Object Oriented Programming, Study notes of Software Development

Download Object Oriented Programming and more Study notes Software Development in PDF only on Docsity! 1 Object-oriented programming (OOP) is a computer science term used to characterize a programming language that began development in the 1960’s. The term ‘object-oriented programming’ was originally coined by Xerox PARC to designate a computer application that describes the methodology of using objects as the foundation for computation. By the 1980’s, OOP rose to prominence as the programming language of choice, exemplified by the success of C++. Currently, OOPs such as Java, J2EE, C++, C#, Visual Basic.NET, Python and JavaScript are popular OOP programming languages that any career- oriented Software Engineer or developer should be familiar with. OOP is widely accepted as being far more flexible than other computer programming languages. OOPs use three basic concepts as the fundamentals for the programming language: classes, objects and methods. Additionally, Inheritance, Abstraction, Polymorphism, Event Handling and Encapsulation. Common Questions & Answers 1) 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. 2) What is a Class? Class is a template for a set of objects that share a common structure and a common behavior. 3) 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. 4) 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. 5) What are the core OOP’s concepts? Abstraction, Encapsulation, Inheritance and Polymorphism are the core OOP’s concepts. 6) 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. 7) 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. 8) 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. Object Oriented Programming (Interview Questions & Answers) Collected from different websites. Use for non-commercial purpose. Sohail Basheer Lecturer- Computer Science (visiting) Department of Computer Science & IT (Evening Program) Federal Urdu University Arts, Science & Technology Gulshan Campus Karachi 2 9) What is meant by Polymorphism? Polymorphism literally means taking more than one form. Polymorphism is a characteristic of being able to assign a different behavior or value in a subclass, to something that was declared in a parent class. 10) 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. 11) 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. 12) 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. 13) What is a subclass? Subclass is a class that inherits from one or more classes 14) What is a superclass? superclass is a class from which another class inherits. 15) What is a constructor? Constructor is an operation that creates an object and/or initializes its state. 16) 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. 17) What is meant by Binding? Binding denotes association of a name with a class. 18) 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. 19) 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. 20) Define Modularity? Modularity is the property of a system that has been decomposed into a set of cohesive and loosely coupled modules. 21) What is meant by Persistence? Persistence is the property of an object by which its existence transcends space and time. 22) What is collaboration? Collaboration is a process whereby several objects cooperate to provide some higher level behavior. 5 Test t2(t1); // calling Test copy constructor Test t2 = t1;// calling Test copy constructor Copy constructors are called in following cases: • when a function returns an object of that class by value • when the object of that class is passed by value as an argument to a function • when you construct an object based on another object of the same class • When compiler generates a temporary object 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? A special method called by GC. just before object is being reclaimed by GC. How a base class method is hidden? Hiding a base class method by declaring a method in derived class with keyword new. This will override the base class method and old method will be suppressed. What Command is used to implement properties in C#? get & set access modifiers are used to implement properties in c#. What is method overloading? Method overloading is having methods with same name but carrying different signature, this is useful when you want a method to behave differently depending upon a data passed to it. Can constructors have parameters? Yes, constructors can have parameters. so we can overload it. What are Static Assembly and Dynamic Assembly? Static assemblies can include .NET Framework types (interfaces and classes) as well as resources for the assembly (bitmaps, JPEG files, resource files, and so forth). Static assemblies are stored on disk. Dynamic assemblies run directly from memory and are not saved to disk before execution. Describe the functionality of an assembly. It is the smallest unit that has version control. All types and resources in the same assembly are versioned as a unit and support side by side execution. Assemblies contain the metadata and other identities which allow the common language runtime to execute. They are the boundaries providing the type check. They the unit where security permissions are requested and granted. What is serialization? Serialization is the process of converting an object into a stream of bytes. De-serialization is the opposite process of creating an object from a stream of bytes. Serialization/De-serialization is mostly used to transport objects (e.g. during remoting), or to persist objects (e.g. to a file or database). There are two separate mechanisms provided by the .NET class library for serialization - XmlSerializer and 6 SoapFormatter and BinaryFormatter. Microsoft uses XmlSerializer for Web Services, and uses SoapFormatter/BinaryFormatter for remoting. What are C++ storage classes? auto:the default. Variables are automatically created and initialized when they are defined and are destroyed at the end of the block containing their definition(when they are out of scope). They are not visible outside that block auto int x; int y; Both are same statement. auto is defalt register:a type of auto variable. a suggestion to the compiler to use a CPU register for performance(Generally Used in loops) static:a variable that is known only within the function that contains its definition but is never destroyed and retains its value between calls to that function. It exists from the time the program begins execution void example() { static int x = 0; // static variable x++; cout << x <<endl; } If this function is called 10 times, the output will be 1,2,3,4..etc., The value of the variable x is preserved through function calls. If this static variable is declared as a member of a class, then it will preserve the value for all the objects of the class.i.e, one copy of this data variable will be shared by all objects of the class Note: if we will declare variable like this int x=0; in the above example. then it will print 1 every it will be called extern:a static variable whose definition and placement is determined when all object and librar modules are combined (linked) to form the executable code file. It can be visible outside the file where it is defined. What is RTTI? Runtime type identification (RTTI) lets you find the dynamic type of an object when you have only a pointer or a reference to the base type. RTTI is the official way in standard C++ to discover the type of an object and to convert the type of a pointer or reference (that is, dynamic typing). The need came from practical experience with C++. RTTI replaces many homegrown versions with a solid, consistent approach. What is friend function? As the name suggests, the function acts as a friend to a class. As a friend of a class, it can access its private and protected members. A friend function is not a member of the class. But it must be listed in the class definition. 7 What is a scope resolution operator? A scope resolution operator (::), can be used to define the member functions of a class outside the class. What do you mean by pure virtual functions? A pure virtual member function is a member function that the base class forces derived classes to provide. Normally these member functions have no implementation. Pure virtual functions are equated to zero. class Shape { public: virtual void draw() = 0; }; What is the difference between declaration and definition? The declaration tells the compiler that at some later point we plan to present the definition of this declaration. E.g.: void stars () //function declaration The definition contains the actual implementation. E.g.: void stars () { for(int j=10; j > =0; j--) //function body cout << *; cout << endl; } What are the advantages of inheritance? It permits code reusability. Reusability saves time in program development. It encourages the reuse of proven and debugged high-quality software, thus reducing problem after a system becomes functional. Association Association is a relationship where all object have their own lifecycle and there is no owner. Let’s take an example of Teacher and Student. Multiple students can associate with single teacher and single student can associate with multiple teachers but there is no ownership between the objects and both have their own lifecycle. Both can create and delete independently. Aggregation Aggregation is a specialize form of Association where all object have their own lifecycle but there is ownership and child object can not belongs to another parent object. Let’s take an example of Department and teacher. A single teacher can not belongs to multiple departments, but if we delete the department teacher object will not destroy. We can think about “has-a” relationship.