C++ Interview Questions for Beginners: Most Asked Topics – Part 1

In this blog post, I will discuss some of the most frequently asked C++ interview questions for beginners. I will cover data types in C++, provide a detailed guide on classes and structures in C++ with examples, address interview questions related to C++ pointers, and finally, explain the const keyword and reference types in C++. Although there are many questions typically asked in interviews, I will present them in parts so that you can learn step by step. Stay with us and ace your next C++ interview.

If you’re preparing for a C++ interview as a beginner, understanding the core concepts of the language is crucial. C++ is a powerful language that builds on the foundation of C, introducing object-oriented features and more. In this article, we’ll explore some fundamental C++ interview questions that will help you grasp the basics and demonstrate your understanding during an interview.

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Data Types Related C++ Interview Questions

In a C++ interview, the interviewer might ask you to share your brief knowledge about data types in C++, so it is crucial to understand the basic data types. Data types in C++ are the building blocks of data manipulation; in other words, we have certain keywords to write code in C++. Below, I have shared the most common data types that are often part of C++ interview questions and that you should be familiar with.

Understanding these basic data types is essential, as they form the basis for variables and data manipulation in C++. in the next section I am going to cover struct and class related cpp interview questions.

Explain the difference between struct and class.

If you are preparing for a C++ interview and are not familiar with struct and class, I highly recommend pausing your preparation for other C++ interview questions and focusing on these concepts, as they are the heart of C++. The interviewer will almost certainly ask about them.

Both struct and class are used to define custom data types, but they have a key difference in terms of access control:

Struct: Members of a struct are public by default. This means that the data and functions defined within a struct can be accessed directly without any restrictions, unless specified otherwise. please check below example of struct keyword.

struct Point {
    int x;
    int y;
};

Class: Members of a class are private by default. This means that they are only accessible from within the class itself, unless otherwise specified with access specifiers like public, protected, or private. please check below example of class keyword.

class Circle {
private:
    double radius;

public:
    void setRadius(double r) { radius = r; }
    double getRadius() { return radius; }
};

The choice between struct and class depends on the level of encapsulation and access control you require for your data structures.

What is a pointer in C++?

Nowadays, if you are not familiar with pointers and function pointers, there is a high chance the interviewer could reject you. Therefore, while preparing for a C++ interview, it is crucial to gain experience with pointers in general. Below, you will find all the necessary knowledge about pointers for a C++ interview.

A pointer is a powerful feature in C++ that allows you to directly manipulate memory addresses. It is a variable that stores the address of another variable.

In other words, pointers allow you to directly access the memory of your variables and functions. Why is this important? Because C++ gives you the flexibility to work with direct memory access, enabling you to write optimised code with minimal memory consumption

Here are some common uses for pointers:

• Dynamic Memory Allocation: Pointers enable the allocation and deallocation of memory at runtime using operators like new and delete.
• Function Arguments: Pointers can be used to pass functions and arrays to other functions, allowing for efficient data manipulation without copying large amounts of data.
• Resource Access: Pointers provide a way to access and manipulate resources efficiently, which is especially useful in systems programming.

int main() {
    int value = 42;
    int* ptr = &value; // ptr holds the address of value
    std::cout << "Value: " << *ptr << std::endl; // Dereferencing ptr gives the value
    return 0;
}

Understanding pointers is crucial for working with memory management and resource allocation in C++.

How does the const keyword work in C++?

The const keyword is used to declare variables whose values cannot be changed after they are initialized. This feature helps enforce immutability and prevent accidental modification of data. Here are some common uses of const:

Constant Variables: Declaring variables as const ensures their values remain unchanged.

const int MAX_USERS = 100;

Function Parameters: Using const with function parameters prevents modification of the arguments passed to the function.

void printValue(const int value) {
    std::cout << value << std::endl;
}

Return Types: Functions can also return const values to prevent modifications to the returned data.

The const keyword enhances code safety by ensuring certain values remain constant throughout the program.

What is a reference in C++?

A reference is an alias for another variable, providing an alternative name for that variable. Once a reference is initialized, it cannot be changed to refer to another variable. References are often used for passing arguments to functions to avoid copying large objects and enhance performance.

Example of reference usage:

void increment(int& value) {
    value++;
}

int main() {
    int number = 10;
    increment(number); // number is passed by reference
    std::cout << "Number: " << number << std::endl; // Output: Number: 11
    return 0;
}

References provide a way to access and modify variables without copying their values, making them efficient for large data structures and objects.

Summarizing C++ Interview Questions Part-1

Understanding these basic C++ concepts is essential for beginners preparing for interviews. By mastering data types, structures, pointers, the const keyword, and references, you can demonstrate a solid foundation in C++ programming. As you delve deeper into C++, you’ll find these concepts invaluable for writing efficient and effective code.

Good luck with your interview preparation, and keep practicing to sharpen your C++ skills!