54 Must-Know Computer Science Interview Questions & Answers [For Freshers & Experienced]

A career in computer science, though full of opportunities can be quite challenging. There is a lot of competition, and recruiters are always looking for applicants with a deep understanding of the subject. 

Did you know that computer science professionals in India have an impressive 78% employability rate? It’s no wonder this field is highly sought after! But landing a job in computer science takes more than just skills and education—you need the ability to ace interviews by applying your knowledge and showcasing smart problem-solving.

Cracking a computer science interview requires a solid understanding of fundamental concepts like programming languages, algorithms, and data structures. Beyond technical skills, you also need the ability to apply them practically to demonstrate you’re job-ready. 

An efficient way to prepare for a computer science interview is to create computer science interview questions and answers. Randomly looking up questions might not prove very useful. What you need is a structured outline to help ace your interview.

Read along to explore the top 50 computer science interview questions!

Enroll in upGrad’s Online Software Development Courses and get ready to land your dream job.

Top Computer Science Interview Questions & Answers

In computer science interviews, you are evaluated on a range of criteria, from your technical skills and problem-solving abilities to your understanding of algorithms and specialized subjects like AI and machine learning. Successful candidates show both theoretical understanding and practical application. 

We shall further explore computer science interview questions, providing insights to help you prepare effectively and confidently: 

Also Read: Top latest technologies in computer science

Basic Computer Science Interview Questions

Basic-level computer science interview questions and answers cover the essential concepts, including problem-solving techniques, basic programming, and foundational algorithms.

Following are some beginner-level computer science interview questions and answers focusing on basics:

1) What is a Computer System?

Ans: A computer system is a combination of CPU, memory, and Operating System and supplementary devices connected to it like keyboard, mouse, speakers, etc. In other words, a computer system is an integrated set of hardware, software, and data that collectively perform computational tasks. It consists of input devices ( like keyboard, and mouse), output devices ( like monitor, and speaker), processing units (CPU), and storage devices ( like hard disk).

2) What is an array?

Ans: An array is a data structure that stores a collection of elements of the same data type in a contiguous block of memory. It allows efficient access and manipulation of data using indices, with each element stored at a specific position, making it easy to manage large sets of data.

3)  What do you mean by a Microprocessor?

Ans: A microprocessor refers to an integrated circuit functioning as the central processing unit of a computer system. It is the central processing unit (CPU) of a computer on a single integrated circuit. It performs logic,  arithmetic, control, and input/output operations needed for computing.

Example: Intel Core i9 is a widely used microprocessor.

4) What is meant by debugging?

Ans: Debugging can be explained as the process of finding, evaluating, and correcting software problems popularly known as software bugs.

5) What is an IP address?

Ans: An IP (Internet Protocol) address is a unique identifier assigned to every device connected to a network. It enables devices to communicate over the internet. There are 2 types, namely IPv4 (32-bit) and IPv6 (128-bit). IPv6 allows the use of more devices.

6) What are the components of a Computer System? 

Ans: A computer system consists of the following components:

• Memory (primary and secondary).
• Central Processing Unit (CPU) containing the control unit and the arithmetic-logical unit.
• Input and output devices such as a mouse, keyboard, printer, speakers, and more. 

7)  What are the most popular Operating Systems?

Ans: Operating systems act as an interface between hardware and software resources. Some popular Operating Systems are Microsoft Windows, Linux,  Android and OSX are some of the most popular operating systems.  

8) What do you mean by SDLC?

Ans: SDLC stands for Software Development Life Cycle. It is the process of creating, planning, deploying, and testing a system. It focuses on producing a software product The SDLC involves stages like requirement analysis, design, coding, testing, deployment, and maintenance

9)  What are some popular computer processors?

Ans: Intel Core i9, Intel Core i7, Intel Core i5, AMD Ryzen 5, and AMD Ryzen 7 are some of the most popular computer processors. The AMD Ryzen 9 processor is another popular computer processor known for its high performance in video editing and gaming. 

10) What is a framework?

