CS 3451 Introduction to Operating Systems question paper, April/May 2024

• (i)What is the main difficulty that a programmer must overcome in writing an operating system for a real-time Environment?(7)
• (ii)Describe three general methods for passing parameters to the operating system.(6)

• (i)Consider a computing cluster consisting of two nodes running a database. Describe two ways in which the cluster software can manage access to the data on the disk. Discuss the benefits and disadvantages of each.(7)
• (ii)List five services provided by an operating system, and explain how each creates convenience for users. In which cases would it be impossible for user-level programs to provide these services? Explain your answer.(6)

• (i)Describe how processes are created and terminated in an operating system.(7)
• (ii)Give an example of a situation in which ordinary pipes are more suitable than named pipes and an example of a situation in which named pipes are more suitable than ordinary pipes.(6)

• (i)Describe how deadlock is possible with the dining-philosopher's problem.(7)
• (ii)Consider the following snapshot of a system. (2+2+2) [Table: Allocation (ABCD) / Max (ABCD) / Available (ABCD): T0 0012 / 0012 / 1520; T1 1000 / 1750; T2 1354 / 2356; T3 0632 / 0652; T4 0014 / 0656] Answer the following questions using the banker's algorithm: (1) What is the content of the matrix Need? (2) Is the system in a safe state? (3) If a request from thread T1 arrives for (0,4,2,0) can the request be granted immediately(6)

• (i)Explain the difference between internal and external fragmentation.(7)
• (ii)On a system with paging, a process cannot access memory that it does not own. Why? How could the operating system allow access to additional memory? Why should it or should it not?(6)

• (i)Illustrate how pages are loaded into memory using demand paging.(7)
• (ii)Under what circumstances do page faults occur? Describe the actions taken by the operating system when a page fault occurs.(6)

• (i)Is disk scheduling, other than FCFS scheduling, useful in a single-user environment? Explain your answer.(7)
• (ii)Describe three circumstances under which blocking I/O should be used. Describe three circumstances under which nonblocking I/O should be used.(6)

• (i)Consider a file system in which a file can be deleted and its disk space reclaimed while links to that file still exist. What problems may occur if a new file is created in the same storage area or with the same absolute path name? How can these problems be avoided?(7)
• (ii)Contrast the performance of the three techniques for allocating disk blocks (contiguous, linked, and indexed) for both sequential and random file access.(6)

• (i)Describe four virtualization-like execution environments, and explain how they differ from "true" virtualization.(7)
• (ii)Why are VMMs unable to implement trap-and-emulate-based virtualization on some CPUs? Lacking the ability to trap and emulate, what method can a VMM use to implement virtualization?(6)

• (i)Describe the three types of traditional hypervisors.(7)
• (ii)Discuss about the mobile operating system with suitable example.(6)

Assume that a program has just referenced an address in virtual memory. Describe a scenario in which each of the following can occur. (If no such scenario can occur, explain why)

• (i)TLB miss with no page fault
• (ii)TLB miss with page fault
• (iii)TLB hit with no page fault
• (iv)TLB hit with page fault

(3+4+4+4)

Apply the (i) FIFO, (ii) LRU, and (iii) optimal (OPT) replacement algorithms for the page-reference strings: 4, 2, 1, 7, 9, 8, 3, 5, 2, 6, 8, 1, 0, 7, 2, 4, 1, 3, 5, 8 Indicate the number of page faults for each algorithm assuming demand paging with three frames.

(5+5+5)