One Convergence Interview Experience 2015

Written Test:
I  had 5 sections (1.CN 2.C 3.OS 4.Java 5.Algo and DBMS), each section had 15 questions and duration was 75 min. There was sectional cutoff and negative marking as well. These were GATE level questions.

Interview was on a later date and had elimination rounds.

Round 1:

1. A new protocol is defined with following header fields : 2 bytes for holding the size of the payload, 2 bits to set the fields, 1 byte to hold the description of the protocol. Create a packet with header and payload and how you would set the flags. Based on the above question explain structure padding and why is it needed.
2.  Given two strings, treat them as parent string and a child string. Check whether the child string is present in the parent string or not. If child string is present in the parent string, then reverse the child string part of the parent string and print the parent string.
3. You do "ping www.google.com" , explain the step-by-step process of how this is implemented in linux and in OSI.
4. For the above question, he asked how would it happen if there were VLAN's.
5. What is NAT, why you need it and what is static NAT and dynamic NAT.

Round 2:

1. Tell me about yourself.
2. What is the difference between mutex and semaphore.
3. When you use mutex and when you use semaphore.
4. Write a program using mutex and semaphores
5. How you achieve synchronization in DB.
6. Where do you use trees in real world?
7. Tell me different stages of compilation and give an example of what happens at each stage.
8. Program to reverse linked list.

Round 3:

1. There was a program written on board with all the storage classes in it and asked me to explain each statement in it with respect to C program memory layout.
2. What happens when i call a recursive function indefinitely
3. Why does stack overflow happen.
4. What data structure will you use to implement a routing table and why did i choose it. 
5. What is the time complexity of all quicksort. Is there any sorting technique with a better, worst case time complexity. Which would you prefer quick sort or mergesort and why did i prefer it.
6. What is IPC. What would you use to make it happen.
7. How will you create a child process and a thread.Where are threads created and where are child created. How are they different from one another.
8. What is segmentation fault and how does it occur.
9. When you initialize a variable and later access it, will there be any context switching from user mode to kernel mode. If segmentation fault occurs at this point of time, what part of the kernel detects it.
10. What would you do to reduce the context switching from user to kernel modes.

Note:

      In my resume i mentioned CN, DS and OS as my areas of interest. So all the questions were based on them. In all, i was interviewed for 3 hrs. After every round HR will take you to next panel and during this time he will make small talk, i believe that was the HR round. Also they might ask questions from your written test, though they dint ask me any.

Source: Srikanth K(M.Tech(2014-16))