Ans: A framework is a reusable set of libraries and tools that provides a structured method to develop software applications. It is a platform that allows you to create software applications, giving you the foundation on which you can create a program for a particular platform. It might consist of predetermined functions and classes. You can use a framework to manage the hardware, and inputs, and work with the system software. 

Example: React is a JavaScript framework used for designing user interfaces in web development.

11) What is a binary search?

Ans: Binary search is an efficient algorithm to locate a target value within a sorted array. It operates by repeatedly dividing the search interval in half.

12) What is a memory leak?

Ans: A memory leak occurs when a program allocates memory but fails to release it, causing the program to consume more memory over time.

13) What do you mean by DHCP?

Ans: DHCP stands for Dynamic Host Configuration Protocol, which is used for providing a quick, automatic, and centrally managed distribution of IP addresses within a network. DHCP is often used for configuring subnet mask, default gateway, or DNS server information.

14) What is a loop in programming?

Ans: A loop is a control structure in programming that repeats a block of code multiple times. It is used when you want to execute the same code repeatedly, based on certain conditions. The most common types of loops are the for loop, while loop, and do-while loop. Loops are essential for tasks like processing lists of data, performing calculations, or repeatedly checking conditions until a certain state is reached.

15) What is a relational database?

Ans: A relational database is a type of database that stores data in tables with rows and columns. Relationships between data are established through primary and foreign keys. Examples of relational databases are MySQL, PostgreSQL, and Oracle, typically accessed using SQL.

16) Why is grouping used in CSS3?

Ans: The use of grouping in CSS3 allows users to reuse and apply the same CSS styles to multiple HTML entities, making the code more efficient and maintainable. By grouping selectors in one declaration statement, you can reuse styles across different elements, reducing redundancy and minimizing code. This promotes cleaner, more organized code, improving both performance and readability.

17) What is a File, and why is it essential?

Ans: A file is a location that stores data and information. It is always located inside a storage device by using the name assigned to it. It keeps the information either permanently or until you delete it. They are a fundamental component of computer science. 

Example: A .jpg file is used to store images on a computer.

Also Read: Major Projects for Computer Science Students

Intermediate Computer Science Interview Questions

The intermediate-level computer science interview questions will focus on key topics like programming languages, algorithms, and data structures. Here are the computer science interview questions and answers for the intermediate level. Let’s discuss on to intermediate-level computer science interview question topics:

Also Read: Top 20 Programming Languages of the Future

18) What do you mean by a Class and a Superclass? 

Ans: A class is a template for creating objects in object-oriented programming. A Class defines the features of an object like how it will respond to a message and what kind of a message the object will react to. A superclass is the basis of the class we consider. It is the parent class from which, other subclasses inherit.

Example: In C++, a Vehicle class can be a superclass for Car and Bike subclasses

19) Explain Dijkstra’s algorithm.

Ans: Dijkstra’s algorithm finds the shortest path between a source node and all other nodes in a weighted graph. The Dijkstra’s algorithm calculates the shortest path from a source node to all other nodes in a weighted graph. It repeatedly selects the node with the smallest tentative distance, updates the distances of its neighbors, and continues until the shortest paths to all nodes are found.

20) What is the difference between multitasking and multiprocessing?

Ans: In multitasking, a processor performs several programs at once by switching between them. This process does not require multiple processors. Whereas in multiprocessing, a processor performs numerous functions and programs simultaneously with the help of several processors.

21) Explain the concept of polymorphism in object-oriented programming.

Ans: Polymorphism allows objects of different classes to be treated as objects of a common superclass. It enables the use of the same method name to perform different tasks. 

Read More Here: Polymorphism In OOPS: What is Polymorphism [Detailed Explanation]

22)  What is Inheritance in Computer Science? 

Ans: Inheritance is a component in programming that we use frequently in computer science professions. It refers to the property that gets passed from a superclass to a subclass. It is a concept in object-oriented programming where one class (subclass) inherits properties and methods from another class (superclass).

Example: In Python, a Car class can inherit from a vehicle class, reusing attributes like fuel type while adding specific traits like a model.

23) What's the difference between TCP and UDP?

