Linux/Unix Operation System Interview for senior professionals. 

Dear professionals. Please use the comment section to answer the questions.

1. Explain 32bit vs 64bit Operating systems of Linux.
2. Explain configuring virtual machines for Super User in Linux
3. Differentiate Copy on write vs illegal access in Unix
4. How do you de-reference ioremap addresses in Linux?
5. Explain in detail about Linux Boot Process.
6. Explain the main difference between completion variables and semaphores
7. Explain the difference between OS scheduling and RTOS scheduling
8. How many threads can be created in one process in Unix?
9. How do you find size of directory in Linux?
10. What is the command used to count number of character in a file in Linux
11. How to check whether specific library is installed or not in my system?
12. How to Dual boot between Fedora 9 and Ubuntu 11.10
13. What is the command used in Linux to lock User password
14. How to find the reason for a dead process without log file on Unix?
15. How do you interact with disks or cd-roms in Protected Mode?
16. Explain how do you run a program in background in UNIX?
17. Without using the /proc filesystem, how can you tell if a given PID is running?
18. Is it possible to completely manage the life cycle of a process and its forks?
19. What is the difference between Process Priority and Thread Priority
20. How do you raise a signal with handlers registered on multiple processes in Unix?
21. What is the difference between Software traps vs Hardware Traps?
22. What is Web Browser Boot-Only Operating System
23. What decides the size of virtual address space available for a process?
24. What do you mean by PID File?
25. What do you mean by memory interlock?
26. Explain the difference between a Cron and a Anacron.
27. Which processes write to /var/adm/messages?
28. What do you mean by a file having 644 permission in Linux?
29. Explain how do you sort output of a command in reverse order in Linux?
30. What is the command used to change the attribute of any file in Unix?

Read More »

Core Computer Science Interview Questions expected in top most companies. 

Algorithm and Computer Programming Languages Interview Questions.

For any Computer Science Graduate seeking a job, algorithm and programming language knowledge is a must. C, C++ are the preferred languages on which questions will be asked. Please use the comment section to answer.

1. Write a C Program module for calculating the factorial of a number using/without using*recursion? 
2. Why is it suggested not to use malloc() or calloc() in C++ for memory allocation? 
3. Can array name itself be used as a pointer? How? 
4. Write a C Program module for finding the first n terms in a Fibonacci Series using/without using recursion? 
5. Find the GCD of two numbers using C/C++? 
6. What do you know about Type Casting? 
7. What’s the use of pointers? Any disadvantages? 
8. What is the difference between basic building blocks in C and C++? 
9. What are time complexity and space complexity? 
10. What is the use of Recursion? Is it compiler-friendly? 
11. How do you find out if a number is a power of 2?
12. Is pointer a variable? 
13. Why java does not contain pointers? 
14. What are constructors and destructors? Then, what do you mean by Virtual Destructors? 
15. What do you mean by malloc() in C? Then, what is dealloc()? (Beware, the interviewer may mislead you by invalid keywords or so) 
16. Write a C Program module to reverse a string, without using string.h library functions? 
17. What is cascading of operator? 
18. What are the basic features of OOP? (Students are advised to study the details of all the basic features of OOP, as this is a very much repeated question in almost all technical interviews. Hence, in this document, further questions regarding each feature of OOP is not included – it’s to be learned as such) 
19. Differentiate between POP and OOP? 
20. What are the differences between Syntax, Logical and Run Time errors in C? 
21. How to convert decimal number to binary? (You need not write the code module, but explain the algorithm) 
22. Why is the complexity of an algorithm to be determined? 
23. How the compiler make difference between C and C++? 
24. What do you mean by the robustness of a language? 
25. What’s the use of Scope resolution operator? 
26. What is the general strategy for Markov Algorithm? 
27. How many temporary variables is essential for swapping two integer variables? (Usually,we use one temporary variable; but it’s not essential. Hence the answer is ZERO. Find out how you can swap without using temporary variables) 
28. What is the difference between = and == in C? 
29. How many but combinations are possible in a byte? 
30. What are function overloading and operator overloading? Which concept of OOP do they comply with? 
31. What are friend functions in Class? 
32. Why do we declare some functions are virtual in Class? 
33. How do you explain to a kid the concept of Classes and Objects? -OR- Can you find an analogy of Classes and Objects in the real world? 
34. What shall be the output of the following code: 
35. int i=50; printf(“%d,%d”,i,i++); 
36. (Yes, sometimes, this also has happened. When they feel that the candidate is appealing,they will give you a small program code in writing, which be tricky in nature. In the above question, the answer is 51,50 which may be wrongly-attempted by the candidates) 
37. Write a C Program module to find the numbers between 10 and 99 where the number is thrice the sum of its digits? 
38. What is Virtual Destructor? 
39. Can a pointer be pointed to by another pointer? 
40. What if I say an 1-D array of pointer is enough to point to a 2-D array of numbers, will you agree with me? Explain. 
41. Can you give me an example for a tertiary operand used in C? 
42. Why we follow top down approach in C-language and bottom up approach in C++?Explain in detail. 
43. Write a function in C/C++ to reverse the words in the sentence, for example "I am from CEC" becomes "CEC from am I" 
44. Can you give me an instance where we may need to resort to 3-D array representation,instead of confining to 2-D?

