OOPS

What are the various types of constructors?

- Default Constructor - With no parameters. - Parametric Constructor - With Parameters. Create a new instance of a class and also passing arguments simultaneously. - Copy Constructor - Which creates a new object as a copy of an existing object.

What is a class?

A class is simply a representation of a type of object. It is the blueprint/plan/template that describes the details of an object.

What are tokens?

A compiler recognizes a token, and it cannot be broken down into component elements. Keywords, identifiers, constants, string literals, and operators are examples of tokens. Even punctuation characters are also considered as tokens. Example: Brackets, Commas, Braces, and Parentheses.

Explain the term constructor

A constructor is a method used to initialize the state of an object, and it gets invoked at the time of object creation. Rules for constructor are: Constructor Name should be the same as a class name. A constructor must have no return type.

What is a constructor?

A constructor is a special type of method that has the same name as the class and is used to initialize objects of that class.

What is a copy constructor?

A copy constructor creates objects by copying variables from another object of the same class. The main aim of a copy constructor is to create a new object from an existing one.

What is a destructor?

A destructor is a method that is automatically invoked when an object is destroyed. The destructor also recovers the heap space that was allocated to the destroyed object, closes the files and database connections of the object, etc.

Define Destructor?

A destructor is a method which is automatically called when the object is made of scope or destroyed. Destructor name is also same as class name but with the tilde symbol before the name.

What is a finally block?

A finally block consists of code that is used to execute important code such as closing a connection, etc. This block executes when the try block exits. It also makes sure that finally block executes even in case some unexpected exception is encountered.

What is a friend function?

A friend function is a friend of a class that is allowed to access to Public, private, or protected data in that same class. If the function is defined outside the class cannot access such information. A friend can be declared anywhere in the class declaration, and it cannot be affected by access control keywords like private, public, or protected.

What are the different types of arguments?

A parameter is a variable used during the declaration of the function or subroutine, and arguments are passed to the function body, and it should match with the parameter defined. There are two types of Arguments. Call by Value - Value passed will get modified only inside the function, and it returns the same value whatever it is passed into the function. Call by Reference - Value passed will get modified in both inside and outside the functions and it returns the same or different value.

What is a pure virtual function?

A pure virtual function is a function which can be overridden in the derived class but cannot be defined. A virtual function can be declared as Pure by using the operator =0.

What is a try/ catch block?

A try/ catch block is used to handle exceptions. The try block defines a set of statements that may lead to an error. The catch block basically catches the exception.

What is a final variable?

A variable whose value does not change. It always refers to the same object by the property of non-transversity.

What is a virtual function?

A virtual function is a member function of a class, and its functionality can be overridden in its derived class. This function can be implemented by using a keyword called virtual, and it can be given during function declaration. A virtual function can be declared using a token(virtual) in C++. It can be achieved in C/Python Language by using function pointers or pointers to function.

Write basic concepts of OOPS?

Abstraction Encapsulation Inheritance Polymorphism

What is an abstraction?

Abstraction is a useful feature of OOPS, and it shows only the necessary details to the client of an object. Meaning, it shows only required details for an object, not the inner constructors, of an object. Example - When you want to switch on the television, it is not necessary to know the inner circuitry/mechanism needed to switch on the TV. Whatever is required to switch on TV will be shown by using an abstract class.

What are the access modifiers?

Access modifiers determine the scope of the method or variables that can be accessed from other various objects or classes. There are five types of access modifiers, and they are as follows: Private Protected Public Friend Protected Friend

What is an abstract class?

An abstract class is a class that consists of abstract methods. These methods are basically declared but not defined. If these methods are to be used in some subclass, they need to be exclusively defined in the subclass.

What is an exception?

An exception is a kind of notification that interrupts the normal execution of a program. Exceptions provide a pattern to the error and transfer the error to the exception handler to resolve it. The state of the program is saved as soon as an exception is raised.

What is an Inline function?

An inline function is a technique used by the compilers and instructs to insert complete body of the function wherever that function is used in the program source code.

What is an Object?

An object is a real-world entity which is the basic unit of OOPs for example chair, cat, dog, etc. Different objects have different states or attributes, and behaviors.

What is the main difference between a class and an object?

An object is an instance of a class. Objects hold multiple information, but classes don't have any information. Definition of properties and functions can be done in class and can be used by the object. A class can have sub-classes, while an object doesn't have sub-objects.

What is static and dynamic Binding?

