BT0070 - Operating Systems

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ASSIGNMENT

PROGRAM	BSc IT
SEMESTER	SECOND
SUBJECT CODE & NAME	BT0070, Operating Systems
CREDIT	4
BK ID	B0954
MAX.MARKS	60

Q. No.1 List the approaches to design operating system structures. Explain any two of them. 2+8=10

Answer:

Listing of approaches to design operating system structures:

Ø  Layered approach

Ø  The kernel based approach

Ø  The virtual machine approach

Ø  Layered approach

Ø  Dijkstra suggested the layered approach to lessen the design and implementation complexities of an operating system. The layered

2 Write short notes on:

1. Process Creation

2. Terminating Process 5+5= 10

Answer:

1.       Process Creation

During the course of execution, a process may create several new proceses using a create-process system call. The creating process is called a parent process and the new processes are called the children of that process. Each of these new processes may in turn create other processes, forming a tree of processes.

Process Termination

A process terminates when it finishes executing its last statement and asks the operating system to delete it by using the exit system call. At that time, the process should return the data (output) ti its parent process via the wait system call. All the resources of the process, including physical and virtual memory, open files, and I/O buffers, are deallocated by the operating system.

Only a parent process can cause

3 Is it possible to check the condition of mutual exclusion through hardware assistance? If yes, how? 10

Answer: Checking for mutual exclusion is also possible through hardware. Special instructions called Test and Set Lock (TSL) is used for the purpose. An important feature is that the set of instructions used for this purpose is indivisible, that is, they cannot be interrupted during execution. The instruction has the format TSL ACC, IND where ACC is an accumulator register and IND is a memory location used as a flag. Whenever the instruction is

Q4

1. Given a total of 5 units of resource type 1 and 4 units of resource type 2, tell whether the following system is in a safe or unsafe state. Show your work. Type 1 Type 2 Process Used Max Used Max P1             1      2      1        3 P2             1      3      1         2 P3             2      4      1         4

5. What is the concept of virtual memory? Why virtual memory is needed? 3+7= 10

Answer: Virtual memory is a technique that allows execution of processes that may not be entirely in memory. In addition, virtual memory allows mapping of a large virtual address space onto a smaller physical memory. It also raises the degree of multi-programming and increases CPU utilization. Because of the above features, users are freed from worrying about memory requirements and availability.

Need for Virtual Memory Technique

Every process needs to be loaded into

6 What do you mean by Global OS? State the concept of migration and resource allocation in Global OS.

4+6= 10

Answer: Global Operating System (GOS)

The NOS is responsible for activities such as memory and process management on the server. The NOS converts a request into a task, schedules and executes it. Memory and processing power in all other computers in the network is not tapped to the maximum by a NOS. This is exactly what the GOS attempts to do. It has a list of processes executing on different machines and the resources needed by each one of them. Relatively free

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