Ans: TCP (Transmission Control Protocol) is a connection-oriented protocol that provides reliable data transmission through error-checking, flow management, and acknowledgment whereas UDP (User Datagram Protocol) is connectionless, quicker, and ideal for applications that prioritize speed over dependability, such as video streaming or online gaming.

Here are the key differences between TCP and UDP protocols:

23) What do you mean by a Chipset and what role does it play in a computer?

Ans: A chipset consists of electronic components that manage data flow between the CPU, memory, and other components. It determines system compatibility and performance. It helps you control the communication between different devices and is crucial for determining whether a computer system is functioning properly or not. It controls the communication between all the computer components such as the CPU, the storage, and the RAM.

Moreover, It tells you which and how many USB devices your motherboard can support. Primarily, chipsets help a computer system in controlling peripheral components such as the keyboard, monitor, mouse, or printer. 

Example: The Intel Z690 chipset is used in gaming PCs.

24) What is the difference between navigational and relational databases?

Navigational databases access data by defying the path to find the needed data. On the other hand, in relational databases, one can access data by stating exactly what one wants. Unlike navigational databases, relational databases do not have hierarchical or network structures.

Let’s take a look at the major differences between navigational and relational databases:

Also Read: Career in Software Development: 13 Various Job Roles To Choose From

25) What is the time complexity of binary search?

Ans: The time complexity of binary search is O(log n), where n is the number of elements in a sorted array. Binary search works by repeatedly dividing the search space in half, making it much faster than linear search, which has a time complexity of O(n).

26) What are the benefits of using a linked list over an array?

Ans: Linked lists provide various advantages over arrays, including dynamic memory allocation, efficient insertion and deletion particularly at the beginning or middle and not having to resize. However, they have additional memory overhead due to pointers.

27) How do you differentiate between a Method and a Constructor?

Ans: Here’s the difference between a method and a constructor.

Also Read: Constructors in Python [Guide] 

28) What is dynamic programming?

Ans: Dynamic programming is an optimization technique used to solve problems by breaking them down into simpler subproblems. It stores the results of already solved subproblems to avoid redundant calculations, thus improving efficiency. It is commonly used in problems like the Fibonacci sequence, shortest path, and knapsack.

29) Explain what a "hash collision" is in a hash table.

Ans: A hash collision occurs when two different keys produce the same hash value in a hash table. This can be resolved by techniques such as chaining (linking elements at the same index) or open addressing (finding an alternative location for the colliding element).

30)What are the differences between stack and heap memory?

Ans: Stack memory is used for static memory allocation, such as local variables and function calls, with a fast allocation/deallocation process. Heap memory is used for dynamic memory allocation, allowing objects to be created during runtime, though it has slower access and requires manual memory management.

31)Explain the difference between method overloading and method overriding.

Ans: Method overloading occurs when multiple methods with the same name exist in a class, but with different parameters. It is resolved at compile time. Method overriding happens when a subclass provides a specific implementation of a method already defined in its superclass. It is resolved at runtime.

32) Explain the concept of pass-by-reference and pass-by-value.

Ans: In pass-by-value, a copy of the variable’s value is passed to the function, so changes made within the function do not affect the original value. In pass-by-reference, a reference to the actual variable is passed, so changes made in the function directly modify the original variable.

33)  What is Cryptography? What is the use of Cryptography?

Ans:  Cryptography, also known as cryptology, is the study and practice of techniques for secure communication. It focuses on studying techniques that prevent unwanted parties from accessing your information or communication which in turn leads to ensuring confidentiality, integrity, and authenticity. 

The main purpose of cryptography is to convert information into an unreadable format, to ensure confidentiality, integrity, and authenticity. Techniques like data encryption are used for this purpose.

Example: AES (Advanced Encryption Standard) is a cryptographic algorithm used for securing sensitive data.

Also Read: Cryptography in Cybersecurity: Definition, Types & Examples

34)  What do you mean by an Algorithm?

Ans:  An algorithm refers to a definite sequence of executable and well-defined instructions for solving a class of problems or performing a computation. It is a step-by-step set of rules for solving a problem or performing a task. It is independent of language and instead focuses on logic and efficiency.

