XML CO527 Anonymous Questions and Answers

This page lists the various questions and answers. To submit a question, use the anonymous questions page. You may find the keyword index and/or top-level index useful for locating past questions and answers.

We have taken the liberty of making some minor typographical corrections to some of the questions as originally put. Although most of the questions here will have been submitted anonymously, this page also serves to answer some questions of general interest to those on the course.

Question 241:

Submission reference: IN1237

Will we need to know about all of the memory management strategies or is it sufficient to concentrate mainly on Not Used Recently ?

Answer 241:

As you say, concentrate mainly on the NUR strategy, as this was the one covered in depth in the lectures. You should at least be aware of the others, however, but would not be expected to know in detail how they operate (except maybe FIFO and random, which are obvious).

Question 242:

Submission reference: IN1238

Can you for the following questions and answers tell me if I am missing something in my answer which would reward me full marks, thanks:

Q: why is IPC needed?
A: IPC is needed for mutual exclusion, syncronisation and cooperation and communication. (here i'd go into what each of those are)

Q: what's a device driver?
A: Because devices can have different, and sometimes incompatible characteristics, they need a driver which interfaces them to the O.S. They have to provide a unified interface to the system. They are implemented in the software and need to hide device differences such as speed of transfer, unit of transfer and shareability.

Q: what's spooling?
A: Spooling makes slow unshareable devices shareable. Processes that need to use the device place a file in the queue and let the spooler process know about it. Usually the queue follows a FIFO system.

Q: how is an executable produced?
A: the source code is prepared, the source files compiled to object modules and the modules linked to libraries to produce the executable

Q: how is a program loaded?
A the resource requirements are determined, memory areas are allocated, different areas of the virtual machine are read in, the program is linked to the system libraries

Gracias!

Answer 242:

I cannot tell you to what extent full marks would be obtained without having the marking scheme..! (and maybe a set of relevant learning outcomes). But I'm happy to provide some feedback:

Regarding the need for IPC, mutual-exclusion and synchronisation are examples of cooperation and communication, so you don't need to mention them explicitly like this. For such a short question I would probably not expect any significant detail in the answer.

Regarding device-drivers, yes, that's a good answer.

Your answer to the spooling questions assumes slow devices, but this is not necessarily the case. You describe one type of spooling (non-transparent) but not the other (transparent). For an exam question such as this I would probably only expect a description of one. As we say, use the number of marks as a guide for how much time to spend on each question (in turn, how much to write).

In your answer to producing executables, I would query the phrase "linked to libraries". "linked with libraries" is technically more accurate. "linked to libraries" implies some modification of the libraries with the object code, which is not the case. A better approach would be to rephrase the answer completely, e.g. "... and then a linker is used to combine the object modules and libraries to produce an executable".

For your last question, the answer is mostly fine, but I would query the last part. Linking at load-time only occurs where it is needed. If the link-editor has resolved all external references, there won't be any need for load-time linking (by a link-loader).

Keywords: exams

Question 243:

Submission reference: IN1239

Are these 3 types of Operating Systems?

Client server, layered and micro-kernel

merci!

Answer 243:

Going on the material lectured this year, you would probably only get marks for "micro-kernel". Typical properties of a micro-kernel system are that it is client-server and that it is layered. See the handout of lecture 1 for a possible set of correct answers.

Keywords: exams

Question 244:

Submission reference: IN1240

Where is the page table kept?

Answer 244:

See lecture 6 slide 6 — in physical memory usually, though they can themselves be paged.

Keywords: memory-management

Question 245:

Submission reference: IN1241

for the speed up factor, if you have a processor of 1 ghz and 10 stages, to calculate the time of each stage do you divide 1/1ghz?

Answer 245:

Yes, see Question 204 (2006).

Keywords: architecture

Question 246:

Submission reference: IN1242

When evicting the page frames in the NUR strategy. If pages 0 and 4 both aren't referenced or modified, which one will be evicted first? Thanks

Answer 246:

This refers to a question on the 2007 CO527 paper.

It doesn't matter — either order is ok.

Keywords: memory-management , exam

Question 247:

Submission reference: IN1268

I have just done an exam and all questions must be answered correctly. the last question I answered part correct and part of the question completely wrong! How would this be marked?

Answer 247:

Is this relevant to CO527..? (that exam was some time ago). However, if you answer part of question wrongly, don't expect to get many marks for it! The only exception would be if the question was worded in such a way that it could have been misinterpreted (and your answer follows this misinterpretation).