Read More »

Core Computer Science Interview Questions on Compiler Design.

These questions on Compiler Design can be expected in a freshers job interview.

1. Can you differentiate between ‘syntax analysis’ and ‘semantic analysis’ during compiler design?
2. In simple words, what shall be the basic difference between top-down and bottom-up parsing?
3. Can you say something about type checking and its importance?
4. What is meant by syntax analysis and lexical analysis?
5. What is the need for Symbol Table in Compilers?
6. What is three address code?
7. What are the conflicts that can occur in shift-reduce parser?
8. What is the use of backpatching?
9. What do you mean by Cross-Compiler?
10. What is constant folding?
11. What is a syntax directed definition?
12. Explain about the issues in the design of code generator.
13. What is the difference between DFA and NFA?
14. What do you mean by a synthesized attribute
15. Define annotated parse tree.
16. Explain dangling reference with an example.
17. What are the conflicts that occur in shift-reduce parse?
18. What is the difference between a loosely coupled and tightly coupled system?
19. What do you mean by a assembler? Explain it types.
20. What is the fundamental difference between a ‘compiler’ and an ‘Interpreter’?
21. Define the terms patterns, lexeme and token.
22. Can you list some of the lexical errors.
23. Define ambiguous grammar.
24. Which of the two – linker, loader – is essential in a microcomputer? Can you justify your answer?
25. How is Code optimization done using DAG?
26. What do you mean by data flow analysis? Explain with examples data flow abstraction.
27. What are the functions performed in synthesis phase of a compiler?
28. What are the techniques involved in loop optimization?
29. Explain what are the advantages of LALR parsing over SLR and CLR methods? 
30. What are the components of context free grammar?
31. What is a annotated parse tree?
32. Can you construct a DAG for the expression a=b*-c + b*-c 
33. What do you meant by data-flow engine?
34. What are the different methods employed by Parser to recover from a syntactic error?
35. Explain in brief how is the syntax tree constructed?
36. What are optimizing compilers?
37. Translate the arithmetic expression a * - (b + c) into a syntax tree.
38. Name two compiler construction tools.
39. What is a postfix notation? Explain.
40. Explain what are the techniques involved in loop optimization.

Dear users. Please use the comment section for feedback and answers.

Read More »

Discrete Mathematics and Computational Structures Questions.

Core Technical Interview Questions for Computer Science/IT Students.

1. Do you think Dijisktra’s Algorithms is flawless to find out the shortest path?
2. Are trees and graphs are relevant in computing? Where are they used?
3. Give an example of a Monoid. 
4. Define the degree of a vertex in a graph.
5. If X = {1, 2, 3}, Y = {3, 4}. Find X x Y.
6. What do you mean by an equivalence relation?
7. Explain ‘Pigeon Hole Principle’?
8. What is a spanning tree?
9. Explain what do you mean by a Hamiltonian circuit?
10. What’s the difference between a complete binary tree and full binary tree?
11. What do you mean by a ‘regular graph’?
12. Define equivalent Finite State Machines
13. Give an example of infinite sequence.
14. Explain what do you mean by finite state machine.
15. Define lattice and a weighted graph.
16. Explain what do you mean by a minimum spanning tree.
17. What do you mean by BNF notation?
18. Prove that ((a->b) ^ (b-> c)) -> (a -> c) is a tautology
19. What is the difference between a graph and a tree?
20. Do you know about the Traveling Salesman Problem?
21. Find the distance between x = 1101101 and y = 0001011.
22. Define isomorphic graph and a connected graph
23. Please provide an example of infinite sequence
24. Have you heard about Graph Coloring Problem with Minimal number of Colours?
25. Can you provide an example of empty set

Read More »

Computer Network Questions for Networking Professionals.

