Consider the following set of process with CPU burst time.

Consider the FCFS, SJF Non-Preemptive and Round Robin (Quantum = 6) scheduling algorithms and calculate average waiting time to find which algorithm would give the minimum average waiting time.

Explain the different states of a process in the process life cycle.

Explain how the division of user mode and kernel mode ensures a primary level of system security.

Explain the differences between a monolithic kernel, a microkernel, and a hybrid kernel. What are the advantages and disadvantages of each?

Compare and contrast classical synchronization problems such as the Producer-Consumer, Dining Philosophers, and Readers-Writers problems.

What do you mean by an Operating System? What are the three main purposes of an operating system? Write a short note on, "An operating system is a resource allocator".

Direct memory access is used for high-speed I/O devices in order to avoid increasing the CPU's execution load.
i) How does the CPU interface with the device to coordinate the transfer?

ii) The CPU is allowed to execute other programs while the DMA controller is transferring data. Does this process interfere with the execution of the user programs? If so, describe what forms of interference are caused.

What are two differences between user-level threads and kernel-level threads? Under what circumstances is one type better than the other?.

What advantage is there in having different time-quantum sizes at different levels of a multilevel queueing system? Explain with example.

Suppose that a system is in an unsafe state. Show that it is possible for the processes to complete their execution without entering a deadlocked state.

In a system with a TLB, assume the following:

i) the memory access time is 150 nsec.     ii) the TLB access time is 25 nsec.

iii) the TLB hit rate is 80%.

Compute the effective access time for memory in this scenario.

Define virtual memory. How does it empower computing?

Consider the following page reference string:

2, 3, 2, 1, 5, 2, 4, 5, 3, 2, 5, 2

How many page faults would occur for the following replacement algorithms, assuming three frames? Remember that all frames are initially empty, so your first unique pages will cost one fault each.

i) Least Recently Used (LRU)

ii) Optimal Page Replacement

iii) FIFO

What are the four essential managers of an operating system?

What is a job scheduler? What is a process scheduler?

Use the best-fit algorithm to allocate the memory blocks to the three arriving jobs. Show internal fragmentation (if any) and waiting jobs (if any).

What is deadlock? Describe about necessary conditions for deadlock characterization.

Briefly describe Banker's algorithm.

Draw storage device hierarchy.

Identify all of the deadlocked processes.

Suppose that a disk drive has 5000 cylinders, numbered 0 to 4999. The drive is currently serving a request at cylinder 143. The queue of pending request in FIFO order is 86, 1470, 913, 1774, 948, 1509 ,1022 ,1750,130. Starting from the current head position, illustrate and calculate the total distance (in cylinders) that the disk arm moves to satisfy all the pending requests for each of the following disk-scheduling algorithms.

i. FCFS

ii. SSTF

iii. SCAN (assuming arm movement towards the beginning of disk)

iv. LOOK

V. C-SCAN (assuming arm movement towards the end of disk)

vi. C-LOOK

Draw Gantt Charts for illustrating five scheduling algorithms which are First-Come-First-Served, Non-Preemptive Shortest-Job First, Priority and Round-Robin (time quantum = 1).

We have stressed the need for an operating system to make efficient use of the computing hardware. When is it appropriate for the operating system to forsake this principle and to "waste" resources? Why is such a system not really wasteful?

Direct memory access is used for high-speed I/O devices in order to avoid increasing the CPU's execution load.

i) How does the CPU interface with the device to coordinate the transfer?

ii) The CPU is allowed to execute other programs while the DMA controller is transferring data. Does this process interfere with the execution of the user programs? If so, describe what forms of interference are caused.

Define demand paging and segmentation with examples.

Provide two programming examples in which multithreading provides better performance than a single-threaded solution.

Consider a computer system that runs 5,000 jobs per month and has no deadlock-prevention or deadlock-avoidance scheme. Deadlocks occur about twice per month, and the operator must terminate and rerun about ten jobs per deadlock. Each job is worth about two dollars (in CPU time), and the jobs terminated tend to be about half done when they are aborted.

