Here are 50+ common C++ interview questions and answers that will help you get through one of the toughest interviews.
1. What does Object-Oriented Programming Approach mean?
Object-oriented programming is a way to break up programs into smaller pieces. It does this by creating separate memory areas for data and functions that can be used as templates to make copies of modules on demand. OOP lets you break up a problem into a number of parts called “objects,” and then build data and functions around these objects.
2. What does a Class mean?
Using a class, all of an object’s data and code can be made user-defined data types. Objects are variables of the Class type. Once a Class has been defined, we can create many Objects of that type. A Class is a collection of Objects that are all the same type.
3. What’s hierarchical inheritance?
Hierarchical inheritance is when traits from one Class are passed on to more than one Class.
4. What are Iterators in the C++ STL?
Iterators work like Pointers and are used to get to container elements. They are used to get from one element to another. This method is known as “iterating through the container.”
5. What exactly is polymorphism?
It is the ability to show different behaviors in different situations. Operator Overloading is the process of making an Operator or a Function behave differently in different situations.
6. What’s iostream?
The iostream file is a header file in C++. It includes function prototypes for Standard Input/Output Functions, which include definitions for cout and cin. The header file is marked as #includeiostream>.
7. What’s dynamic binding?
Binding is the linking of a procedure call to the code that will be run in response to the call. Dynamic Binding is also called “Late Binding,” which means that the code for a given procedure call isn’t known until it’s called at run time.
8. What are the uses of object-oriented programming?
These are some of the places where OOP can be used:
1. Machine Intelligence Systems
2. Simulation and Modeling
3. Systems that work right now
4. Neural networks and Parallel Programing
5. Object-oriented database systems
9. What does a Destructor do?
A Destructor is used to get rid of objects that have been created by a Constructor. It is mostly used to clean up storage that is no longer needed. Destructor is a member function. Its name is the same as the class name, but a Tilde comes before it.
10. What does “Namespace” mean?
All C++ programs must include Namespaces. Namespaces in C++ give the identifiers that are used in the program a range.
11. What is the Enumerated Data Type?
An Enumerated Data Type is another User-Defined Type that lets you add numbers, making it easier to understand the program code. The enum keyword automatically enumerates a list of words by giving them the values 0,1,2,3, and so on.
12. What are Lists in C++’s STL?
The List is another very important Container in C++. It works with bidirectional, linear lists and makes it easy to delete and add items. A List can only be used one at a time.
13. List operators in C++.
new Memory allocating operator.
* Pointer to Operator endl Line feed operator :: Scope Resolution Operator::* Pointer to Member Declarator remove Memory Release Operator -> * Pointer to Operator setw Field width operator
14. Explain the catch block in C++’s Exception Handling.
A catch block is defined by the keyword catch. It catches Exceptions thrown by a throw block and then handles them as needed. The try block that throws an exception is immediately followed by the catch block that handles the exception. There can be more than one catch statement in a single program.
15. What is Functional Prototyping?
A Function Prototype shows the function’s interface to the compiler by giving details about the number and type of arguments and the type of return values. In function or method prototyping, a template is always used when declaring and defining a function.
16. What’s the ifstream() method?
The ifstream() method provides input operations. It has an open() method with a default input mode. It also gets functions such as get(), getline(), read(), seekg(), and tellg() from istream.
17. What is Multiple Inheritance?
Multiple Inheritance is the process of making a Class from a previously Derived Class.
19. What’s an inline function?
C++ has a new feature called “Inline Function” that lets small functions get rid of the cost of calls and a few other costs. An inline function is a function that is expanded in line when it is called. This helps save memory space. This is very similar to Macro Expansion.
20. What are C++ Visibility Labels?
In C++, the words Public, Protected, and Private are known as Visibility Labels. By default, the members of a Class are private. A Class with the Visibility label private is completely hidden from the outside world and serves no purpose. A Class with a Public Label is visible to the other functions and classes.
21. What are Derived Containers in the C++ STL?
What makes up a Static Data Member Variable are:
1. It is set to Zero when the first object of its Class is created.
2.It is only visible within that class, but its lifetime is the whole program.
3. Only one copy of that member is made for the whole class, and it is shared by all the objects of that class, no matter how many objects are made.
22. Make a list of the characteristics of Friend Functions.
1. It is not a member of the class for which it has been declared a Friend.
2. Since it’s not part of the class, it can’t be called using Object of that Class.
3.It can be called like a normal function, without the help of any object.
4. Usually, it uses the Objects as Arguments.
5. It can be said either in public or in the private part of a Class without changing what it means.
23. What’s a Constructor?
A Constructor is a special member function whose main job is to initialize objects of its class. The constructor is called whenever an object of the class it is associated with is created. It’s called a “constructor” because it builds the values of the class’s data members. It’s special because its name is the same as its class name.
24. What’s hybrid inheritance?
A Hybrid Class is one that is made up of more than one class. It can be made up of a parent class as well as a child class. There is no order as such. It all depends on the needs of the class.
25. What does cout and cin mean?
cout is the object of the ostream class. The cout stream is normally linked to the console output device. It is mostly used to put characters on the console screen. It’s similar to printf in C.
The object of istream class is cin. The cin stream is normally linked to the console input device. It is mainly used to get the characters from the User. It’s similar to scanf in C.
26. What’s a virtual function?
When a method is declared as a Virtual method, the C++ compiler decides which function should be used at runtime based on the type of object pointed to by the base pointer instead of the type of pointer. When the same method name is used in both the derived class and the base class, the method in the base class is marked as virtual by adding the keyword virtual before its normal declaration.