1. Explain in brief about the concept of routing protocol?
2. What are the activities the routing protocol perform?
3. Explain about intra-domain and inter-domain routing protocols?
4. Describe internet work and intranet work routing protocols?
5. What is the method routing protocol use to determine shortest path?
6. Explain in brief about the distance vector routing protocol?
7. What do you mean by Active and Passive route?
8. What is OSPF. Explain?
9. Can you tell me how do routers share information in Distance Vector routing?
10. Explain the process of count-to-infinity problem in distance vector?
11. Explain metric or the cost calculated for Distance Vector routing protocol?
12. Describe the working process of Link-State routing protocols?
13. Explain in brief the concept of broad cast and multi-cast?
14. Differentiate between distance vector and link-state protocol?
15. Describe how does OSPF populate route table?
16. Can you tell me what are the different tables in OSPF?
17. What are the metrics are used by routing protocols to determine the best path?
18. Explain and differentiate interior and exterior routing protocols?
19. Explain in brief the different areas in OSPF?
20. Describe the different router types in OSPF?
21. Explain Designated Router and Backup designated router?
22. Can you tell me what are different types of dynamic protocols?
23. Explain in brief about the autonomous numbers in EGP?
24. What do you mean by BGP?
25. Explain the concept of BGP speakers and Peers?
26. What do you mean by EBGP and IBGP?
27. What do you mean by RIB?
28. What are the different different router states in OSPF?
29. Explain different OSPF packet types?
30. Describe how SPF algorithm does the route determination?
31. Explain what do you mean by autonomous system?
32. What is the concept of BGP confederations?
33. What do you mean by BGP path attributes?
34. Explain how are routing neighbors discovered in BGP?
35. Describe how BGP does the decision process?
36. What do you mean by a Firewall?
37. Explain the different types of firewalls?
38. Explain in brief packet filtering firewall?
39. What do you mean by a circuit level gateway?
40. What do you mean by a bastion host?
41. Explain the different types of firewall architectures?
42. Explain dual home architecture?
43. What do you mean by a Application Gateway?
44. Is NAT a firewall?
45. Explain in detail about the screened subnet architecture?
46. What do you mean by IP spoofing and how can it be prevented?
47. Differentiate between trusted and untrusted networks?
48. Differentiate between Symmetric and Asymmetric crypto-system?
49. Can you tell what are the different symmetric algorithms available for computer networks?

Read More »

Computer Networks Interview Questions for CS/IT Students.

• What are the disadvantages of symmetric algorithms?
• What are the different asymmetric algorithms?
• What is a digital certificate?
• Can you explain what IPSec is?
• Can you give an overview of various components in IPSec?
• Can you explain in a generic manner the packet of IPSec?
• Can you describe the Authentication Header (AH) Protocol?
• What do you mean by SSL? Why is it used?
• Can you explain what the use of IGMP Protocol is?
• How do you continuously ping an IP Address?
• Can you explain RPC (Remote Procedure Calls)?
• Can you explain TCP IP Protocol?
• Can you explain the architecture of TCP IP Protocol?
• Can you explain TCP header in detail?
• Can you explain the concept of CDMA?
• Can you explain the concept of DHCP?
• How does DHCP work?
• How can we configure DHCP?
• What is DNS?
• What is a difference between a domain and workgroup?

Dear job-seekers. Please use the comment section for answers. Thank you !!

Read More »

Automata Theory Tutorials and Download Links.

