This is a request for the completion of a quiz on the subject of
Operating Systems. The quiz will be posted here on September 22st @ 1:00
PM EDT. The expert will have 90 minutes until 2:30 PM EDT to deliver
their solutions. I have attached a guideline document that outlines what
topics are covered on the quiz with some sample questions.
OS QUIZ Guide Operating Systems Quiz Guidelines Topics covered Definitions: ● Operating system, Job, Batch system, Timesharing, Thread, Address space, Process, Context switch, Uniprogramming, Multiprogramming, Multithreading, Multiprocessing, Multitasking, Master boot record, System call, User mode, Kernel mode, Starvation, Atomic operation, Race condition, Mutual exclusion, Critical section, Safety, Liveness, Fairness, Busy Waiting, Semaphore Short answers: ● Benefits of concurrency, Program vs. process, Dispatching loop, Thread state diagram, Amdahl’s law, Booting sequence, System call sequence, Process creation, Preemptive vs. nonpreemptive scheduling, FIFO, RR, SJN, SRTF, Multilevel feedback queues, Lottery scheduling, Independent threads, Cooperating threads, Decision tree, Ways to implement locks, Semaphores vs. integers, Two uses of semaphore, Code verification (producer/consumer) Programming: ● Shell, Write a simple C program (ex. I/O redirection, background processing, spawning a child process, etc.) Sample Quiz Questions ● Suppose 40% of a program can be executed in parallel. What is the maximum speedup for a computer with 4 cores ? ____________________________________________________________________________ __ ● How does a thread transition from the running state to the ready state? Check all answers that apply. a timer interrupt arrives an I/O request is completed a thread voluntarily yields a thread issues an IO request ____________________________________________________________________________ __ ● The following is a modified solution for the consumer-producer problem, with a bounded buffer. Does the solution work? semaphore nLoadedBuffers = 0; // consumer waits on 0 semaphore nFreeBuffers = N; // producer waits on 0, N >= 2 semaphore mutex = 1; // mutex for the buffer Producer() { 1. P(nFreeBuffers); 2. P(mutex); 3. // if space is available, put 1 item in the buffer 4. V(mutex); 5. V(nLoadedBuffers); } Consumer() { 6. P(nLoadedBuffers); 7. P(mutex); 8. // if something in the buffer, take 1 item from the buffer 9. V(nFreeBuffers); 10. V(mutex); } ____________________________________________________________________________ __ ● What are some problems with the following lock implementation? Please check all answers that apply. Lock::Acquire() { // disable interrupts } Lock::Release() { // enable interrupts } They are not atomic. They do not work on multicore machines They cause busy waiting. They may prevent the dispatcher loop to regain control. ____________________________________________________________________________ __ ● Assuming both threads are running in the same address space sharing variables x and y, what are the possible final value pairs of x and y? Please check all answers that apply. (2,2) (1,2) (2,3) (3,2) // Thread A x = 1; x = x + 1; // Thread B y = 1; y = x + 1; ____________________________________________________________________________ __ How are semaphores different from integers? check all answers that apply. Semaphores are accessed through P() and V() operations Semaphores use only positive integers. Semaphore operations are atomic. ____________________________________________________________________________ __ ● Suppose we have three processes: Process ID Required CPU time Arrival Time 1 400 msec 0 msec 2 300 msec 150 msec 3 200 msec 50 msec For the FIFO scheduling, what is the turnaround time of process 1? For the SRTF scheduling, what is the wait time of process 2? For the SJF scheduling, what is the response time of process 2? Assume the time slice of 100 msec and a zero context-switching cost. For the round-robin scheduling, what is the wait time of process 3? What is the turnaround time of process 3 ? ____________________________________________________________________________ __ ● Write a C program that creates (or spawns) a child process to execute Unix's command (echo) with a string as the command-line argument.