Example: QuickSort is an algorithm that arranges a list of objects in ascending or descending order.

Also check: Learn Java Free!

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Advanced Computer Science Interview Questions

Advanced-level computer science interview questions will cover topics such as complex algorithms, system design, and handling large-scale applications. They are designed for individuals with advanced knowledge in computer science.

Below are some computer science interview questions and answers for expert professionals:

35) Explain the concept of "race conditions" in concurrent programming. How can it be prevented?

Ans: A race condition occurs when two or more threads access shared resources simultaneously, leading to unpredictable outcomes. To prevent race conditions, synchronization techniques like mutexes, semaphores, or locks are used to ensure that only one thread can access the resource at a time, maintaining consistency and avoiding conflicts.

36)  What is the role of a distributed hash table (DHT) in a distributed system?

Ans: A Distributed Hash Table (DHT) is a decentralized distributed system that provides a key-value mapping where each node is responsible for a portion of the hash table. DHTs are commonly used for distributed file systems and peer-to-peer networks like BitTorrent. They ensure efficient and scalable lookup of data without relying on a central server, and they can self-organize in the face of node failures or joins.

37) What is the concept of event-driven programming? How is it used in GUI?

Ans: Event-driven programming is a paradigm where the flow of the program is determined by events, such as user interactions, sensor outputs, or messages from other programs. In GUI development, events like button clicks, mouse movements, or key presses trigger actions (like function calls). In web development, it is used in JavaScript to handle user input, enabling dynamic and interactive web applications.

38) What is the Main Difference Between Thread and Process?

Ans: Thread is a section of a process whereas a Process is a program within the execution. A process can’t have multiple threads but vice versa isn’t possible. 

Refer to the table below to know the difference between a thread and a process.

39) What is Primary Memory?

Ans: Primary memory is the central memory of a computer which you can access by using the Central Processing Unit (CPU). It contains information temporarily until the particular process completes its execution. 

40) What is the Difference Between the Interpreter and Compiler?

Ans: There are plenty of differences between a compiler and an interpreter. First, there’s the difference in speed. Interpreted code runs slower than compiled code. The interpreter doesn’t produce an output program so you must evaluate the source while executing the code, whereas the compiler produces an output program as an exe file which you can run separately from the source.

The interpreter remains in the memory during interpretation. On the other hand, the compiler executes the target program separately and doesn’t have to remain in the memory for this process. Finally, the interpreter would show all the errors one by one while the compiler would show them all at once after completing the compilation. 

Know More Here: Difference between an interpreter and a compiler.

41) What are the various types of access modifiers?

Ans: Access modifiers are used to determine the visibility and accessibility of classes, methods, and variables. There are four kinds of access modifiers: Private, Public, Protected, and Default. The private modifier makes the class (or method) visible to a specific class while the public modifier makes it visible to everything. The protected modifier would make it visible to particular packages. 

Here’s a further look at the different types of access modifiers:

• Public: Accessible from anywhere (e.g., public int age;).
• Private: Accessible only within the class (e.g., private String name;).
• Protected: Accessible within the same package and by subclasses (e.g., protected void display();).
• Default (Package-Private): Accessible only within the same package (e.g., int count;).

42) What is the difference between a B-tree and a B+ tree?

Ans: A B-tree is a balanced tree where each node can contain multiple keys, allowing for efficient searching, insertion, and deletion. It can store both keys and values in internal nodes In a B+ tree, all actual data values are stored in the leaf nodes, while internal nodes only store keys to direct the search process. 

This structure allows for more efficient range queries in B+ trees since all values are in leaf nodes, which are linked for quick traversal. B+ trees are commonly used in databases and file systems for better performance in large-scale data storage.

43) What is a bloom filter?

Ans: A Bloom filter is a probabilistic data structure used to test whether an element is a member of a set. It works by mapping elements to a fixed-size bit array using multiple hash functions and allows for fast membership checks with a small memory footprint but can result in false positives. 

