Interview Questions and Answers

• C++ is a high-performance programming language that is widely used for developing a wide range of applications, including operating systems, games, and desktop and mobile applications. It was developed as an extension of the C programming language and is known for its flexibility, efficiency, and low-level control.
• C++ is an object-oriented programming language, which means that it allows developers to define and create objects that can be used to model real-world entities. It also supports procedural programming, which means that it allows developers to write code using functions and procedures.
• One of the key features of C++ is its support for templates, which allow developers to write code that can work with any data type. This allows developers to create generic algorithms and data structures that can be used with different types of data.
• C++ is a compiled language, which means that the source code is translated into machine code that can be run directly on a computer's hardware. This makes C++ programs fast and efficient, but it also means that they can be difficult to debug and maintain.
• Overall, C++ is a powerful and popular programming language that is widely used in a variety of applications. It is known for its performance, flexibility, and low-level control, and it is a great choice for developing a wide range of applications.

• C++ has a number of advantages that have contributed to its popularity and widespread use:
• Performance: C++ is a compiled language, which means that it is translated into machine code that can be run directly on a computer's hardware. This makes C++ programs fast and efficient.
• Flexibility: C++ is a flexible language that allows developers to write code that can be used in a variety of contexts. It supports both object-oriented and procedural programming, which gives developers a lot of freedom and control over their code.
• Low-level control: C++ allows developers to interact directly with a computer's hardware, which gives them a lot of control over how their programs behave. This is particularly useful for developing systems-level programs, such as operating systems and drivers.
• Widely used: C++ is a popular and widely used programming language, which means that it has a large and active community of developers and users. This makes it easy to find resources and support for C++ programming.
• Portable: C++ programs can be compiled for a variety of different platforms, which means that they can be run on a wide range of different devices and operating systems.
• Overall, C++ is a powerful and flexible programming language that is well-suited for a wide range of applications. It is known for its performance, low-level control, and flexibility, and it is a popular choice for developing a wide range of applications.

• C and C++ are two programming languages that have a lot in common, but there are also some key differences between them.
• C is a procedural programming language that was developed in the 1970s. It is known for its simplicity and efficiency, and it is widely used for developing a variety of applications, including operating systems, compilers, and text editors.
• C++ is an object-oriented programming language that was developed as an extension of C in the 1980s. It is a high-performance language that is widely used for developing a wide range of applications, including operating systems, games, and desktop and mobile applications.
• One of the main differences between C and C++ is that C++ supports object-oriented programming, while C does not. This means that C++ allows developers to define and create objects that can be used to model real-world entities, while C does not. C++ also has a number of other features that are not present in C, including templates, exception handling, and function overloading.
• Another difference between C and C++ is that C is a procedural language, while C++ is both procedural and object-oriented. This means that C++ allows developers to write code using functions and procedures, as well as objects and classes.
• Overall, C and C++ are two closely related programming languages that have a lot in common, but there are also some key differences between them. C++ is a more powerful and flexible language than C, but it is also more complex and can be more difficult to learn and use.

• In C++, a reference is a way to refer to an object using an alias, while a pointer is a variable that stores the memory address of an object. There are a few key differences between references and pointers:
• Syntax: References are declared using the & operator, while pointers are declared using the * operator. For example, to declare a reference to an integer, you would write int &x, and to declare a pointer to an integer, you would write int *x.
• Binding: References are bound to an object when they are created, and they cannot be reassigned to refer to a different object. Pointers, on the other hand, can be reassigned to refer to different objects at any time.
• Null values: Pointers can be set to null to indicate that they are not currently pointing to an object, while references cannot be null.
• Dereferencing: To access the object that a reference refers to, you can simply use the reference variable like you would use the object itself. To access the object that a pointer points to, you must use the * operator to dereference the pointer.
• Overall, references and pointers are similar in that they both allow you to refer to an object indirectly, but there are some important differences between them in terms of syntax, binding, and how they are used.

