a/c tech Interview Questions and Answers

1. What is the difference between C and C++?

   • Answer: C is a procedural programming language, while C++ is an object-oriented programming language. C++ extends C by adding features like classes, objects, inheritance, polymorphism, and more. C primarily relies on functions, while C++ emphasizes data encapsulation and code reusability.

2. Explain the concept of pointers in C++.

   • Answer: Pointers are variables that store the memory address of another variable. They are declared using the asterisk (*) symbol. Pointers allow direct memory manipulation, enabling dynamic memory allocation and efficient data structures. Understanding pointers is crucial for working with arrays, linked lists, and other advanced C++ concepts. They also allow for passing arguments by reference, improving efficiency.

3. What is the difference between `malloc()` and `new`?

   • Answer: `malloc()` is a C function that allocates a block of memory of a specified size. It returns a void pointer, requiring explicit casting to the desired data type. `new` is a C++ operator that allocates memory and constructs an object of a specified type. It automatically calls the constructor of the object and handles potential exceptions. `new` is generally preferred in C++ for its type safety and automatic object construction/destruction.

4. Explain the concept of inheritance in C++.

   • Answer: Inheritance is a mechanism where a class (derived class or child class) acquires the properties (data members) and functionalities (member functions) of another class (base class or parent class). It promotes code reusability and establishes an "is-a" relationship between classes. Different types of inheritance exist, including single, multiple, multilevel, and hierarchical inheritance.

5. What are virtual functions and polymorphism?

   • Answer: Virtual functions are member functions declared using the `virtual` keyword in the base class. They allow for runtime polymorphism, where the correct function to call is determined at runtime based on the object's type. Polymorphism enables using a base class pointer to refer to derived class objects, calling the appropriate version of the virtual function based on the actual object type. This is crucial for flexible and extensible designs.

6. What is a constructor and destructor in C++?

   • Answer: A constructor is a special member function with the same name as the class. It is automatically called when an object of the class is created. It is used to initialize the object's data members. A destructor is also a special member function with a tilde (~) before the class name. It is automatically called when an object is destroyed, allowing for resource cleanup (like deallocating memory).

7. Explain the difference between `#include ` and `#include "myheader.h"`.

   • Answer: `#include ` searches for the iostream header file in the standard system include directories. `#include "myheader.h"` searches for the myheader.h file first in the directory containing the current source file and then in the standard include directories. The angle brackets indicate a standard library header, while the double quotes indicate a user-defined header file.

8. What is the purpose of a header file (.h or .hpp)?

   • Answer: Header files contain declarations of functions, classes, and variables. They don't contain the actual function definitions (except for inline functions). They allow you to separate interface from implementation, promoting modularity and code reusability. The compiler uses header files to ensure type consistency and linkage between different source files.

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