of object-orientation, sometimes called object-based languages. Examples: Modula-2 (with excellent encapsulation and information hiding), Pliant.

Inheritance and polymorphism are usually used to reduce code bloat. Abstraction and encapsulation are used to increase code clarity, quite independent of the other two traits.

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.

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);
}

~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.

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 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;
}
};

 

What do u meant by ?SBI? of an object?
SBI stands for State, Behavior and Identity. Since every object has the above three.

State: It is just a value to the attribute of an object at a particular time.
Behaviour:It describes the actions and their reactions of that object.Identity:
An object has an identity that characterizes its own existence. The identity makes it possible to distinguish any object in an unambiguous way, and independently from its state.

Differentiate the class representation of Booch, Rumbaugh and UML?
If you look at the class representation of Rumbaugh and UML, It is some what similar and both are very easy to draw.

Whether unified method and unified modeling language are same or different?
Unified method is convergence of the Rumbaugh and Booch. Unified modeling lang. is the fusion of Rumbaugh, Booch and Jacobson as well as Betrand Meyer (whose contribution is ?sequence diagram?). Its? the superset of all the methodologies.

What is meant by ?method-wars??
Before 1994 there were different methodologies like Rumbaugh, Booch, Jacobson, Meyer etc who followed their own notations to model the systems. The developers were in a dilemma to choose the method which best accomplishes their needs. This particular span was called as ?method-wars?

Differentiate Aggregation and containment?
Aggregation is the relationship between the whole and a part. We can add/subtract some properties in the part (slave) side. It won?t affect the whole part. Best example is Car, which contains the wheels and some extra parts. Even though the parts are not there we can call it as car. But, in the case of containment the whole part is affected when the part within that got affected. The human body is an apt example for this relationship. When the whole body dies the parts (heart etc) are died.

Why generalization is very strong?
Even though Generalization satisfies Structural, Interface, Behaviour properties. It is mathematically very strong, as it is Antisymmetric and Transitive. Antisymmetric: employee is a person, but not all persons are employees. Mathematically all As? are B, but all Bs? not A.

What do you meant by static and dynamic modeling?
Static modeling is used to specify structure of the objects that exist in the problem domain. These are expressed using class, object and USECASE diagrams. But Dynamic modeling refers representing the object interactions during runtime. It is represented by sequence, activity, collaboration and statechart diagrams

What is meant by software development method?
Software development method describes how to model and build software systems in a reliable and reproducible way. To put it simple, methods that are used to represent ones? thinking using graphical notations.

What do you meant by active and passive objects?
Active objects are one which instigate an interaction which owns a thread and they are responsible for handling control to other objects. In simple words it can be referred as client.
Passive objects are one, which passively waits for the message to be processed. It waits for another object that requires its services. In simple words it can be referred as server.

Differentiate persistent & non-persistent objects?
Persistent refers to an object?s ability to transcend time or space. A persistent object stores/saves its state in a permanent storage system with out losing the information represented by the object.
A non-persistent object is said to be transient or ephemeral. By default objects are considered as non-persistent.

What are the steps involved in designing?
Before getting into the design the designer should go through the SRS prepared by the System Analyst. The main tasks of design are Architectural Design and Detailed Design. In Architectural Design we find what are the main modules in the problem domains Detailed Design we find what should be done within each module.

What do you mean by analysis and design?
Analysis: It is the process of determining what needs to be done before how it should be done. In order to accomplish this, the developer refers the existing systems and documents. So, simply it is an art of discovery.

Design: It is the process of adopting/choosing the one among the many, which best accomplishes the users needs. So, simply, it is compromising mechanism.