Bloom filters are widely used in databases, network systems, and distributed systems like Google's Big Table. Bloom filters are commonly used in scenarios like web indexing, databases, and distributed systems (eg, Google’s BigTable) where fast, efficient checks for data membership are essential, and occasional false positives are acceptable.

44)How would you implement a fraud detection system for credit card transactions?

Ans: A fraud detection system for credit card transactions can be built by using the following procedure: 

• Collecting transaction data such as user demographics, transaction amount, time, merchant details, and location
• Extracting features to identify fraudulent activity
• Training a machine learning model to predict the likelihood of fraud.
• Implement real-time monitoring using stream processing frameworks
• Detecting outliers in the data.
• Triggering an alert on fraud detection or taking immediate action, such as temporarily blocking the transaction 

45) How would you design a chat application with support for multimedia messages and real-time communication?

Ans: The following methods can be used to design a chat application:

• Using WebSockets to establish a persistent connection between clients and the server for real-time message delivery.
• Implementing file upload capabilities can store media distributed file system
• Using a message broker to ensure reliable message delivery and persistence
• Using push notifications for when users are offline, using services like Firebase Cloud Messaging Encrypting messages using end-to-end encryption to ensure privacy.

46) Explain the CAP theorem.

Ans: The CAP theorem states that in a distributed system, it is impossible to simultaneously guarantee all three. A system can guarantee at most two of the following three properties.

• Consistency: All nodes have the same data at any given time
• Availability: Each request receives a response
• Partition tolerance: The system continues to function despite network partitions

47) What is a deadlock, and how can it be avoided in an operating system?

Ans: A deadlock is a condition where two or more processes are blocked forever, each waiting for resources held by the other. It is a situation in a multi-process environment where two or more processes are waiting for resources held by each other. This prevents further progress and causes the system to halt.

Example: Consider a situation where there are two threads (Thread A and Thread B) and two resources (Resource 1 and Resource 2). 

Thread A locks Resource 1 and waits for Resource 2 to complete its task. At the same time, Thread B locks Resource 2 and waits for Resource 1 to complete its task. This creates a deadlock.

A deadlock can be avoided by ensuring that at least one of the following conditions is not met:

• Ensuring that at least one resource is available to avoid blocking
• Preventing processes from holding one resource while waiting for others
• Allowing resources to be preempted from a process if necessary
• Avoiding circular dependencies by defining a linear ordering of resources.

48)What is the difference between "deep copy" and "shallow copy" in C++?

Ans: In C++, a shallow copy creates a new object and only copies the pointers. On the other hand, a deep copy creates a completely independent object, copying both the object and any dynamically allocated memory, ensuring no shared references between the original and the copy.

49)Explain the concept of MapReduce and its applications.

Ans: MapReduce is a programming model used for processing large datasets in parallel across distributed systems. It is used in big data processing for tasks such as log analysis, data mining, and indexing.

It consists of two phases:

• Dividing the task into smaller chunks and processing them independently
• Aggregating the results from the map phase into a final output

50) What is the difference between a monolithic architecture and a microservices architecture?

Ans: In a monolithic architecture, the entire application is built as a single, tightly coupled unit where all components are interdependent. In contrast, a microservices architecture breaks down the application into small, independent services, each responsible for a specific business function. Microservices enable greater flexibility, scalability, and fault isolation but introduce challenges in managing distributed systems, inter-service communication, and data consistency.

51) What is the role of a Database Management System (DBMS) in software development?

Ans: A Database Management System (DBMS) is used to manage data storage, retrieval, and manipulation efficiently. Here is the role of a database management system:

• Organizes data using schemas, tables, or indexes.
• Enforces constraints on data to maintain accuracy.
• Handles multiple users accessing data simultaneously.
• Ensures safety of data safety during failures.
• Provides high-level query languages (e.g., SQL).

Ans: A thread and a process are both fundamental units of execution in an operating 

52)  How does Machine Learning integrate with software development?

Ans: Machine learning improves the software development process by automating complex tasks and enhancing user experience. Integration is carried out through frameworks like TensorFlow or libraries like scikit-learn.