A systems programmer has estimated that a deadlock-avoidance algorithm (like the banker's algorithm) could be installed in the system with an increase of about 10 percent in the average execution time per job. Since the machine currently has 30 percent idle time, all 5,000 jobs per month could still be run, although turnaround time would increase by about 20 percent on average.

i) What are the arguments for installing the deadlock-avoidance algorithm?

ii) What are the arguments against installing the deadlock-avoidance algorithm?

Given the following system:

-Total of four processes

-Total of three resources (one instance per resource)

-Three process has each one Request Edge to one of the Resources (you decide which one)

i) Draw the resource allocation graph of the System

ii) Is the system you drew in a Safe/Unsafe/Deadlocked state? Justify you answer

Given six memory partitions of 300 KB, 600 KB, 350 KB, 200 KB, 750 KB, and 125 KB (in order), how would the first-fit, best-fit, and worst-fit algorithms place processes of size 115 KB, 500 KB, 358 KB, 200 KB, and 375 KB (in order)? Rank the algorithms in terms of how efficiently they use memory.

Consider the following page reference string:

1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6

How many page faults would occur for the following replacement algorithms, assuming three and four frames? Remember that all frames are initially empty, so your first unique pages will cost one fault each.

• LRU replacement
• Optimal replacement

What are the three main purposes of an operating system?

What is a process in an operating system, and how does it differ from a program? Explain the different states a process can be in during its lifecycle.

Describe process scheduling and the role of the scheduler in managing processes. How do different scheduling algorithms (e.g., FCFS, Round Robin) affect process performance and CPU utilization?

Consider the following set of processes with their respective arrival times and burst times:

Use the Round Robin (RR) scheduling algorithm with a time quantum of 3 units to answer the following questions:

• For Round Robin (RR): Calculate the waiting time, turnaround time, and completion time for each process.
• How does the time quantum affect the waiting time and turnaround time compared to other scheduling algorithms such as FCFS or SJF?
• Compare the performance of RR with a time quantum of 3 units to a time quantum of 2 unit. Which setting provides better system performance and why?

Consider a system with two types of resources (R1, R2) and three processes (P1, P2, P3). The following allocation and request details are given:

Draw the Resource Allocation Graph and determine if the system is in a deadlock state.

Define TLB with diagram. Given the following information about a system with a TLB: Total memory accesses = 1500, Number of TLB hits 1200, Number of TLB misses = 250 Calculate the TLB Hit Rate and TLB Miss Rate.

Consider the following page reference string:

7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 0, 3, 2, 1

How many page faults would occur for the following replacement algorithms, assuming three frames? Remember that all frames are initially empty, so your first unique pages will cost one fault each.

i) MRU (Most Recently Used)
ii) Optimal Page Replacement
iii) Second-Chance (Clock) Page Replacement

Explain the moving-head disk mechanism in operating systems. How does the read/write head of a disk move to access different tracks, and how does this mechanism affect disk performance? Discuss the factors that influence seek time and the different types of disk scheduling algorithms used to optimize disk head movement. Include necessary diagrams.

Answer the following questions using the banker's algorithm:

i) What is the content of the matrix Need?

ii) Define safe and unsafe state. Is the system in a safe state? If so, show a safe order in which the processes can execute.

iii) If a request from process PO arrives for (0,2,0), can the request be granted immediately?

Describe the following with examples:

i) Paging

ii) TLB

Discuss the relationship between hardware, OS, system programs, and application programs.

Define a process. What are the various states a process can be in during its lifecycle?

What is deadlock? Discuss various strategies used to prevent it from occurring.

What is process synchronization, and why is it necessary in a multiprogramming environment? Provide examples of problems caused by lack of synchronization.