1. Overview of Automata Theory (ps and pdf )
2. Finite Automata Tutorials(ps and pdf )
3. Regular Expressions and Regular Grammars Tutorials(ps and pdf )
4. Pumping Lemma Tutorials(ps and pdf )
5. Minimizing DFA Tutorials (ps and pdf )
6. Tutorials on Automata Theory
7. Context-free grammars Tutorials(ps and pdf )
8. Transforming Grammars Tutorials(ps and pdf )
9. Pushdown Automata Tutorials(ps and pdf )
10. Parsing Tutorials(ps and pdf )
11. LR Parsing Tutorials(ps and pdf )
12. LL Parsing Tutorials(ps and pdf )
13. Properties of CFL (ps and pdf )
14. Turing Machines Tutorials(ps and pdf )
15. Turing Machines as Building Blocks Tutorials(ps and pdf )
16. Theory of computation Tutorials and Lectures
17. Turing Machines Tutorials(ps and pdf )
18. Recursively Enumerable (ps and pdf )
19. L-Systems Tutorials(ps and pdf )
20. Decidability Tutorials(ps and pdf )
21. Compilers Tutorials(ps and pdf )

Read More »

Advanced OS Interview Questions asked in Microsoft, Google.

• How do you Check status of process and restart process if unresponsive/stopped
• Architecturally what is the difference between a shared object (SO) and a dynamic link library (DLL)?
• Are there memory leaks in Linux?
• Are Unix/Linux systems vulnerable to leaking global kernel objects?
• Can you determine if you am on Win7 OS from VB6?
• Can synchronous I/O be canceled automatically even if the driver doesn’t complete irp?
• Difference between embedded Operating system and Desktop Operating System
• Does every function end up in kernel mode?
• Examples of inter process communication(IPC)
• How can you find whether a process is in deadlock or is waiting for I/O
• How do you delete a folder that gives me this error dialog: Folder Access Denied. You need permission to perform this action
• How Find Executable References programatically
• How to figure out a program’ network and system resource usage behaviour?
• How to get the key state via a scancode (not virtual keycode)?
• How to know which file is opening in Computer using C#
• Is there a ”free” way for testing on different OSes?
• How do you Run Software as Exclusive Shell Application?
• Whats the difference between Thread ID vs. Thread Handle
• What happens when two processes on the same computer communicate via TCP?
• What happens when we plug a piece of hardware into a computer system?
• What is the difference between DETACH_PROCESS and CREATE_NO_WINDOW process creation flags for createProcess function
• What is the difference between user variables and system variables?
• What resources would you recommend for learning about OS security?
• Which characters are safe to name files and directories with?
• Why are ”Executable files” operating system dependent?
• How to get OS version number?
• Question on Windows XP – How to get the name of OS in which the code is running using C#?
• How can you show operating system info through c# code

Read More »

Technical Interview on Computer Architecture and Organization, System Programming

1. What’s the importance of Subroutines in Programming? Which data structure is widely used in Subroutine concept?
2. What do you mean by Software interrupts?
3. What is pseudo-parallelism?
4. What are the functions of Program Counter and Stack Pointer?
5. What dimension of memory is RAM?
6. Why do we use cache?
7. Define DMA?
8. What is Process Interleaving?
9. Tell me how you will replace a BIOS battery?
10. Differentiate RISC and CISC?
11. Out of Intel Core 2 duo and Dual Core, which one is more efficient?
12. Which is the newest series of processors from Intel, available for the common public?
13. What are DDR2 and DDR3?
14. Can you explain how the execution of an instruction is done, in detail?
15. What is the difference between static and dynamic memories?
16. What do you mean by vectored interrupts?
17. Which one – linker or loader – is essential for a computer? (Ans: loader. It’s essential that data to be processed (OS+Data) to the functional memory unit. For this loader is a must. Linker’s idea is different from this basic need)
18. What do you mean by relocatability of a program?
19. What do you mean by a macro?
20. What do you mean by pipelining?
21. Explain the concept of virtual memory?
22. What is write back and write through caches?
23. What is miss penalty and give your own ideas to eliminate it.
24. What is aliasing?
25. What is the difference between a latch and a flip flop?
26. What is the race around condition? How can it be overcome?
27. What is meant by Snooping Cache?
28. Explain how to convert a number into its 2’s complement and convert back.
29. Explain about various hazards?

Read More »

Technical Interview Questions for CS/IT Students asked in Infosys.

