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Q1. Assume you have the following jobs to execute with one processor :

ProcessProcessing TimeArrival Time

Calculate the turnaround time, waiting time, average turnaround time, average waiting time, throughput and processor utilization for the above given set of processes that arrive at a given arrive time shown in the table, with the length of processing time given in milliseconds using FCFS, SJF, RR (with quantum 2) and SRTN scheduling algorithms. Also draw their corresponding Gantt charts.

Answer : - COMING SOON

Q2. Using C programming, write a semaphore based solution to Dining Philosopher’s problem and explain the program.

Answer : -

Q3. (a) Discuss how fragmentations manifest itself in each of the following types of virtual storage system.

Answer : -

i. Segmentation

ii. Paging

Paging is a memory management technique that permits the physical address space of a process to be non-contiguous.

iii. Combined segmentation and paging

Pure segmentation is not very popular and not being used in many of the operating systems. However, Segmentation can be combined with Paging to get the best features out of both the techniques.

In Segmented Paging, the main memory is divided into variable size segments which are further divided into fixed size pages.

Q3. (b) Compare direct file with indexed sequential file organization

Answer : -

Direct File Organization

Advantages of Direct File Organization

Disadvantages of Direct File Organization

Indexed Sequential File Organization

Advantages of Indexed sequential file organization

Disadvantages of Indexed sequential file organization

Q4. (a) Explain take-grant model for operating system security with an example. Also explain the mechanisms of security in WIN 2000 operating system ?

Answer : - The Take-Grant System is a model that helps in determining the protection rights (e.g., read or write) in a computer system. The Take-Grant system was introduced by Jones, Lipton, and Snyder to show that it is possible to decide on the safety of a computer system even when the number of subjects and objects are very large, or unbound. This can be accomplished in linear time based on the initial size of the system.

The take-grant system models a protection system which consists of a set of states and state transitions. A directed graph shows the connections between the nodes of this system. These nodes are representative of the subjects or objects of the model. The directed edges between the nodes represent the rights that one node has over the linked node.

There are a total of four such rules :


Q4. (b) Explain Bell and La-Padula Model for security and protection. Why is security a critical issue in a distributed OS environment ?

Answer : - The Bell-Lapadula Model of protection systems deals with the control of information flow. It is a linear non-discretionary model. This model of protection consists of the following components :

The set of access rights given to a subject are the following :

Control Attribute - This is an attribute given to the subject that creates an object. Due to this, the creator of an object can pass any of the above four access rights of that object to any subject. However, it cannot pass the control attribute itself. The creator of an object is also known as the controller of that object.

The following restrictions are imposed by the Bell-Lapadula Model :

Q5. Write and explain an algorithm used for ordering of events in a distributed environment. Implement the algorithm with an example and explain?

Answer : -

Q6. Discuss in detail the Process management, Memory management, I/O management, File management and Security and Protection for the following Operating Systems :


Answer : -

Process Management - A process is a program in execution. For example, when we write a program in C or C++ and compile it, the compiler creates binary code. The original code and binary code are both programs. When we actually run the binary code, it becomes a process.

A process will need certain resources — such as CPU time, memory, files, and I/O devices — to accomplish its task. These resources are allocated to the process either when it is created or while it is executing. Every process has an ID, a number that identifies it. A process may have more than one thread. A thread is an object that identifies which part of the program is running. Each thread also has an ID (a number that identifies it).

The purpose of a thread is to allocate processor time. On a machine with one processor, more than one thread can be allocated, but only one thread can run at a time. Each thread only runs a short time and then the execution is passed on to the next thread, giving the user the illusion that more than one thing is happening at once. On a machine with more than one processor, true multi-threading can take place. If an application has multiple threads, the threads can run simultaneously on different processors.

b) ANDROID Version 9.0 (PIE)

Answer : - COMING SOON

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