MCA2010 – OPERATING SYSTEM

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(SUMMER 2015,  ASSIGNMENT)

PROGRAM	MCA(REVISED FALL 2012)
SEMESTER	2
SUBJECT CODE & NAME	MCA2010 – OPERATING SYSTEM
CREDIT	4
BK ID	B1405
MAX.MARKS	60

Note: Answer all questions. Kindly note that answers for 10 marks questions should be approximately of 400 words. Each question is followed by evaluation scheme.

1 What is operating system? Explain any four major functions of operating system.

Answer: The operating system is the most important program that is on a computer.  The operating system basically runs the computer and allows other programs to run as well.  The operating system does all the basic things that a computer needs to do, such as recognizing inputs from the mouse or the keyboard.  It keeps track of where all the files are on the computer.  It allocates resources to the various programs that are running and it prevents unauthorized access to the computer.

The most popular operating system today is Microsoft's Windows operating system.  Macintosh computers have their own operating system, the

2 Explain the different process states.

Answer : A process is a program in execution. The execution of a process must progress in a sequential fashion. Definition of process is following.

A process which is Executed by the Process have various States, the State of the Process is also called as the Status of the process, The Status includes whether the Process has Executed or Whether the process is Waiting for Some input and output from the user and whether the Process is Waiting for the CPU to Run the Program after the Completion of the Process.

The various States of the Process are as Followings:-

3 Define Deadlock. Explain necessary conditions for deadlock.

Answer : A deadlock is a situation in which two computer programs sharing the same resource are effectively preventing each other from accessing the resource, resulting in both programs ceasing to function. The earliest computer operating systems ran only one program at a time. Eventually some operating systems offered dynamic allocation of resources. Programs could request further allocations of resources after they had begun running. This led to the problem of the deadlock.

 Coffman (1971) identified four (4) conditions that must hold simultaneously for there to be a deadlock.

4. Differentiate between Sequential access and direct access methods.

Answer : The hypertext and hyperlink exemplify the direct-access paradigm and are a significant improvement over the more traditional, book-based model of sequential access.

(Direct access can also be called random access, because it allows equally easy and fast access to any randomly selected destination. Somewhat like traveling by a Star Trek transporter instead of driving along the freeway and passing the exits one at a time, which is what you get with sequential access.)

In a normal, physical book, the reader is supposed to read pages one by one, in the order in which they are provided by the author. For most books (fiction, at least), it makes little sense for the reader to turn directly page 256 and start reading there.

5. Differentiate between Daisy chain bus arbitration and Priority encoded bus arbitration.

Answer : In most mini- and mainframe computer systems, a great deal of input and output occurs between the disk system and the processor. It would be very inefficient to perform these operations directly through the processor; it is much more efficient if such devices, which can transfer data at a very high rate, place the data directly into the memory, or take the data directly from the processor without direct intervention from the processor. I/O performed in this way is usually called direct memory access, or DMA. The controller for a device employing DMA must have the capability of generating address signals for the memory, as well as all of the memory control signals. The processor informs the DMA controller that data is

6. Explain LRU page replacement algorithm with example

Answer: A good approximation to the optimal algorithm is based on the observation that pages that have been heavily used in the last few instructions will probably be heavily used again in the next few. Conversely, pages that have not been used for ages will probably remain unused for a long time. This idea suggests a realizable algorithm: when a page fault occurs, throw out the page that has been unused for the longest time. This strategy is called LRU (Least Recently Used) paging.

Although LRU is theoretically realizable, it is not cheap

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