The below questions are related to Software Engineering. Please use the comment section for the answers.

1. What do you mean by CMM level? Do you know what CMM level we possess?
2. Suppose you are automating the library of your college. Which model would you adopt?
3. Which of the three – design, coding, implementation and maintenance – do you think is of utmost importance?
4. Can you tell me something about COCOMO?
5. Suppose in your company there was a dispute in terms of technical enhancements of the firm. There are around 25 employees taking part in the dispute. Which method would yourely on to sort out the dispute? (student is supposed to have some basic knowledge in activities like brain storming, questionnaire, etc. It’s suggested that they go through B.Tech First year TCSS’ relevant topics)
6. Which process model do you think is the best? Justify (do not blankly say one model is the best; be smart and diplomatic enough to state that each model finds its best role invarious types of software designs. Cite some examples and justify)
7. Why do you consider an SRS to be of utmost important document in a software project?
8. What does an ER-diagram represent?
9. Which are the different phases in a software life cycle?
10. What do you mean by a Good Software Design?
11. How do you search and find requirements? What are possible sources?
12. What do you think is the limitation of an E-R diagram?
13. Why are analysis and testing phases very important?
14. Why should you study a theory-based subject like Software Engineering? Is it that much
important for a Software Engineer on field?
15. What do you mean by testing? What is black box testing?
16. What are the objectives of debugging?
17. What is an SRS?
18. How many of the three variables scope, time and cost can be fixed by the customer?Why?
19. Do you think whether documentation is an important activity during a software project?

Read More »

Computer Science : Data Structures Interview Questions.

Students are supposed to be well aware of the programming concepts using Arrays, Linked Lists, Trees and Graphs. It’s likely that the interviewer may provide you with a scrap of paper and ask to write down certain program modules.

• Why do we require data structures?
• What is the difference between a physical structure and a data structure?
• If I say that linked list is a linear data structure, will you assent to me?
• What is the difference between a B Tree and B+ Trees? Have they got any similarities?
• What do you know about AVL rotation?
• What is the last thing you learned about data structures from a book, magazine or website?
• You might have used 2-D arrays while programming. But you know that our main memory is of one dimension. How is it possible to establish this?
• What is FIFO?
• Can you differentiate between Array and Linked List? Which one is linear and what are the advantages being linear?
• What do you mean by a circular queue? Can you suggest a situation where we can use this?
• What do you mean by rear and front end of a queue?
• (This question is normally a continuation of the above question)What if I insert at the rear end and delete from the front end, what will happen?
• Have you ever used priority queues? Where do we use them in practical applications?
• How can a stack be implemented? Which one do you prefer? Why?
• What would you imagine the problems that could happen if the data structures didn’t exist?
• How do you explain what a data structure means, to a 12-year old nephew of yours?
• Suppose you are a teacher and a student comes to you with his ambiguities between databases and data structures. How could you make him understand these two?
• What are activation trees? What is its use?
• Which data structure is used for better performances under insertion and deletion on a dynamic basis?
• What is the Worst Case of “Merge Sort”?
• Where are linked lists used?
• Could you please explain Dijkstra’s Algorithm in brief?
• Is double link list a linear data structure? Why?

Read More »

Operating Systems Interview Questions for Freshers. 

Dear readers and job-seekers. We request you kindly to discuss the answers in the comment section.

