“Structured, conceptual and practical test of subjects.”

Hi,

I am one of the eight fortunate ones who were selected for OCES Computer Science program last year. I am Abhilash Bhardwaj, currently working as Trainee Scientific Officer in BARC, Mumbai. Last year I was shortlisted for interview based on my performance in BARC TS Online Exam ( 170/300 while cut-off was 159) . Approximately 100 students were called last year for interview, out of that, 8 students were finally selected for this program ( 765/1000 Interview Score where Interview cut-off was 650).

So now coming to interview experience.

My interview was scheduled on 11th June last year. I reported in the morning. After basic document formalities I went to the waiting room. I was second in sequence so nearly after one hour my name was called by the panel. We all have fear of interview especially when you know this is going to last for an hour or so. I entered into the interview room. A total 6 people were there in the room. They started with the basic introduction about my college, my cgpa ( they asked how you managed in college ), my native place etc, just to make me comfortable with the panel.

And here it begins !!!!!

The first question was by the President regarding the subjects that interests me more.They did not ask me to list it down but I jotted it down on a paper. I wrote Operating System, RDBMS, COA , DS and C. Just when I finished,the panel asked that why you have written COA, as most of people don’t write this. ( Don’t answer like its my favourite subject and all, you need to justify it ). I answered the relevance of advancement of architecture, processor design, multiprocessor systems, GPUs in current era. I gave examples of Blockchain and Machine learning where we require high computing power. Then, as I mentioned, I used the term GPU so they began with that… ( so the moral of the story-don’t use just fancy terms if don’t know it!!). Fortunately I was aware of basics of GPU. They asked whether is SIMD,MISD,MIMD or SISD, why we are using this,how it makes computation faster,can’t we achieve the same with CPU, power requirements of CPU and GPU etc. I was knowing the plot not the entire story so at last I surrendered on a comparative question of CPU and GPU, I accepted my defeat. They responded don’t worry it was out of context because of your interest in GPU we asked this much. Then they asked basics of RISC, CISC,current RISC architectures, difference of RISC and CISC, Microprogramming and its types ,Pipelining hazards, how we avoid them, Linking and Loading operations,Addressing modes, CPU flag register etc.

Here my suggestion is to speak relevant to the topic but take examples, explain on paper sheets, draw diagrams. Like when you are explaining Microprogramming start with why we need this, then its categorization, difference etc. They will ask question in every step of explanation. You need to know why RISC, What is RISC and How it is implemented. These concepts are not beyond our understanding. If you don’t know the answer better to say sorry!

Then they switched to Operating system. They started with what was taught in B.Tech. Then they asked me write a critical section program where I was needed to produce H2OH2O. But with different constraints. I used mutexes, again they they asked why mutexes not semaphores ? what advantage you will get by using mutexes? After producing H2OH2O in three different constrained way they asked me a basic question, lets say CPU generated a virtual address, now you tell us complete steps to get the data (structured, conceptual, practical question ) . It looks simple but while answering the question they asked about TLB and its use, memory heirarchy, then different types of cache memories, physically addressed and virutally addressed cache, how page translation is done, what happens if page fault occurs, why interrupt is used when page fault occurs, concept of virtual memory and its use etc. I explained all steps with diagram by taking examples. Then they asked about thrashing, Page replacement and Belady’s anomaly, example where FIFO algorithms shows Belady’s anomaly.

Then they asked a bit more about virtual memory.

After OS they shifted to RDBMS, they started with why we require normalization and what all concepts you learnt in B.Tech. Then they asked me to write a nested SQL query to fetch some data ( I remember it was lengthy ). Then they asked about locking mechanism in database, how locks are implemented in any database, what data structures are to be used to implement locks and some questions related to transactions.

Next they started with C. Process image in RAM when program is loaded ,basics of all four segments and what they contain ,what is an extern variable and its use,storage class of global variables,how to define structures in C ,represent a rectangle using structures in 2D coordinate system then using this structure to write a program in C to check whether two rectangles are overlapping or not .I defined rectangle initially four points but they asked to improve it, further I changed it to origin points, length and breadth. Then I wrote the function to check the overlapping.

Overall, interview was pretty nice.I answered most of the questions. There were very few places where I was stuck and wherever I was unaware of the exact answer I said sorry. Like they asked me about convex hull and I was not much sure about that so straight forward I said sorry.

My basic strategy was to stay calm, listen to the question carefully and to think before answering even if the question may seem very easy. I used the given paper sheets to draw diagrams, write examples. Whenever it was needed I explained the things by showing steps and sequence on paper. I related my learnt concepts with real life as well as other subjects, like COA with OS, Transactions with shared memory access etc. Throughout the Interview the panel will help you .When you get stuck they will try to point in correct direction so that you can rectify yourself.

Thank you for your utmost patience to give it a read.I hope this small piece of my experience will be of some help to the aspirants. All the best !!

I will be posting some other contents related to BARC. Feel free to reach me in case any doubts:

https://www.linkedin.com/in/abhilash-bhardwaj-6000b7b4/

www.facebook.com/abhilashbhardwaj.kasap

posted Mar 18, 2020
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