• In object-oriented programming, a class is a template or blueprint for creating objects. It defines the properties and behaviors that objects created from the class will have, as well as the methods (functions) that can be used to manipulate those properties and behaviors.
• A class is a way to define a new data type in C++. Once a class has been defined, you can create as many objects of that class as you like. Each object is an instance of the class, and it has its own set of properties and behaviors as defined by the class.
• Here is a simple example of a class definition in C++:

class Student {
    public:
        string name;
        int age;
        void setName(string n) {
            name = n;
        }
        void setAge(int a) {
            age = a;
        }
};

In this example, the Student class has two properties (name and age) and two methods (setName and setAge). You can use this class to create objects that represent students, and you can use the methods to set the values of the name and age properties for each object. Classes are an important concept in object-oriented programming and are a key feature of C++. They allow you to define new data types and create objects that have the properties and behaviors that you need for your program.

• Object-oriented programming (OOP) is a programming paradigm that is based on the concept of "objects," which represent real-world entities and the data and behaviors associated with them. C++ is an object-oriented programming language, and it supports the following OOP concepts:
• Encapsulation: Encapsulation refers to the idea of bundling data and methods that operate on that data within a single unit, or object. In C++, you can use classes to define objects that encapsulate data and methods.
• Abstraction: Abstraction refers to the process of exposing only the essential characteristics and behaviors of an object, hiding its implementation details. In C++, you can use abstract classes and pure virtual functions to define objects that have abstract behaviors.
• Inheritance: Inheritance is the process of creating a new class that is a modified version of an existing class. The new class is called the derived class, and the existing class is the base class. In C++, you can use inheritance to create a hierarchy of classes, with derived classes inheriting properties and behaviors from their base classes.
• Polymorphism: Polymorphism refers to the ability of a single interface to be used to refer to multiple different types of objects. In C++, you can use polymorphism to write code that can work with multiple different types of objects in a uniform way.
• Overall, these OOP concepts are important for designing and implementing object-oriented programs in C++, and they allow you to create reusable and modular code that is easy to maintain and extend.

• In C++, polymorphism refers to the ability of a single interface to be used to refer to multiple different types of objects. There are two main types of polymorphism in C++:
• Static polymorphism: Static polymorphism, also known as compile-time polymorphism, refers to the ability of the compiler to determine which version of a function to use at compile time, based on the type of the arguments being passed to the function. This is achieved using function overloading, which allows you to define multiple versions of a function with the same name but different argument lists.
• Dynamic polymorphism: Dynamic polymorphism, also known as run-time polymorphism, refers to the ability of a program to determine which version of a function to use at run time, based on the type of the object being referred to. This is achieved using virtual functions, which allow you to define a base class with an abstract behavior that can be overridden by derived classes.
• Overall, these two types of polymorphism are important for creating reusable and modular code in C++, and they allow you to write code that can work with multiple different types of objects in a uniform way.

• In C++, a namespace is a declarative region that provides a way to group related identifiers (names) together. Namespaces are used to avoid name collisions that can occur when two or more identifiers have the same name but are used in different contexts.
• For example, consider the following code:

#include <iostream>

namespace MyApp {
    int x = 10;
}
        
namespace MyLib {
    int x = 20;
}
        
int main() {
    using namespace MyApp;
    std::cout << x << std::endl;
    return 0;
}

In this code, there are two namespaces: MyApp and MyLib. Both namespaces define an x variable, but they are in different namespaces, so there is no name collision. In the main function, the using namespace directive is used to bring the MyApp namespace into the current scope, so that the x variable from MyApp can be accessed directly. Namespaces are a useful way to organize and manage the names in your code, and they can help to avoid conflicts and improve the readability and maintainability of your code.