1. Can you explain the working of fork() system call?
2. What is the concept of preemption in scheduling?
3. What is the importance of real time systems?
4. Which CPU scheduling algorithm do you think is the best? Why?
5. What do you know about file systems in UNIX and Windows?
6. What does NT stands for in Windows NT?
7. Expand GNU?
8. Tell me something about paging?
9. What are real time systems?
10. What is the concept of Master and Slave at the time of booting?
11. Expand BIOS? What do you know about recent advancements/substitute for BIOS?
(Hint: UEFI. Students are supposed to keep track of such latest advancements in the field,through dailies, internet and magazines. These kinds of hints are not usually given by the interviewer, but sometimes he may try to help you in case you do not answer the question)
12. Are semaphores, monitors, etc. important concept in Kernel Programming? Why?
13. What if I say, as the degree of multi programming increases, CPU usage also increases –do you agree? (Ans: No. It increases first, then steady and then decreases)
14. What are the advantages of threads over processes? Have they got any disadvantages?
15. What is an Operating System?
16. What do you mean by deadlock? Is deadlock possible without the concept of shared memory?
17. What do you know about Process Spawning?
18. Why do we call thread a ‘light-weight process’?
19. What are the conditions for deadlocks?
20. What is meant by Busy Waiting?
21. What does PCB contain, in regard of a process?
22. What is process interleaving?
23. Can you explain ‘Banker’s Algorithm’?
24. Tell me something about disk fragmentation?
25. What do you know about starvation?
26. Is ‘directory’ a file? Explain?
27. Why do we use the concept of paging?
28. Tell me something about Mutual Exclusion?
29. Why page replacement algorithms are required?
30. Can you compare FAT-32 and NTFS? What does this 32 mean?
31. What are the functions of Interrupts?
32. What is done during a booting process?
33. What do you think about dynamic memory allocation?
34. Why do we use virtual memory?
35. What’s the difference between a system call and a system program?
36. Why in most USB Drives FAT is preferred to NTFS?
37. Can you suggest some differences between “Physical Address Space” and “Logical
Address Space”?
38. What is a DRAM?
39. Explain Deadlocks?
40. Differentiate Starvation and Aging?
41. Which is the latest mobile platform introduced by Google?

Read More »

Automata Theory and Languages Questions.

• Where is Myhill-Nerode theorem is used? Could you please explain the algorithm?
•  If I say PDA=FA+2 Stacks, what is FA+3 stacks?
• Every regular language is context free. Do you agree? Why?
• Can you compare a PDA with a microcomputer?
• If I say DFAs are more realistic than NFAs, will you agree with me?
• You know that the closure property exists under concatenation of two regular languages.Now explain: an is regular and bn is regular. But why anbn is not regular?
• If I say some language is context free, what does it imply?
• What would you call the State Diagram of a Process – an NFA or a DFA?
• Explain the concept of valid and invalid alphabets.
• What is the difference between regular grammar and algebraic grammar?
• When do you call a problem decidable?
• What is the difference between (a,b) and (a+b)?
• Differentiate between Palindrome and Reverse function?
• What do you mean by saying that a language is LL(1)?
• What is the difference between PLUS and Kleene Star Closure?
• Explain how to create a RE of a particular language?
• Differentiate between FA and NFA.
• What is Pumping Lemma I and II and what is the difference between pumping Lemma 1 and pumping Lemma 2?

Read More »

· Can you define a protocol?
· Is it compulsory that compression, encryption and translation functions will be used during communication?
· What’s the concept of Simplex, Half Duplex and Full Duplex dialogs?
· Can you explain what an IP address is?
· How many IP addresses can be there in IPv4?

· Can you explain the concept of Unicast IP address?
· Can you explain the concept of IP multicasting or multicast IP address?
· What is Broadcasting in terms of Computer Networks?
· What are the IP address ranges for public and private IP address?
· If the host has the subnet ID why do we need a subnet mask?
· How is network address calculated from the subnet?

· What is the advantage of using classless addressing over classful addressing scheme?
· Why do we need to subtract two from number of hosts in all IP Classes, to get the effective number of hosts?
· Can you explain the concept of VLSM?
· Can you explain IP packet in detail?
· Can you explain the concept of DPU, Segments, Datagram, Frame and packet?

· What is IP datagram fragmentation and MTU?
· Larger the IP datagram less the overhead, is it true or false?
· What is the minimum size of MTU bytes?
· Can you explain how optimal MTU size is calculated?
· How does the IP message finally reassemble?

· On what layers do router, switches, bridges and hubs operate?
· What are the basic components of the router?
· Can you explain the concept of TTL?
· What is the concept of ICMP packets?
· Can you explain the concept of NAT?
· How is NAT implemented?
· What is the concept of routing tables?

· What is the use of route print?
· Can you explain how a routing table looks like?
· Can you explain the concept of static and dynamic routing?
· When to use Static routes and dynamic routes?
· What is the difference between Source-Routing and Router-Routing?
· Can you explain static default routes?
· What is the advantage of using Static default routes?
· Why do workstations have route tables?

Read More »