ISI Kolkata 2018 CS Interview Experience
ISI Kolkata recruits candidates on the basis of a written test and personal interview. Generally the written exam is conducted in the month of April/May followed by interview a month or so later.
Candidates are shortlisted if they clear the written cut off, or if they have a good GATE score, then they are exempted from written and given an opportunity to face the interview directly.
Written tests consist of 2 papers: MMA + PCB 
MMA is objective type maths oriented with questions coming from engineering mathematics like calculus, probability, linear algebra.
PCB is subjective consisting of core computer science concepts like data structures, algorithms. Also questions from Operating Systems, DBMS, Computer Organization & Architecture are often a regularity in their question paper set.
Once you clear the written cut off, you have roughly a months time to prepare for the interview.
In my case my interview was scheduled in the afternoon session. When I reached the campus, I had my documents verified first and then had to wait for my turn. Hardly 6-7 candidates were there for CS interview including me which came as a shock to me (may be due to multiple interview slots with multiple sessions).
Suddenly my turn came, I went there noticing 7-8 panelists were there to welcome me. One of the panelists greeted me asked me to sit down and started the conversation with whether I had Maths in 10+2 or not (:p)
P: Did you study Maths in 10+2?
Me: Yes
P: How much you scored in Maths in class X and XII?
Me: Told
P: What are you doing currently?
Me: Told I am currently working in Capgemini for the past 2 months or so.
P: What were you doing after graduating and before getting your job.
Me: Shocked! Told them my offer letter came almost 7-8 months after they interviewed me.
They were finally satisfied and moved forward to actually interviewing me the way I wanted them to.
P: How can you find GCD of two numbers; just explain roughly with the code on board with chalk.
Me: Wrote the code and explained them but I missed something and they drilled me there.
They asked me to implement the recursive code as well as the iterative one Then they switched to Algebraic Maths.
P: Given a quadratic equation, draw its graph, map the roots and give a generalized formula
Me: Done as it was fairly straight forward.
Asked me cross check questions about the quadratic equation and it continued for a while. This is where I faltered as I didn't study about it in depth.
P: You can go now!
EndGame: Rejected!
Reason: Didn’t have time to prepare for this interview as I was employed during that period. But with decent preparation, anyone can crack the interview as the level of questions is easy to moderate.