• The using namespace directive in C++ allows you to bring all the names defined in a namespace into the current scope, so that you can use them directly without having to qualify them with the namespace name.
• For example, consider the following code:

#include <iostream>
                            
namespace MyApp {
    int x = 10;
}
        
int main() {
    using namespace MyApp;
    std::cout << x << std::endl;
    return 0;
}

In this code, the using namespace MyApp directive brings all the names defined in the MyApp namespace into the current scope, so that you can use the x variable without having to qualify it with the MyApp namespace name. The using namespace directive can be useful when you have a lot of names defined in a namespace and you want to use them all frequently in your code. It can save you from having to type the namespace name repeatedly and can make your code more readable and easier to write. However, it is generally considered a good practice to use the using namespace directive sparingly, as it can lead to name collisions and other problems if used excessively. Instead, it is often better to use the using directive to bring individual names into the current scope, or to fully qualify the names with the namespace name when they are used.

• In object-oriented programming, an object is a self-contained entity that represents a real-world entity or concept. Objects have properties (data) and behaviors (methods) that are associated with them, and they are used to model and represent the entities or concepts that are relevant to your program.
• For example, you might define a Student object to represent a student in a school. The Student object might have properties such as name, age, and grade level, and it might have behaviors such as enrolling in classes and earning grades.
• To create an object in C++, you first define a class that specifies the properties and behaviors of the object. Then you can use the class to create objects as needed. For example:

class Student {
    public:
      string name;
      int age;
      void setName(string n) {
        name = n;
      }
      void setAge(int a) {
        age = a;
      }
  };
  
int main() {
    Student s1;
    s1.setName("Alice");
    s1.setAge(18);
    return 0;
}

In this example, the Student class is defined with two properties (name and age) and two methods (setName and setAge). The main function creates an object of the Student class called s1, and it uses the setName and setAge methods to set the values of the name and age properties for the object. Overall, objects are an important concept in object-oriented programming, and they are used to represent and model real-world entities and concepts in a program.

• In C++, access specifiers are keywords that are used to specify the visibility and accessibility of class members (properties and methods). There are three access specifiers in C++:
• public: Members that are declared public are visible and accessible from anywhere within the program. This means that they can be accessed and modified by any code that has a reference to the object.
• private: Members that are declared private are only visible and accessible from within the class in which they are defined. They cannot be accessed or modified by code outside the class.
• protected: Members that are declared protected are only visible and accessible from within the class in which they are defined, and from derived classes (classes that inherit from the class). They cannot be accessed or modified by code outside the class or its derived classes.
• Access specifiers are an important concept in C++ and are used to control the visibility and accessibility of class members. They allow you to specify which members can be accessed and modified by different parts of your program, and they help to ensure that your code is well-organized and maintainable.

• Object-oriented programming (OOP) is a programming paradigm that is based on the concept of "objects," which represent real-world entities and the data and behaviors associated with them. OOP is centered around the idea that programs should be built using objects that represent the entities being modeled, rather than using a procedural approach that focuses on the steps being followed.
• OOP languages, such as C++, provide support for creating and using objects, and they typically include features such as classes, inheritance, and polymorphism to support object-oriented programming.
• One of the key benefits of OOP is that it allows you to create reusable and modular code. By organizing your code into objects that represent real-world entities, you can create a set of building blocks that can be used and reused in different contexts. This can make your code easier to maintain and extend, and it can help you to build more complex and scalable programs.
• Overall, OOP is a popular and widely-used programming paradigm that is well-suited for a wide range of applications. It is known for its flexibility, modularity, and reusability, and it is a powerful tool for building complex and scalable programs.

