Job interview questions and answers
We are delighted to have you here, where you will find a comprehensive collection of interview questions and answers for both C and C++ programming languages. Whether you are a fresher or an experienced professional, this page will enhance your knowledge and assist you in cracking your next interview. Best of luck!
1. What is the difference between C and C++?
C is a procedural programming language while C++ is an extension of C with object-oriented programming concepts.
2. What is a Header file in C++?
A header file contains function declarations and macro definitions to be shared between multiple source files.
3. What is the use of ‘cin’ and ‘cout’ in C++?
‘cin’ is used for accepting input from the user, and ‘cout’ is used for displaying output to the console.
4. What is a constructor in C++?
A constructor is a special member function that is used to initialize objects of a class.
5. What is the ‘new’ operator in C++?
The ‘new’ operator is used for dynamic memory allocation in C++, while ‘delete’ is used to deallocate memory.
6. What is the ‘sizeof’ operator in C++?
The ‘sizeof’ operator is used to determine the size of a variable or data type in bytes.
7. What is function overloading in C++?
Function overloading is a feature that allows a class to have multiple functions with the same name but different parameters.
8. What is the difference between pass by value and pass by reference?
Pass by value involves making a copy of the value passed to a function, while pass by reference uses a reference to the original variable.
9. What is the ‘this’ pointer in C++?
The ‘this’ pointer is a pointer that refers to the current object in a class. It is used to access the members of the class.
10. What is the difference between stack and heap memory?
Stack memory is used for local variables and function call information, while heap memory is used for dynamically allocated memory.
11. What is virtual function in C++?
A virtual function is a member function of a class that can be overridden in a derived class.
12. What is the difference between ‘malloc’ and ‘new’?
‘malloc’ is a function from the C standard library used for dynamic memory allocation, while ‘new’ is an operator in C++ for the same purpose.
13. What is a reference variable in C++?
A reference variable is an alias for an existing variable. Changes made to the reference variable affect the original variable.
14. What is the difference between ‘const’ and ‘volatile’ in C++?
‘const’ is used to declare variables as read-only, while ‘volatile’ is used to indicate that a variable’s value can be changed outside the program.
15. What is a pointer in C++?
A pointer is a variable that holds the address of another variable. It is used to achieve dynamic memory allocation and manipulation.
16. What is the ‘namespace’ feature in C++?
A namespace is used to organize code into logical groups to avoid naming conflicts. It is declared using the ‘namespace’ keyword.
17. What is the ‘static’ keyword in C++?
The ‘static’ keyword is used to declare variables and functions that are shared among all instances of a class or accessible within a single translation unit.
18. What is the difference between ‘++i’ and ‘i++’?
‘++i’ is the pre-increment operator and increments the value before it is used, while ‘i++’ is the post-increment operator and increments the value after it is used.
19. What is an abstract class in C++?
An abstract class is a class that cannot be instantiated but can have pure virtual functions. It is used as a base class for deriving other classes.
20. What is the difference between a shallow copy and a deep copy?
A shallow copy copies the values of the members of one object to another, while a deep copy creates a new object and copies the values of all members, including dynamically allocated memory.
1. What is the difference between C and C++?
Answer: C is a procedural programming language, while C++ is an extension of C with object-oriented features.
2. What is the difference between malloc() and new operator in C++?
Answer: malloc() is a function in C for dynamic memory allocation, while new is an operator in C++ for dynamic memory allocation.
3. What is a pointer?
Answer: A pointer is a variable that stores the memory address of another variable.
4. What is the difference between pass by value and pass by reference?
Answer: Pass by value involves making a copy of the value being passed, while pass by reference involves passing the memory address of the variable.
5. What is an object?
Answer: An object is an instance of a class in object-oriented programming.
6. What is the difference between private and public access specifiers?
Answer: Private members are only accessible within the class, while public members can be accessed from outside the class.
7. What is function overloading?
Answer: Function overloading is the ability to have multiple functions with the same name but different parameters.
8. What is the difference between a structure and a class?
Answer: In C++, members of a structure are by default public, while in a class, members are by default private.
9. What is the size of int in C and C++?
Answer: The size of int is system dependent, but it is typically 4 bytes in both C and C++.
10. What is the use of const keyword in C++?
Answer: The const keyword is used to define constants that cannot be modified.
11. What is virtual function?
Answer: A virtual function is a function that can be overridden in a derived class.
