Answer the following questions clearly but concisely. 1. Whatismultiprogramming? 2. WhatisthekernelofanOS? 3. Whatisthekeydifferencebetweenatrapandaninterrupt? 4. Whatisthepurposeofsystemcalls,andhowdosystemcallsrelatetotheOS andtotheconceptofdual‐modeoperations? 5. NamefivemajoractivitiesofanOSwithrespecttoprocessmanagement. 6. Canaprocessgodirectlyfromreadytoblocked?Explain. 7. Can a process go directly from blocked to running? Explain. 8. Whatarethetwoseparateandpotentiallyindependentcharacteristics embodiedintheconceptofprocess? 9. Whatresourcesaretypicallysharedbyallofthethreadsofaprocess? 10. What is the biggest advantage of implementing threads in user space? What is the biggest disadvantage? 11. In a system with threads, is there one stack per thread or one stack per process when user-level threads are used? What about when kernel-level threads are used? Explain. 12. Can two threads in the same process synchronize using a kernel semaphore if they are implemented by the kernel? What if they are implemented in user space? Discuss your answers. 13. Whatisusuallythecriticalperformancerequirementinaninteractive operatingsystem? 14. Whatarethemedium‐termscheduleranditsmaindifferencefromlong‐ termscheduler? 15. Whatisthedifferencebetweenturnaroundtimeandresponsetime? 16. Whatisthedifferencebetweenpreemptiveandnonpreemptivescheduling? 17. Describetheround‐robinschedulingtechnique. 18. Whichtypeofprocessisgenerallyfavoredbyamultilevelfeedbackqueuing scheduler–aprocessor‐boundprocessoranI/O‐boundprocess?Briefly explainwhy. 19. Five jobs are waiting to be run. Their expected run times are 9, 6, 3, 5, and X. In what order should they be run to minimize average response time? (Your answer will depend on X.) 20. Whatoperationscanbeperformedonasemaphore? 21. A computer has six tape drivers, with n processes competing for them. Each process may need two drives. For which values of n is the system deadlock free? Explain your answer. 22. A system has p processes each needing a maximum of m identical resources and a total of r resources available. What condition must hold to make the system deadlock free? 23. Two collaborating processes run concurrently in a computer system. Assumingthateachofthe10instructionsa‐jisatomic,listallthedifferent possiblepairsofoutcomes(forxandy)thatcanbeproducedbythiscode fragment. Show each sequence and outcome. The shared variables x and y bothareinitializedto0,andthebinarysemaphoremutexhasinitialvalue1. Process1 a) x = 1 b) wait(mutex) c) y = y + x d) x = 2 e) signal(mutex) Process2 f) x = x + 2 g) wait(mutex) h) y = y - 1 i) x = x - y j) signal(mutex) 24. Suppose that there are two types of philosophers in the dinning philosophersproblem.Onetypealwayspicksuphisleftforkfirst(a“lefty”), andtheothertypealwayspicksuphisrightforkfirst(a“righty”).Provethe following: a. Anyseatingarrangementofleftiesandrightieswithatleastoneofeach avoidsadeadlock. b. Anyseatingarrangementofleftiesandrightieswithatleastoneofeach preventsstarvation. 25. Writeabounded‐buffermonitorinwhichthe(int)buffersareembedded withinthemonitoritself. 26. ConsiderasystemconsistingofprocessesP1,P2,...,Pn,eachofwhichhasa unique priority number. Write a monitor that allocates three identical line printers to these processes, using the priority numbers for deciding the orderofallocation. Hint:Youmayusethefollowingstructureforyoursolution: monitor printers { …; //anything you want to add void request_printer(int proc_number){…} //you need to implement void release_printer(){…} //you need to implement } Notes: (1) You may consider the monitor is used to provide a synchronization mechanismforprocessestogetaccesstotheprintersunderthegivenconstraint. (2) When a process is awakened, the condition has to be checked before it is allowed to access a printer. If the condition is not satisfied, the awakened processwillbeblockedagain.(3)Youmayassumethatthereisaglobalfunction for sorting sort() and also others like allocate_printer() and deallocate_printer()availableforusewhenneeded. 27. Howcanthehold‐and‐waitconditionbeprevented? 28. Explainthedistinctionbetweenarealaddressandavirtualaddress. 29. Whatisthedifferencebetweenapageandaframe? 30. Consider a system in which memory consists of the following hole sizes in memoryorder:10KB,4KB,20KB,18KB,7KB,9KB,12KB,and15KB.Which holeistakenforsuccessivesegmentrequestsof (a)12KB (b)10KB (c)9KB forfirstfit?Nowrepeatthequestionforbestfit,worstfit,andnextfit. 31. Acomputerwitha32‐bitaddressusesatwo‐levelpagetable.Virtual addressesaresplitintoa9‐bittop‐levelpagetablefield,an11‐bitsecond‐ levelpagetablefield,andanoffset.Howlargearethepagesandhowmany pagesarethereintheaddressspace? 32. Suppose that a machine has 38-bit virtual addresses and 32-bit physical addresses. (a) What is the main advantage of a multilevel page table over a single-level one? (b) With a two-level page table. 16KB pages, and 4-byte entries, how many bits should be allocated for the top-level page table field and how many for the next-level page table field? Explain. 33. Suppose that a 32-bit virtual address is broken up into four fields, a, b, c, and d. The first three are used for a three-level page table system. The fourth field, d, is the offset. Does the number of pages depend on the sizes of all four fields? If not, which ones matter and which ones do not? 34. It has been observed that the number of instructions executed between page faults is directly proportional to the number of page frames allocated to a program. If the available memory is doubled, the mean interval between page faults is also doubled. Suppose that a normal instruction takes 1 microsec, but if a page fault occurs, it takes 2 msec to handle the fault. If a program takes 60 sec to run, during which time it gets 15,000 page faults, how long would it take to run if twice as much memory were available? 35. Can you think of any situations where supporting virtual memory would be a bad idea and what would be gained by not having to support virtual memory? Explain. 36. A system uses four physical memory frames and the following reference stringoversix pages:1,2,3,4,2,1,4,6,2,1,2,3,5,6.Assumingmemory starts empty, how many page faults will occur and what will be the final contentsofmemoryundertheFIFOpagereplacementpolicy? 37. Isbusywaitingalwayslessefficient(intermsofusingprocessortime)thana blockingwait?Explain. 38. Provide the detailed steps involved in performing an output operation in a systemthatusespolling. 39. Whataretheadvantagesofusingdirectories? 40. Listandbrieflydefinethreefileallocationmethods.