Binding is nothing but the association of a name with the class. Static Binding is a binding in which name can be associated with the class during compilation time, and it is also called as early Binding. Dynamic Binding is a binding in which name can be associated with the class during execution time, and it is also called as Late Binding.

How to achieve data abstraction?

Data abstraction can be achieved through: Abstract class Abstract method

What is data abstraction?

Data abstraction is a very important feature of OOPs that allows displaying only the important information and hiding the implementation details. For example, while riding a bike, you know that if you raise the accelerator, the speed will increase, but you don't know how it actually happens. This is data abstraction as the implementation details are hidden from the rider.

Declarative Programming Paradigm

Declarative programming focuses on WHAT to execute and defines program logic, but not a detailed control flow. Declarative paradigm can be further classified into:a) Logical Programming Paradigm: Logical programming paradigm is based on formal logic, which refers to a set of sentences expressing facts and rules about how to solve a problemb) Functional Programming Paradigm: Functional programming is a programming paradigm where programs are constructed by applying and composing functions.c) Database Programming Paradigm: Database programming model is used to manage data and information structured as fields, records, and files.

What is dynamic or run time polymorphism?

Dynamic or Run time polymorphism is also known as method overriding in which call to an overridden function is resolved during run time, not at the compile time. It means having two or more methods with the same name, same signature but with different implementation.

What is early and late Binding?

Early binding refers to the assignment of values to variables during design time, whereas late Binding refers to the assignment of values to variables during run time.

Which OOPS concept exposes only the necessary information to the calling functions?

Encapsulation

What is Encapsulation?

Encapsulation is an attribute of an object, and it contains all data which is hidden. That hidden data can be restricted to the members of that class. Levels are Public, Protected, Private, Internal, and Protected Internal.

What is encapsulation?

Encapsulation refers to binding the data and the code that works on that together in a single unit. For example, a class. Encapsulation also allows data-hiding as the data specified in one class is hidden from other classes.

What is exception handling?

Exception handling in Object-Oriented Programming is a very important concept that is used to manage errors. An exception handler allows errors to be thrown and caught and implements a centralized mechanism to resolve them.

What is the use of 'finalize'?

Finalize as an object method used to free up unmanaged resources and cleanup before Garbage Collection(GC). It performs memory management tasks.

What is the use of finalize method?

Finalize method helps to perform cleanup operations on the resources which are not currently used. Finalize method is protected, and it is accessible only through this class or by a derived class.

What is function overloading?

Function overloading is a regular function, but it is assigned with multiple parameters. It allows the creation of several methods with the same name which differ from each other by the type of input and output of the function.

What is Garbage Collection(GC)?

GC is an implementation of automatic memory management. The Garbage collector frees up space occupied by objects that are no longer in existence.

What are some other programming paradigms other than OOPs?

Imperative Programming Paradigm Declarative Programming Paradigm

Imperative Programming Paradigm

Imperative programming focuses on HOW to execute program logic and defines control flow as statements that change a program state. This can be further classified as:a) Procedural Programming Paradigm: Procedural programming specifies the steps a program must take to reach the desired state, usually read in order from top to bottom.b) Object-Oriented Programming or OOP: Object-oriented programming (OOP) organizes programs as objects, that contain some data and have some behavior.c) Parallel Programming: Parallel programming paradigm breaks a task into subtasks and focuses on executing them simultaneously at the same time.

What is Inheritance?

Inheritance is a concept where one class shares the structure and behavior defined in another class. If Inheritance applied to one class is called Single Inheritance, and if it depends on multiple classes, then it is called multiple Inheritance.

Which OOPS concept is used as a reuse mechanism?

Inheritance is the OOPS concept that can be used as a reuse mechanism.

What is an interface?

It is a concept of OOPs that allows you to declare methods without defining them. Interfaces, unlike classes, are not blueprints because they do not contain detailed instructions or actions to be performed. Any class that implements an interface defines the methods of the interface.

What does the keyword virtual represented in the method definition?

It means we can override the method.

What are some major Object Oriented Programming languages?

Java C++ Javascript Python PHP

What are manipulators?

Manipulators are the functions which can be used in conjunction with the insertion (<<) and extraction (>>) operators on an object. Examples are endl and setw.

What is method overloading?

Method overloading is a feature of OOPs which makes it possible to give the same name to more than one methods within a class if the arguments passed differ.

What is method overriding?