In a university's computer lab, two students, Alice and Bob, are writing parallel programs that require access to two shared printers (Printer A and Printer B). Each printer is treated as a non-shareable resource. The following situation occurs:

• Alice acquires Printer A and requests Printer B.
• Bob acquires Printer B and requests Printer A.
• Neither student can proceed because each is waiting for a resource held by the other, and the system does not preempt resources.

i) Identify and explain the four necessary conditions for deadlock. Which of these are satisfied in the above scenario?

ii) Draw a Resource Allocation Graph (RAG) to represent the above scenario. Based on your graph, explain how a cycle implies a deadlock.

iii) Describe how a deadlock detection and recovery approach would handle this situation.

iv) Modify the system such that it uses the Banker's Algorithm. Would the system have entered a deadlock in that case? Explain using a safe unsafe state analysis.

Compare first-fit, best-fit, and worst-fit memory allocation strategies in terms of their impact on fragmentation.

What is segmentation? Consider the following segment table:

What are the physical addresses for the following logical addresses?

i) 0,430   ii) 1,10
iii) 2,500   iv) 3,400

Describe optimal page replacement algorithm for the following reference string 7 0 1 4 2 0 3 0 4 2 3 0 3 2 1 2 0 1 7 0 1. Also calculate the number of page fault for frame size 4.

List five services provided by an operating system and explain how each creates convenience for users.

Describe the differences among short-term, medium-term, and long-term scheduling.

What are the benefits and the disadvantages of synchronous and asynchronous communication? Consider both the system level and the programmer level.

Regarding the Producer-Consumer problem, explain the following term:
i) Producer process   ii) Consumer Process   iii) Unbounded-buffer   iv) Bounded-buffer

Consider the following snapshot of a system:

Answer the following questions using the banker's algorithm:

i) What is the content of the matrix Need?

ii) Define safe and unsafe state. Is the system in a safe state? If so, show a safe order in which the processes can execute.

iii) If a request from process P1 arrives for (0,4,2,0), can the request be granted immediately?

Given memory partition of 100 KB, 500 KB, 200 KB and 600 KB (in order), how would each of the first fit, best fit and worst fit algorithms place processes of 212 KB,417 KB,112 KB and 426 KB (in order)? Rank the algorithms in terms of how efficiently they use memory.

What does TLB stands for? Briefly explain its usage in operating system.

Suppose that a disk drive has 200 cylinders, numbered 0 to 199. The drive is currently serving a request at cylinder 50. The queue of pending requests, in FIFO order, is:

      95, 180, 34, 119, 11, 123, 62, 64

Starting from the current head position, what is the total distance (in cylinders) that the disk arm moves to satisfy all the pending requests? You should also provide a graphical view of head movement for each of the following disk-scheduling algorithms.

i) C-SCAN

ii) LOOK

What is the relationship between turnaround time, CPU cycle time, and waiting time?

As a process executes, it changes state. Complete to draw the state diagram of a process from its creation to termination, including all transitions, and briefly explain functions of each state.

Use the first-fit algorithm to allocate the memory blocks to the three arriving jobs. Show internal fragmentation (if any) and waiting jobs (if any).

Draw and describe address translation architecture.

What is page fault? Draw the steps in handling a page fault.

Can the deadlock be resolved without selecting a victim?

Calculate the turnaround time for each process based on the five scheduling algorithms.

Why do some systems store the operating system in firmware, while others store it on disk?

What are the two essential parts of a process? How is a process different from a program?

Draw storage device hierarchy.

Illustrate how a binary semaphore can be used to implement mutual exclusion among n processes.

Consider the following snapshot of a system where there are five processes PO through p4 and three resource types A (10 instances), B (5 instances), and C (7 instances):

Answer the following questions using the banker's algorithm:

i) What is the content of the matrix Need?

ii) Define safe and unsafe state. Is the system in a safe state? If so, show a safe order in which the processes can execute.

iii) If a request from process PO arrives for (0,2,0), can the request be granted immediately?

Consider a system in which a program can be separated into two parts: code and data. The CPU knows whether it wants an instruction (instruction fetch) or data (data fetch or store). Therefore, two base-limit register pairs are provided: one for instructions and one for data. The instruction base-limit register pair is automatically read-only, so programs can be shared among different users. Discuss the advantages and disadvantages of this scheme.

What is fragmentation? Briefly explain different types of fragmentation in context to operating system.

