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Due to COVID 19 pandemic this year Direct PhD selection only consisted of an online interview.

A mail was sent by the authorities regarding the shortlist about 10 days before the interview. My interview was scheduled on 23rd of July. They had previously asked us to select 2 favourite subjects from the list of Gate topics on which they could interview upon. They had also asked for Statement of Purpose of the research work.

Subjects selected: Operating Systems and Database Systems.

On the day of interview a professor called me half an hour prior to the interview and asked me to connect as soon as they allow. There were total of 9 professors for the interview, but only 4 professors asked the questions.

Prof 1: Give a brief introduction about yourself and your academic background.

Me: Answered

Prof 2: The topic you selected for research does not match with your favourite subjects. Why so?

Me: Answered

Prof 3: What is concurrency in Operating Systems?

Me: Answered

Prof 3: Why do we need concurrency?

Me: Answered

Prof 3: Give any applications where you have found concurrency necessary?

Me: Answered

Prof 3: Which operations need concurrency

Me: Answered (with respect  to Read/Write Conflicts)

Prof 3: What is race around condition? How do we ensure it any protocol/algorithm?

Me: Explained. Specified Peterson’s Algorithm. Prof 3 told to write the code to implement Peterson algorithm

Prof 3:  Any disadvantages of Peterson Algorithm? How can we overcome it?

Me: Answered. Explained about Baker’s Algorithm

Prof 3: Ok last question You know what atomic operation mean? Can atomic operations be practically implementable?
Me: Answered (Not sure though)

Prof 4: What are transactions? What difference you notice in maintaining concurrency in OS and concurrency in Database Systems.

Me: Defined and Explained.

Prof 4: What is consistency in ACID properties. Give a formal definition.

Me: Defined.

Prof 4: I give you 2 operation Fetch and Add & Compare and Swap operations. Both are atomic.Which one will you choose for synchronization and why so?

Me: Answered.

Prof 4: Gave 2 transactions with variables X, Y and asked the difference between serial and serializable schedule. Can the given transaction be serializable. If so how and if not why?

Me: Answered

Prof 4: What protocols could you use to ensure concurrency in transactions.

Me:  Locking Protocols (2 Phase Locking)

Prof 4: 2 Phase Locking can be applied to transactions I gave before. Can you brief out the proof that 2 PL ensures serializability.

Me: Answered whatever I knew. I did not remember the proof exactly but Sir was satisfied.

Prof 1: Write a program to find number of trailing zeroes ( Expected mostly in C)


Prof 1: Your program should be written with function

Me: Modified.

Prof 1: How will you modify it if instead of n I ask you for n factorial.

Me: Told.

Prof 5: Your interests are in Cryptography. Tell me about the final year project.

Me: Answered partially. Sir wanted me to tell regarding the security parameters chosen to prove our model is secure.

Prof 5: Can you just prove formally empty set is a subset of every set.

Me: Gave an intuitive way. But was not satisfied.


Prof 1: You can leave.

The interview was nearly for an hour. The professors were expertized, kind and cooperative. The professors made the interview comfortable. It was a great interview experience from the professors of top most Institute in India.
posted Aug 9 in Interview Experience 350 views