• new and malloc are both functions that are used to allocate memory dynamically at run time in C++ and C. However, there are some key differences between them:
• Syntax: new is a C++ operator, while malloc is a function in the C standard library. This means that new is used differently than malloc, and it has a different syntax.
• Type safety: new is type-safe, which means that it ensures that the type of the object being created is correct. malloc, on the other hand, does not perform any type checking, so it is possible to create an object of the wrong type if you are not careful.
• Memory initialization: new initializes the memory that it allocates to the default value for the type being created, while malloc does not initialize the memory it allocates.
• Exception handling: new can throw an exception if it is unable to allocate the requested memory, while malloc returns a null pointer if it is unable to allocate the requested memory.
• Overall, new and malloc are similar in that they both allow you to allocate memory dynamically at run time, but there are some important differences between them in terms of syntax, type safety, memory initialization, and exception handling.

• In C++, a friend function is a function that is declared as a friend of a class. A friend function is not a member of the class, but it has access to the private and protected members of the class.
• Friend functions are typically used in situations where it is necessary to provide a non-member function with access to the private and protected members of a class. They are declared using the friend keyword, followed by the function prototype.
• Here is an example of a class with a friend function:

class MyClass {
    private:
      int x;
    public:
      void setX(int v) {
        x = v;
      }
      friend void printX(MyClass &c);
};
  
void printX(MyClass &c) {
    std::cout << c.x << std::endl;
}
  
int main() {
    MyClass c;
    c.setX(10);
    printX(c);
    return 0;
}

In this example, the MyClass class has a private x member and a public setX method. The printX function is declared as a friend of MyClass, so it has access to the private x member. The main function creates an object of the MyClass class and uses the setX method to set the value of the x member. Then it calls the printX function, which is able to access and print the value of the x member. Friend functions are a useful feature of C++, and they can be used to provide non-member functions with access to the private and protected members of a class when necessary. However, they should be used sparingly, as they can break the encapsulation of the class and make the code more difficult to understand and maintain.

• In C++, a friend class is a class that is declared as a friend of another class. A friend class has access to the private and protected members of the class that it is a friend of.
• Friend classes are typically used in situations where it is necessary to provide one class with access to the private and protected members of another class. They are declared using the friend keyword, followed by the class name.
• Here is an example of two classes that are friends:

class MyClass1 {
    private:
      int x;
    public:
      void setX(int v) {
        x = v;
      }
      friend class MyClass2;
};
  
class MyClass2 {
   public:
    void printX(MyClass1 &c) {
      std::cout << c.x << std::endl;
    }
};
  
int main() {
    MyClass1 c1;
    MyClass2 c2;
    c1.setX(10);
    c2.printX(c1);
    return 0;
}

In this example, the MyClass1 class has a private x member and a public setX method. The MyClass2 class is declared as a friend of MyClass1, so it has access to the private x member. The main function creates objects of the MyClass1 and MyClass2 classes, and it uses the setX method of MyClass1 to set the value of the x member. Then it calls the printX method of MyClass2, which is able to access and print the value of the x member. Friend classes are a useful feature of C++, and they can be used to provide one class with access to the private and protected members of another class when necessary. However, they should be used sparingly, as they can break the encapsulation of the classes and make the code more difficult to understand and

• In C++, a virtual function is a member function of a class that can be overridden by derived classes (classes that inherit from the class). Virtual functions allow you to define a base class with an abstract behavior that can be modified by derived classes, and they are an important feature of object-oriented programming.
• Virtual functions are declared using the virtual keyword, followed by the function prototype. They are typically declared in the base class, and they are implemented in the base class or in derived classes.
• Here is an example of a virtual function in C++:

class Shape {
    public:
     virtual double area() = 0;
};
   
class Circle : public Shape {
    private:
    double radius;
    public:
     Circle(double r) : radius(r) {}
     double area() {
       return 3.14 * radius * radius;
    }
};
   
int main() {
    Circle c(10);
    std::cout << c.area() << std::endl;
    return 0;
}
   