27. What does “Data Abstraction” mean?
Data abstraction is basically representing important features without caring about background details and information. Since the Classes use the idea of Data Abstraction, they are called Abstract Data Types.
STL gives you three derived containers called Queue, Stack, and Priority Queue. They are also known as Container Adapters. These can be created from different Sequence containers. All of them offer two main functions: push() and pop.
28. What do “static Data Members” mean in C++?
What makes up a Static Data Member Variable are:
1. It is set to Zero when the first object of its Class is created.
2.It is only visible within that class, but its lifetime is the whole program.
3. Only one copy of that member is made for the whole class, and all of the objects of that class share it, no matter how many objects are made.
29. Make a list of the characteristics of Friend Functions.
1. Usually, it uses the Objects as Arguments.
2. Since it is not part of the class, it can’t be called using Object of that Class.
3. It is not a member of the class to which it has been added as a Friend.
4. It can be said either in public or in the private part of a Class without changing what it means.
5. It can be called like a normal function without the help of any object.
30. What’s a Constructor?
A Constructor is a special member function or method whose job is to set up objects of its class. Its name is also the same as its class name. The constructor is called whenever an object of its associated class is made. It’s called a “constructor” because it builds the values of the class’s data members.
32. What’s hybrid inheritance?
A Hybrid Class is one that comes from more than one class. It can come from both a parent and a child class. There is no particular order. It depends on what this class needs.
33.What exactly is STL?
STL means Standard Template Library. It’s a software library for the C++ programming language that influenced many parts of the C++ Standard Library. Using STL can save a lot of time and effort, leading to programs that are of a higher quality. Namespace std is where STL components are defined.
34. What is ofstream() method?
This method provides output operations. It contains open() method with default output mode. It also inherits functions such as put(), seekp(), tellp(), and write() functions from istream.
35. What is the use of the eof() method?
If the end of the file is found while reading, the eof() method returns a value other than zero.
37. What’s the ofstream() method?
This method offers output operations. It has the open() method with the default output mode. It also uses istream’s put(), seekp(), tellp(), and write() functions.
38. What’s a Vector in STL?
A Vector is one of the most common C++ containers. It stores the elements in memory locations next to each other and lets you directly access each element using the subscript operator. A Vector can change its size on the fly, so it allocates memory as needed during runtime.
37. How can we use Virtual Functions?
We must use a pointer that is declared as a pointer to the base class to access virtual functions. Run-time polymorphism is only possible when a virtual method is called with a pointer to the base address.
38. What does encapsulation mean?
Encapsulation is the process of grouping data and functions into a single unit or block called a Class. Data Hiding is the process of keeping information from being directly accessed by a program. The data is therefore inaccessible to the outside world; only the functions inside the class can use it.
39. What’s a Stream Class?
The C++ Input/Output system is made up of a hierarchy of classes that are used to define different streams for dealing with console files and disk files. These classes are called Stream Classes and are declared in the iostream header file.
40. What’s Multiple Inheritance?
Multiple Inheritance describes a Derived Class that has more than one Base Class.
41. What is a map?
A map is a list of pairs of keys and values, where each key is linked to a single value. Values are quickly retrieved using the key. To get the associated values, we must give the key.
42. What are arguments to a command?
Arguments or parameters sent to the main() function when the program is run from the command prompt or command line. All arguments sent are strings.
43. What is a Friends Class?
By putting the keyword “friend” before the class declaration in the destination class, a class member can gain access over other class members.
44. How do I override template functions?
A Template Function can be overloaded by using template methods or regular methods of its name. This can be done as follows:
1. Call a normal method that matches exactly.
2. Call a template method that could be made with a perfect match.
3. Try normal overloading resolution to normal methods and then call the one that works.
45. Contact STL Algorithms.
Retrieve or Non-Changing Algorithms
2. Changing Programs
3. Sorting Programs
4. Set Algorithms
5. Relative Algorithms
46. Can you explain the difference between try and throw block?
Use the try keyword to start a block of statements that could cause an error. This collection of statements is called a “Try block.” Whenever an error happens, the throw statement sends it to the catch block.
47. What’s a virtual base class?
A Base Class class that is defined as Virtual in the inheritance definition. In multiple inheritance, a derived class can inherit the members of a base class in more than one way. For a virtual base class, only one copy of each of its members will be inherited, no matter how many inheritance paths connect the base class to the derived class.
48. List the Standard Template Library’s Components.
STL is made up of a number of parts, but the most important ones are:
1. Programs that do iterations
2. Algorithms
3. Containers
4.Uses
49. What does “Operator Overloading” mean?
Operator Overloading basically means making an Operator act differently in different situations. Operator Overloading is shown by the fact that the asterisk * automatically works as both a pointer and a multiplication operator. Polymorphism includes overloading of operators.
50. What is inheriting?
It is how objects of one class get the properties of objects of another class. It also allows for hierarchical classification. Inheritance is the basic idea behind Reusability.
51 . What’s RTTI?
RTTI is an acronym for Runtime Type Information. It figures out the type of any variable during execution, also called “runtime.” The RTTI Mechanism includes:
1. The operator’s name is Dynamic Cast
2. Operator Typeid
52. Include Iterators in the C++ STL.
The C++ Iterators are as follows:
1. Input
3. Unplanned
4. Output
5. In both directions
53. What is a Mutable Storage Class Specifier’s purpose?
A member variable of a constant class object can be changed by declaring it using a Specifier of a mutable storage class. It only works with non-static and non-constant member variables of the class.
54. Does the C++ programming language support both Multiple and Multilevel Inheritance?
Yes, it does support multiple inheritances and multiple levels of inheritance.
So, these are some important C++ interview questions and answers. If any of the above information is wrong or missing, please let us know by leaving a comment below.