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Old 17-07-2010
piyush123
 
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Operating Systems concepts?

I'm teaching myself from what I find online, I found a few questions that I was hoping someone could help me answer.

1. Memory allocation and garbage collection are appropriate topics in both a programming languages course and an operating systems course. What makes them particularly relevant to an operating systems course like this one?

2. Should memory be assigned in contiguous blocks or not? Does the existence/use of virtual memory make any difference?

3. The number of address bits in a machine instruction is related to the amount of memory that can be addressed. Explain.

4. Disks can be used to store files, spool input and output, and keep virtual memory, and potentially other things. The disk scheduling algorithms discussed in the textbook seem to be oriented to just one of these uses. How could you build on or improve that?

5. Why does disk arm movement scheduling play such an important role in disk scheduling?

6. What does it mean for a file system to be journaled?
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Old 20-04-2011
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Join Date: Nov 2009
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Re: Operating Systems concepts?

1. Memory allocation and garbage collection are appropriate topics in both a programming languages course and an operating systems course. What makes them particularly relevant to an operating systems course like this one?

The major work on an OS is to manage the memory need of the computer. So if you are using a multi user system then this becomes an important part. Most of the user are using computer at the same time and also consumes that amount of memory. As a simple example think that there are around 6 to 7 people using a same table for paper work. So the first user when come next days does not found on his work due to heaps of paper. Here the Table is the Desktop and this is the thing which an operating system manages. This is were your question is answered.

2. Should memory be assigned in contiguous blocks or not? Does the existence/use of virtual memory make any difference?

Virtual memory plays a vital role in initiation your operating system performance. Here how it works. The data is processed by cpu and then stores in cpu cache which is then managed by ram and then for later use kept in the virtual ram. Imagine if there is no virtual ram and continuous blocks to ram would led to your system freeze. This relatively important for those who works mostly on data transfer services.

3. The number of address bits in a machine instruction is related to the amount of memory that can be addressed. Explain.

In an system the memory address is an kind of an identifier for memory location. This is the place where the a computer application or a hardware keeps the data and then receive the same back. This is in a form of binary number which is describe by the ram itself. Now in modem system which are mostly byte-addressable computers every address recognize the single byte of storage. If data ha a big size then those single byte are replaced by multiple and in this way they keep occupying the space. The absolute address in a system is actually the memory address which looks for the location inside a ram. This the way by which the performance is counted on the basis of ram size.

4. Disks can be used to store files, spool input and output, and keep virtual memory, and potentially other things. The disk scheduling algorithms discussed in the textbook seem to be oriented to just one of these uses. How could you build on or improve that?

That is correct to most extent. The empty space in the disk is nothing but a kind of space which can be transferred to virtual ram or page file. You know one thing the ram comes with size like 1GB, 2GB, 4GB, etc. So the system has that much of dedicated space to hold the processed data. And then the data for future use is posted on the virtual ram which is wiped on boot. Sometime larger disk space helps yout to initiate the speed of an operating system.

5. Why does disk arm movement scheduling play such an important role in disk scheduling?

Now there are number of algorithms for this. I will discuss on Elevator Algorithm for this. Here is an basic information how disc scheduling works. There are four processes in that. The first one is it checks that whether there is an input or output. Second the disk address for the transfer, third process is memory address for transfer and the last is number of bytes to be transferred. Here you can get a basic overview of working. In Elevator the first request is firstly served. There other more which can put highlight on the same like Anticipatory scheduling, CFQ, Deadline scheduler, # FIFO, FSCAN, I/O scheduling, LOOK algorithm, N-Step-SCAN, Noop scheduler and Shortest seek first.

6. What does it mean for a file system to be journaled?

Journaling a file system means that the file system on the drive has s record of whatever changes are make in the journal. There is an kind of log which is situated in a dedicated part of file system. This is saved before doing any changes to the main file system. The best part of journaling a file system is that when your system crashes or corrupted then it is becomes much faster and easier to bring the system back online.
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