• In C++, a destructor is a special member function of a class that is executed when an object of the class goes out of scope or is deleted. Destructors are used to release resources that are allocated by the object, such as memory, file handles, or network connections.
• A destructor is a member function with the same name as the class, preceded by a tilde (~). It does not have any return type or parameters, and it is called automatically when the object is destroyed.
• Here is an example of a class with a destructor:

class MyClass {
    private:
     int *p;
    public:
     MyClass(int size) {
       p = new int[size];
     }
     ~MyClass() {
       delete[] p;
     }
};
   
int main() {
    MyClass c(10);
    return 0;
}

In this example, the MyClass class has a constructor that allocates an array of integers on the heap, and a destructor that releases the memory allocated by the array. When an object of MyClass is created in the main function, the constructor is called to allocate the memory for the array. When the object goes out of scope at the end of the main function, the destructor is called to release the memory.

• In C++, overloading refers to the ability to define multiple functions with the same name but different argument lists. This allows you to create multiple versions of a function that can be called with different sets of arguments, and the correct version of the function will be called based on the types and number of arguments being passed.
• Overloading is a useful feature of C++ that allows you to create more flexible and reusable code. It allows you to write functions that can be used in different contexts, and it can make your code easier to read and understand.
• Here is an example of function overloading in C++:

#include <iostream>

void print(int x) {
    std::cout << "The value is: " << x << std::endl;
}
    
void print(double x) {
    std::cout << "The value is: " << x << std::endl;
}
    
void print(std::string x) {
    std::cout << "The value is: " << x << std::endl;
}
    
int main() {
    print(10);
    print(3.14);
    print("hello");
    return 0;
}

• In C++, function overriding refers to the ability of a derived class to redefine or override a virtual function that is inherited from a base class. Function overriding allows you to define a base class with an abstract behavior that can be modified by derived classes, and it is an important feature of object-oriented programming.
• To override a function in C++, you define a new version of the function in the derived class with the same name, return type, and parameter list as the function in the base class. The new function is then called instead of the base class function when it is called on an object of the derived class.
• Here is an example of function overriding in C++:

#include <iostream>
                            
class Shape {
    public:
        virtual double area() = 0;
    };
                                
class Circle : public Shape {
    private:
        double radius;
    public:
        Circle(double r) : radius(r) {}
    double area() {
        return 3.14 * radius * radius;
    }
};
                                
int main() {
    Circle c(10);
    std::cout << c.area() << std::endl;
    return 0;
}
                           

In this example, the Shape class has a pure virtual function called area. The Circle class is a derived class of Shape, and it overrides the area function by defining a new version of the function that calculates and returns the area of a circle based on the radius. When the area function is called on an object of the Circle class, the overridden version of the function is called, rather than the version in the base class.

• In C++, a constructor is a special member function of a class that is executed when an object of the class is created. Constructors are used to initialize the data members of the object and to allocate resources that the object needs.
• A constructor is a member function with the same name as the class, and it does not have a return type (not even void). It can have parameters, and it is called automatically when an object of the class is created.
• Here is an example of a class with a constructor:

class MyClass {
    private:
     int x;
    public:
     MyClass(int v) {
       x = v;
    }
};
   
int main() {
    MyClass c(10);
    return 0;
}

In this example, the MyClass class has a single data member called x, and a constructor that takes an integer parameter. When an object of MyClass is created in the main function, the constructor is called with the value 10, and it initializes the x member to this value. Constructors are an important feature of C++, and they are used to initialize the data members of an object and to allocate resources that the object needs. They are called automatically when an object is created, and they can make it easier to create and initialize objects in your code.

• In C++, both struct and class are user-defined types that can be used to define new data types. However, there are some key differences between them:
• Default access specifiers: In a struct, the default access specifier for members is public, while in a class, the default access specifier is private. This means that members of a struct are automatically visible and accessible from anywhere within the program, while members of a class are only visible and accessible from within the class or from derived classes.
• Syntax: The syntax for defining a struct and a class is the same, but the struct keyword is used to define a struct, while the class keyword is used to define a class.
• Usage: struct and class can be used in similar ways, but they are often used for different purposes. struct is generally used to define simple data types that do not have any complex behavior, while class is used to define more complex data types that may have both data and behavior.
• Overall, struct and class are similar in that they are both user-defined types that can be used to define new data types in C++. However, they differ in terms of the default access specifiers for their members, and they are often used for different purposes.

