| OPERATING SYSTEM |
| PAPER NO. 4 |
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| CS-202 OPERATING SYSTEM (B.Tech 4th Semester,1202) Time : 3 Hours Maximum Marks : 60 NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from Section B and any two questions from Section C Section-A Marks : 20 1(a) A computer has a 24 bit address bus and an instruction format providing 12 bits in the address part. Calculate the maximum addressible memory and the address offset range. (b) Indicate four characteristics which give rise to the wide varitation in the nature of I/O devices. (c) What low level scheduling scheme is best suited to interactive systems ? (d) Writing an OS that can operate without interference from malicious or undebugged user programs require some H/W assistantance . Name three H/W aids to writing an OS. (e) Semaphore waiting lists are often implemented as queues served in FIFO order. Could they be implemented as stacks ? Elaborate. (f) What protection problems may arise if a shared stack is used for parameter passing ? (g) What is an Auidit Log ? (h) How does an Audit Log Act as a differnce to those who would commit a secuirity violation ? (i) What is the difference between a system call and a system program ? (j) Compare the various features of DOS and UNIX. Section-B Marks:5 Each 2. Given 3 page frames, use algorithims : (a) LRU (b) OPT to compute the number of page faults for the following reference string : F A B C A D A E C D A D C B C A B F A B 3. What are the main difficulties in writting an OS for a real time environment ? 4. Comment on the correctness of each of the following with reasons/examples: (a) SRT always has a lower average response time than SJF. (b) SJF is fair. (c) The shorter the job, the better the service it should recieve. (d) Because SJF gives preference to short jobs, it is useful in time sharing. 5. Describe the structure of the UNIX file system. Differentiate between i-node and a direction entry that points to an i-node. 6. Write a note on Privacy and Secuirty of an operating system. Section-C Marks : 10 Each 7. What are the advantages of distributed operating systems ? Compare the distributed operating system with any other non-distributed operating system. 8. What are the four necessary condithions for deadlock ? Describe various methods for deadlock prevention and detection with the help of suitable example. 9. Describe various mechanisms by which we can ensure that the files, memory segments, CPU and other resources can be operated on only by those processes that have gained proper authorization from the OS. |
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