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OOP Interview Questions Answers

Question 1 : What is the difference between procedural and object-oriented programs?

Answer 1 : 1. In procedural program, programming logic follows certain procedures and the instructions are executed one after another. In OOP program, unit of program is object, which is nothing but combination of data and code. 2. In procedural program, data is exposed to the whole program whereas in OOPs program, it is accessible with in the object and which in turn assures the security of the code.

Question 2 : Does a class inherit the constructors of its superclass?

Answer 2 : A class does not inherit constructors from any of its super classes. If a class is declared without any access modifiers, where may the class be accessed? A class that is declared without any access modifiers is said to have package access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.

Question 3 : What is a modifier?

Answer 3 : 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; } };

Question 4 : When does a name clash occur?

Answer 4 : 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.

Question 5 : What is the difference between superclass and subclass?

Answer 5 : A super class is a class that is inherited whereas sub class is a class that does the inheriting.

Question 6 : What is difference between overloading and overriding?

Answer 6 : a) In overloading, there is a relationship between methods available in the same class whereas in overriding, there is relationship between a superclass method and subclass method. b) Overloading does not block inheritance from the superclass whereas overriding blocks inheritance from the superclass. c) In overloading, separate methods share the same name whereas in overriding, subclass method replaces the superclass. d) Overloading must have different method signatures whereas overriding must have same signature.  

Question 7 : Differentiate Aggregation and containment?

Answer 7 : 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.

Question 8 : How many ways can an argument be passed to a subroutine?

Answer 8 : An argument can be passed in two ways. They are Pass by Value and Passing by Reference. Passing by value: This method copies the value of an argument into the formal parameter of the subroutine. Passing by reference: In this method, a reference to an argument (not the value of the argument) is passed to the parameter.

Question 9 : Object Oriented : Essentials and History

Answer 9 : 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.

Question 10 : What do you mean by analysis and design?

Answer 10 : 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.

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