Compare Monolithic, Layered, Microkernel, and Modular operating system structures. How does each structure organize components, and what are the main advantages and disadvantages? Provide examples.

Explain the concept of process synchronization. Why is it necessary, and what problems can arise if processes are not properly synchronized?

What is inter-process communication (IPC), and what are some common IPC mechanisms (e.g., pipes, message queues, shared memory)? In which scenarios would each mechanism be most appropriate

Explain the difference between user-level threads and kernel-level threads. What are the advantages and disadvantages of each type of thread? Explain with example.

Describe the difference between deadlock prevention, deadlock avoidance, and deadlock detection. Provide examples of techniques used for each approach.

What is paging in an operating system, and how does it manage memory? Explain the role of page tables in mapping logical addresses to physical addresses.

Explain the differences between segmentation and paging in the context of virtual memory management. How do these techniques complement each other?

How do you calculate the disk access time? A disk is advertised with a seek time of 3ms, 512 bytes per sector and 128 sectors per track. The disk rotates at 5, 200 rpm.

• Determine the average rotational delay for the disk.
• Determine the time required to read a 4 Mbyte file. You are to assume that the file occupies sectors on adjacent tracks.

What are the main components in the logical organization of a computer system?

What is a Process Control Block (PCB)? Illustrate and explain its components with a diagram.

Illustrate how a Resource Allocation Graph (RAG) can be utilized to identify deadlocks in a system.

Describe how semaphores are used for process synchronization. Illustrate with an example of the producer-consumer problem.

Consider a system with 1000 KB of memory and processes that require varying sizes of memory blocks. Simulate memory allocation and identify points where fragmentation occurs. How can it be minimized?

Describe the sequence of steps that occur when a virtual address is translated using TLB. What happens in the case of a TLB hit and a TLB miss?

Define following terms: i) CPU Thrashing   ii) RAID

Give two reasons why caches are useful. What problems do they solve? What problems do they cause? If a cache can be made as large as the device for which it is caching (for instance, a cache as large as a disk), why not make it that large and eliminate the device?

What do you know about process and process control block (PCB)? What are the states of process? Explain with necessary diagrams.

Explain the difference between preemptive and non-preemptive scheduling.

The following processes are being scheduled using a Priority Scheduling-Preemptive algorithm. Each process is assigned a numerical priority, with a higher number indicating a higher relative priority.

i) Show the scheduling order of the processes using a Gantt chart.
ii) Fill the following table for exit time, turn-around time, and waiting time:

List two deadlock detection mechanisms. Construct the wait-for graph that corresponds to the following resource allocation graph and determine whether or not there is deadlock.

What is paging? Consider a logical address space of 64 pages of 1,024 words each, mapped onto a physical memory of 32 frames.

i) How many bits are there in the logical address?

ii) How many bits are there in the physical address?

What is fragmentation? Consider the following segment table:

What are the physical addresses for the following logical addresses?

i) 0, 430   ii) 1, 10   iii) 2, 500   iv) 3, 400

Define following terms:

i) Thrashing

ii) RAID

What is deadlock? Describe about necessary conditions for deadlock characterization.

Given that main memory is composed of THREE page frame for public use and that a program requests pages in the following order: 1 2 3 4 1 2 5 1 2 3 4 5.

i) Using the FIFO page removal algorithm, calculate FAILURE RATIO and a page trace analysis indicating page faults with asterisks (*).

ii) Using the LRU page removal algorithm, calculate FAILURE RATIO and analyze a page trace analysis indicating page faults with asterisks (*).

iii) Given that main memory is composed of FOUR page frame for public use and that a program requests pages in the following order: 1 2 3 4 1 2 5 1 2 3 4 5. Let's define most-recently-used (MRU) as a page removal algorithm that removes from memory the most recently used page. Using FIFO and MRU, do the page trace analysis using the same page requests as above and compute the failure ratios.

Use the next-fit algorithm to allocate the memory blocks to the three arriving jobs. Show internal fragmentation (if any) and waiting jobs (if any).

Briefly describe Banker's algorithm.