12. What is the difference between break and continue statements?
Answer: The break statement is used to exit a loop, while the continue statement is used to skip the rest of the loop and move to the next iteration.
13. What is the purpose of the sizeof() operator in C/C++?
Answer: The sizeof() operator is used to determine the size (in bytes) of a variable or data type.
14. What is the difference between a local variable and a global variable?
Answer: A local variable is declared within a function and has local scope, while a global variable is declared outside of any function and has global scope.
15. What is the ternary operator in C/C++?
Answer: The ternary operator (?:) is a shorthand conditional operator that evaluates an expression and returns one of two values, depending on the condition.
16. What is the difference between a constructor and a destructor?
Answer: A constructor is a special member function that is called when an object is created, while a destructor is a special member function that is called when an object is destroyed.
17. What is the difference between strcpy() and strncpy() functions?
Answer: strcpy() copies a string until it reaches a null character, while strncpy() copies a specified number of characters, even if a null character is encountered before reaching the specified length.
18. What is the use of the scope resolution operator (::) in C++?
Answer: The scope resolution operator is used to access global variables or functions from within a class or to define functions outside of a class.
19. What are the storage classes in C?
Answer: The storage classes in C are auto, register, static, and extern.
20. What is function overriding?
Answer: Function overriding is the ability to have a derived class provide a different implementation of a virtual function defined in the base class.
2. Explain the concept of Virtual Functions in C++.
Virtual functions are functions that can be overridden in derived classes. They allow the program to dynamically bind the appropriate function implementation at runtime based on the object type.
3. What is the difference between new and malloc in C++?
The ‘new’ operator in C++ is used to dynamically allocate memory for an object and calls the constructor, whereas ‘malloc’ in C is used to allocate memory without calling the constructor.
4. Explain the concept of function overloading in C++.
Function overloading allows multiple functions with the same name but different parameters. The appropriate function is called based on the number, type, and order of the arguments.
5. What is the difference between shallow copy and deep copy in C++?
Shallow copy copies the references of objects, while deep copy creates a separate copy of the objects, including their contents.
6. What is the difference between const and volatile in C++?
‘const’ is used to declare variables as read-only, while ‘volatile’ is used to indicate that a variable can be changed unexpectedly by external factors.
7. What is a lambda function in C++?
A lambda function is an anonymous function in C++ that can be defined inline and used for simple tasks without the need to declare a separate function.
8. What is a virtual destructor in C++?
A virtual destructor in C++ is used to ensure that the derived class’s destructor is called properly when deleting an object through a pointer to the base class.
9. Explain the concept of function templates in C++.
Function templates allow for generic programming by defining a generic function that can work with different data types.
10. What are the four pillars of object-oriented programming?
The four pillars of object-oriented programming are encapsulation, inheritance, polymorphism, and abstraction.
11. What is the function of the ‘sizeof’ operator in C++?
The ‘sizeof’ operator is used to determine the size of a data type or variable in bytes.
12. Explain the concept of dynamic memory allocation in C++.
Dynamic memory allocation in C++ allows for allocating memory at runtime using the ‘new’ operator and deallocating memory using the ‘delete’ operator.
13. What is a const member function in C++?
A const member function is a function that promises not to modify any member variables of the class. It is indicated by the ‘const’ keyword after the function declaration.
14. What is a namespace in C++?
A namespace in C++ is used to organize variables, functions, and classes into a named scope to avoid naming conflicts.
15. What is the difference between a class and a structure in C++?
In C++, the only difference between a class and a structure is that members of a class are private by default, while members of a structure are public.
16. What is the purpose of the ‘friend’ keyword in C++?
The ‘friend’ keyword in C++ is used to grant access to private and protected members of a class to functions or other classes that are not part of the class hierarchy.
17. What is function overloading and operator overloading?
Function overloading is the ability to have multiple functions with the same name but different parameters, while operator overloading allows using the same operator with different meanings for different data types.
18. What is the difference between a deep copy and a shallow copy?
A shallow copy creates a new object that shares the same data with the original object, while a deep copy creates a completely independent copy of the object and its data.
19. What is the use of ‘const’ keyword in C++?
The ‘const’ keyword is used to declare variables, functions, and parameters as read-only, which means they cannot be modified.
20. Explain the concept of multiple inheritance in C++.
Multiple inheritance allows a class to inherit properties and functions from multiple base classes. It can lead to conflicts when two base classes have functions with the same name, requiring manual resolution using scope resolution operators.
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