Method overriding is a feature of OOPs by which the child class or the subclass can redefine methods present in the base class or parent class. Here, the method that is overridden has the same name as well as the signature meaning the arguments passed and the return type.

Can you create an instance of an abstract class?

No. Instances of an abstract class cannot be created because it does not have a complete implementation. However, instances of subclass inheriting the abstract class can be created.

What is OOPS?

OOPS is abbreviated as Object Oriented Programming system in which programs are considered as a collection of objects. Each object is nothing but an instance of a class.

Which keyword can be used for overloading?

Operator keyword is used for overloading.

What is operator overloading?

Operator overloading refers to implementing operators using user-defined types based on the arguments passed along with it.

What is the main difference between overloading and overriding?

Overloading is static Binding, whereas Overriding is dynamic Binding. Overloading is nothing but the same method with different arguments, and it may or may not return the equal value in the same class itself. Overriding is the same method names with the same arguments and return types associated with the class and its child class.

What is Polymorphism?

Polymorphism is nothing but assigning behavior or value in a subclass to something that was already declared in the main class. Simply, polymorphism takes more than one form.

What is polymorphism?

Polymorphism refers to the ability to exist in multiple forms. Multiple definitions can be given to a single interface. For example, if you have a class named Vehicle, it can have a method named speed but you cannot define it because different vehicles have different speed. This method will be defined in the subclasses with different definitions for different vehicles.

What is the default access specifier in a class definition?

Private access specifier is used in a class definition.

What are pure virtual functions?

Pure virtual functions or abstract functions are functions that are only declared in the base class. This means that they do not contain any definition in the base class and need to be redefined in the subclass.

What is dynamic polymorphism?

Runtime polymorphism or dynamic polymorphism (dynamic binding) is a type of polymorphism which is resolved during runtime. An example of runtime polymorphism is method overriding.

What are all the operators that cannot be overloaded?

Scope Resolution (::) Member Selection (.) Member selection through a pointer to function (.*)

What are sealed modifiers?

Sealed modifiers are the access modifiers where the methods can not inherit it. Sealed modifiers can also be applied to properties, events, and methods. This modifier cannot be used to static members.

What is static polymorphism?

Static polymorphism (static binding) is a kind of polymorphism that occurs at compile time. An example of compile-time polymorphism is method overloading.

What is 'this' pointer?

THIS pointer refers to the current object of a class. THIS keyword is used as a pointer which differentiates between the current object with the global object. It refers to the current object.

What are a base class, subclass, and superclass?

The base class is the most generalized class, and it is said to be a root class. A Subclass is a class that inherits from one or more base classes. The superclass is the parent class from which another class inherits.

What is the default access modifier in a class?

The default access modifier of a class is Internal and the default access modifier of a class member is Private.

What is the difference between structure and a class?

The default access type of a Structure is public, but class access type is private. A structure is used for grouping data, whereas a class can be used for grouping data and methods. Structures are exclusively used for data, and it doesn't require strict validation, but classes are used to encapsulate and inherent data, which requires strict validation.

What is the difference between new and override?

The new modifier instructs the compiler to use the new implementation instead of the base class function. Whereas, Override modifier helps to override the base class function.

What is the super keyword?

The super keyword is used to invoke the overridden method, which overrides one of its superclass methods. This keyword allows to access overridden methods and also to access hidden members of the superclass. It also forwards a call from a constructor, to a constructor in the superclass.

What is a ternary operator?

The ternary operator is said to be an operator which takes three arguments. Arguments and results are of different data types, and it depends on the function. The ternary operator is also called a conditional operator.

What is the need for OOPs?

There are many reasons why OOPs is mostly preferred, but the most important among them are: OOPs helps users to understand the software easily, although they don't know the actual implementation. With OOPs, the readability, understandability, and maintainability of the code increase multifold. Even very big software can be easily written and managed easily using OOPs.

What are the limitations of OOPs?

Usually not suitable for small problems Requires intensive testing Takes more time to solve the problem Requires proper planning The programmer should think of solving a problem in terms of objects

What are virtual functions?

Virtual functions are functions that are present in the parent class and are overridden by the subclass. These functions are used to achieve runtime polymorphism.

How can we call the base method without creating an instance?

Yes, it is possible to call the base method without creating an instance. And that method should be "Static method." Doing Inheritance from that class.-Use Base Keyword from a derived class.

How many instances can be created for an abstract class?

Zero instances will be created for an abstract class. In other words, you cannot create an instance of an Abstract Class.