• In C++, a class template is a type of class that is defined with a generic type parameter. Class templates allow you to define a class that can work with different types of data, and they are a useful feature of C++ that can help you to write more flexible and reusable code.
• Class templates are defined using the template keyword, followed by the template parameter list and the class definition. The template parameter list specifies the types that the class can be instantiated with, and the class definition specifies the data members and member functions of the class.
• Here is an example of a class template:

template <typename T>
    class MyClass {
     private:
      T x;
     public:
      MyClass(T v) : x(v) {}
      T getX() {
        return x;
      }
      void setX(T v) {
        x = v;
      }
    };
    
int main() {
    MyClass <int> c1(10);
    MyClass <double> c2(3.14);
    std::cout << c1.getX() << std::endl;
    std::cout << c2.getX() << std::endl;
    return 0;
}

In this example, the MyClass class is defined with a template parameter T, which represents the type of the data member x. The MyClass class has a constructor that initializes the x member, and getter and setter functions for the x member. The main function instantiates two objects of the MyClass class, one with int as the template parameter and one with double as the template parameter. The objects can then be used to store and retrieve values of the corresponding types.

• In C++, function overloading refers to the ability to define multiple functions with the same name but different argument lists, while operator overloading refers to the ability to define new meanings for existing operators when they are used with user-defined types.
• Here are some key differences between function overloading and operator overloading:
• Syntax: Function overloading is done by defining multiple functions with the same name but different argument lists, while operator overloading is done by defining member functions or non-member functions with the operator keyword followed by the operator symbol.
• Purpose: Function overloading is used to create multiple versions of a function that can be called with different sets of arguments, while operator overloading is used to redefine the behavior of existing operators when they are used with user-defined types.
• Restrictions: Function overloading has few restrictions, and you can define as many overloaded versions of a function as you need. Operator overloading has more restrictions, and you can only overload a limited set of operators in specific ways.
• Overall, function overloading and operator overloading are both useful features of C++ that allow you to define new behavior for existing constructs. Function overloading is used to create multiple versions of a function that can be called with different sets of arguments, while operator overloading is used to redefine the behavior of existing operators when they are used with user-defined types.

• In C++, a virtual destructor is a destructor that is declared with the virtual keyword. A virtual destructor is used to ensure that the correct version of the destructor is called when an object of a derived class is deleted.
• Virtual destructors are particularly important when you are working with classes that have virtual functions, because they allow you to properly delete objects that are created dynamically using new. Without a virtual destructor, deleting an object of a derived class through a pointer to the base class may result in undefined behavior, because the correct version of the destructor may not be called.
• Here is an example of a class with a virtual destructor:

class Base {
    public:
     virtual ~Base() {}
};
   
class Derived : public Base {
    private:
        int *p;
    public:
        Derived() {
        p = new int[10];
    }
    ~Derived() {
       delete[] p;
    }
};
   
int main() {
    Base *p = new Derived;
    delete p;
    return 0;
}

In this example, the Base class has a virtual destructor, which is declared with the virtual keyword. The Derived class is a derived class of Base, and it has its own destructor that releases the memory allocated by the p member. When the object of Derived is created in the main function, it is dynamically allocated using new, and a pointer to the base class is used to delete the object. Because the base class has a virtual destructor, the correct version of the destructor (the version in the derived class) is called, and the memory allocated by the p member is properly released. Virtual destructors are an important feature of C++, and they are used to ensure that the correct version of the destructor is called when an object of a derived class is deleted through a pointer to the base class. They are particularly useful when working with classes that have virtual functions, and they help to prevent undefined behavior when deleting dynamically allocated objects.