Example: E-commerce applications like Amazon use machine learning algorithms to suggest products based on user behavior.

53) What are the different types of Data Structures, and where are they used?

Ans: Data structures organize and store data efficiently for effective manipulation and retrieval. Different types of data structures are used based on specific algorithmic and application needs. Following are the different types of data structures along with their use and example:

54) Explain the process of normalization in database design.

Ans: Normalization in database design is the process of organizing data to reduce redundancy and improve data integrity. The goal is to ensure that the database is efficient, flexible, and free from anomalies. This process involves dividing large tables into smaller, related tables and ensuring that relationships between the data are logically structured.

1. 1NF (First Normal Form): Ensures that each column contains only atomic (indivisible) values, eliminating duplicate columns and multi-valued attributes.
2. 2NF (Second Normal Form): Removes partial dependencies, meaning that every non-key attribute is fully dependent on the primary key, eliminating redundancy that comes from partial key relationships.
3. 3NF (Third Normal Form): Removes transitive dependencies, meaning that non-key attributes should not depend on other non-key attributes, ensuring that every non-key attribute is directly related to the primary key.

Example: In a database, storing customer information in a separate table from orders ensures that if customer details change, the changes don’t affect the order data. 

Also Read: Best Computer Programming courses for job

Useful Computer Science Interview Tips

Any interview preparation process can be nerve-wracking if you do not follow what you need to know. Avoid any such feeling by following a structured preparation plan that helps you confidently present your learning and abilities. Below are a few tips to assist you in acing your interview:

• Thoroughly research your role and organization: You should be very informed about the position and company. Then, you can accordingly correlate how you are a good fit there. With prior knowledge, you can show interest in the company and position by posing questions that indicate your research.
• Understand the Job Requirements: Before attending the interview, read the job description to identify the core technologies and skills required. For example, if the job requires Django, focus on preparing for web development questions.
• Keep Core Subject Knowlege at Fingertips: Make sure you revise computer science fundamentals like algorithms, data structures, operating systems, and databases. For example, be ready to write SQL queries to fetch data using joins.
• Strengthen Problem-Solving Skills: Practice coding problems on platforms like HackerRank. You should overall focus on brushing up your soft skills along with honing your technical skills.

Learn how to demonstrate your problem-solving skills in interviews. Join the free course on Complete Guide to Problem Solving Skills.

• Prepare Behavioral Responses: Be ready to answer questions related to teamwork, leadership, or conflict resolution. For example, you can answer how you worked with your team members to solve a bug in a short duration of time. Be prepared for situation-based questions that assess your emotional intelligence.
• Keep Up with Trends: Be updated with the latest trends in computer science, such as artificial intelligence and cyber security. For example, learn how to use TensorFlow for data analytics.
• Practice Interview: Take mock interviews with the help of peers and online platforms to gain confidence. For example, conduct a virtual mock interview using AI to simulate the conditions.

Conclusion

Computer science is a lucrative career industry in India as well as worldwide. Being a computer professional opens the doorway to various advanced and emerging domains such as data science, AI, and ML. Hence, its scope is quite large in terms of job opportunities.

Computer science interviews test your ability and eligibility to fit into an organizational role. You need to clear a set of tests and passing criteria to successfully clear the interview. Doing so requires a dedicated preparation strategy, from knowing your content and field to mastering your ability to effectively answer those questions. Thus, you need to invest time and hard work to be able to be successful in computer-related interview questions.

Preparing for a career in computer science can prove highly lucrative if you advance your current skill set with courses such as upGrad’s Artificial Intelligence courses.

Also, check out our online Software Development Courses from the World’s top Universities to fast-track your career!

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Reference Links:
https://www.entrepreneur.com/en-in/growth-strategies/indian-graduates-employability-rate-reaches-5481-per/484203
https://www.geeksforgeeks.org/most-asked-computer-science-subjects-interview-questions-in-amazon-microsoft-flipkart/
https://www.interviewbit.com/computer-science-interview-questions/ 
https://www.naukri.com/code360/library/computer-science-interview-questions