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.
Write basic concepts of OOPS?
Following are the concepts of OOPS and are as follows:
Abstraction.
Encapsulation.
Inheritance.
Polymorphism.
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 is an object?
An object is an instance of a class. It has its own state, behavior, and identity.
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 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 Inheritance?
Inheritance is a concept where one class shares the structure and behavior defined in another class. If inheritance applied on one class is called Single Inheritance, and if it depends on multiple classes, then it is called multiple Inheritance.
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.
Define a 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 same as class name.
A constructor must have no return type.
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.
Friend can be declared anywhere in the class declaration, and it cannot be affected by access control keywords like private, public or protected.
What is function overloading?
Function overloading an as a normal function, but it can perform different tasks. 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.
Example
void add(int& a, int& b);
void add(double& a, double& b);
void add(struct bob& a, struct bob& b);
What is operator overloading?
Operator overloading is a function where different operators are applied and depends on the arguments. Operator,-,* can be used to pass through the function, and it has their own precedence to execute
What is an abstract class?
An abstract class is a class which cannot be instantiated. Creation of an object is not possible with an abstract class, but it can be inherited. An abstract class can contain only Abstract method. Java allows only abstract method in abstract class while for other languages allow non-abstract method as well.
What is method overriding?
Method overriding is a feature that allows a subclass to provide the implementation of a method that overrides in the main class. This will overrides the implementation in the superclass by providing the same method name, same parameter and same return type.
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 same value in the same class itself.
Overriding is the same method names with same arguments and return types associated with the class and its child class.
Difference between 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, and an object doesn’t have sub-objects.
What is an abstraction?
Abstraction is a good feature of OOPS, and it shows only the necessary details to the client of an object. Means, it shows only required details for an object, not the inner constructors, of an object. Example – When you want to switch On television, it not necessary to show all the functions of TV. Whatever is required to switch on TV will be showed by using abstract class.
What are access modifiers?
Access modifiers determine the scope of the method or variables that can be accessed from other various objects or classes. There are 5 types of access modifiers, and they are as follows:
Private.
Protected.
Public.
Friend.
Protected Friend.
What are the various types of constructors?
There are three various types of constructors, and they are as follows:
– 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 are all the operators that cannot be overloaded?
Following are the operators that cannot be overloaded -.
Scope Resolution (:: )
Member Selection (.)
Member selection through a pointer to function (.*)
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 a copy constructor?
This is a special constructor for creating a new object as a copy of an existing object. There will always be only one copy constructor that can be either defined by the user or the system.
References:
https://www.geeksforgeeks.org/commonly-asked-oop-interview-questions/
https://www.journaldev.com/12492/oops-interview-questions-answers
https://www.springpeople.com/blog/30-oops-interview-questions-and-answers-2018/
https://medium.com/@yannmjl/object-oriented-programming-concepts-in-simple-english-3db22065d7d0