Technical interviews in campus placements test four to six core subjects depending on the company. This guide covers the most asked questions in each, with the type of answer that actually impresses interviewers.
Object-Oriented Programming
Must-know: the four pillars (encapsulation, inheritance, polymorphism, abstraction) with real-world examples, not textbook definitions. Common questions: “What is the difference between overloading and overriding?”, “What is a virtual function?”, “What is multiple inheritance and why does Java not support it?”, “Explain the difference between a class and an object.” For each answer, give a one-sentence definition and then a one-line code example.
Data Structures and Algorithms
Every technical interview asks at least one DSA question. Prepare: arrays, linked lists (reverse a linked list is still asked in 2025), stacks, queues, trees (inorder/preorder/postorder traversal), and basic graphs. Time and space complexity for sort algorithms is asked more often than the code itself. Know Big-O for bubble, merge, quick, and binary search by heart.
Database Management Systems
Top DBMS questions: normalization (1NF to 3NF with examples), ACID properties (with what happens when each is violated), difference between DELETE/TRUNCATE/DROP, what an index does and when not to use one, and basic JOIN types with an example query. If you can write a working GROUP BY query with HAVING, you are ahead of 70% of candidates.
Operating Systems
Expected topics: process vs thread (and when to use each), deadlock (four conditions and how to prevent), CPU scheduling algorithms (FCFS, SJF, Round Robin — know their trade-offs), virtual memory and paging, and the difference between mutex and semaphore. OS questions are more conceptual than code-based — precision of definition matters.
Computer Networks
Know the OSI model layers (and what happens at each), TCP vs UDP trade-offs, what DNS does step by step, the three-way handshake, and the difference between HTTP and HTTPS. For companies that build web or cloud products, these come up in almost every first interview round.
How to Prepare in the Last 72 Hours Before an Interview
Do not study new topics. Revise your notes, especially definitions and complexity values. Sleep adequately — memory consolidation during sleep directly affects recall speed. On the day, if you do not know an answer, say “I am not certain of the exact answer but my understanding is X — is that on the right track?” Interviewers consistently prefer honest uncertainty over confidently wrong answers.