Explain multistep processing of a user program.
                                        

Which requests by the three processes for resources from R2 would you satisfy to minimize the number of processes involved in the deadlock?

Calculate the waiting time for each process based on the four scheduling algorithms.

How does the distinction between kernel mode and user mode function as a rudimentary form of protection (security) system?

Consider the following set of processes, with the length of the CPU burst given in milliseconds:

The processes are assumed to have arrived in the order P1, P2, P3, P4, P5 all at time 0.

i) Draw four Gantt charts that illustrate the execution of these processes using the following scheduling algorithms: FCFS, SJF, non preemptive priority (a large priority number implies a higher priority), and RR (quantum = 2)

ii) What is the turnaround time of each process for each of the scheduling algorithms

iii) What is the waiting time of each process for each of these scheduling algorithms?

iv) Which of the algorithms results in the minimum average waiting time (over all processes)?

Explain different threading models with sufficient diagrams.

Race conditions are possible in many computer systems. Consider a banking system that maintains account balance with two functions: deposit (amount) and withdraw (amount). These two functions are passed the amount that is to be deposited or withdrawn from the bank account balance. Assume that a husband and wife share a bank account. Concurrently, the husband calls the withdraw() function and the wife calls deposit(). Describe how a race condition is possible and what might be done to prevent the race condition from occurring.

List three examples of deadlocks that are not related to a computer system environment.

What is paging? Consider a logical address space of 64 pages of 1,024 words each, mapped onto a physical memory of 32 frames.

i) How many bits are there in the logical address?

ii) How many bits are there in the physical address?

What is fragmentation? Consider the following segment table:

What are the physical addresses for the following logical addresses?

i) 0,430     ii) 1, 10     iii) 2, 500     iv) 3, 400

Explain why SSDs often use an FCFS disk-scheduling algorithm.

Explain the key differences between Batch Operating Systems, Multiprogramming Operating Systems, and Multitasking (Time-Sharing) Operating Systems. Specifically, describe how each system manages processes, CPU utilization, and user interaction. Provide examples of scenarios or use cases where each type of operating system would be most effective

Outline the lifecycle of a process, describing each state and the events that trigger transitions between these states.

What is process synchronization, and why is it important in an operating system? Describe common synchronization mechanisms (e.g., mutexes, semaphores) and explain how they prevent issues like race conditions.

Define the following term: i) Short-term scheduler ii) CPU dispatcher

Explain the difference between internal and external fragmentation.

Given memory partition of 100KB, 500KB, 200KB, 300K and 600KB (in order), how would each of the first fit, best fit and worst fit algorithms place processes of 212KB, 417KB,112KB and 426KB (in order)? Which algorithm makes the most efficient use of memory?

Briefly explain the purposes of system calls and system programs.

A hard disk with 4 platters that has 2048 tracks for each platter and 1024 sectors for each track and 512-byte sector. Calculate total capacity.

How does the distinction between kernel mode and user mode function as a rudimentary form of protection (security) system?

Consider the following set of processes, with the length of the CPU burst given in milliseconds:

The processes are assumed to have arrived in order P1, P2, P3, P4, P5 all at time 0.

i) Draw four Gantt charts that illustrate the execution of these processes using the following scheduling algorithms: preemptive priority (a large priority number implies a higher priority) and RR (quantum = 5)
ii) What is the turnaround time of each process for each of the scheduling algorithms
iii) What is the waiting time of each process for each of these scheduling algorithms?
iv) Which of the algorithms results in the minimum average waiting time (over all processes)?

Define a thread. How does it differ from a process in terms of resource management and execution?

How does thread scheduling differ from process scheduling? Explain with example.

Define internal and external fragmentation with necessary diagrams.

 Define page fault. What are the actions taken by the operating system when a page fault occurs, and how is this related to the TLB and page table?

A multithreaded web server wishes to keep track of the number of requests it services (known as hits). Consider the two following strategies to prevent a race condition on the variable hits.

Explain which of these two strategies is more efficient.

Explain the difference between internal and external fragmentation.