Computer Science Basics for Beginners

💼 Common CS Interview Questions (Theory)

Whether you’re applying for internships, entry-level software roles, or freelance gigs, having a good grip on computer science theory is essential. Below are some of the most commonly asked theoretical questions in CS interviews — explained in simple terms.

📚 Core CS Topics You Must Know

• Data Structures (arrays, stacks, queues, linked lists, trees, graphs)
• Algorithms (searching, sorting, recursion, greedy, dynamic programming)
• Operating Systems (processes, memory management, scheduling)
• Databases (SQL, normalization, ACID properties, joins)
• Networks (IP, TCP vs UDP, DNS, HTTP/HTTPS)
• OOP Concepts (inheritance, polymorphism, encapsulation, abstraction)
• System Design Basics (scalability, load balancing, caching)

🧠 Most Common Interview Questions

1. What is the difference between a stack and a queue?
2. Explain the four pillars of Object-Oriented Programming.
3. What happens when you type a URL in a browser?
4. What is a deadlock in operating systems?
5. Difference between SQL and NoSQL databases?
6. What are ACID properties in databases?
7. What is the difference between processes and threads?
8. Explain HTTP vs HTTPS.
9. What is normalization in databases?
10. What is DNS and how does it work?

🔍 Example Answer – OOP Concepts

• Encapsulation: Wrapping data and code together (e.g., class with private variables).
• Abstraction: Hiding internal details (e.g., using a car without knowing how its engine works).
• Inheritance: One class inherits properties of another.
• Polymorphism: Same function behaves differently based on input (overloading/overriding).

📌 Quick SQL Cheat Sheet

SELECT * FROM users WHERE age > 18;
INSERT INTO jobs (title, company) VALUES ('Software Engineer', 'UdaanPath');
UPDATE users SET name='Amit' WHERE id=5;
DELETE FROM jobs WHERE id=10;
  

📝 Tips to Prepare

• Revise core topics from each subject (OS, DBMS, Networks, OOP, DSA)
• Practice explaining concepts in your own words
• Use real-world analogies — e.g., “stack is like a pile of plates”
• Prepare 2–3 solid project descriptions (like building a blog, portfolio site, etc.)
• Mock interviews help a lot! Try platforms like Pramp, InterviewBit, or friends.

📌 Bonus: Common HR Questions

• Tell me about yourself.
• Why do you want to join this company?
• Where do you see yourself in 5 years?
• Tell me about a challenging situation you handled.

✅ Coming Next

In the next chapter, we’ll help you build an impressive tech resume — with real-world examples and formatting tips.