Questions about the principles of software that interfaces between hardware and applications.
2
votes
4answers
52 views
Cross platform apps and programing languages…how is it done?
I always wondered how various certain languages like Java, HTML5 and browser extensions are made with cross platform(operates and functions the same, regardless of OS, being Linux/Windows/BSD not ...
1
vote
1answer
31 views
Hierarchical Paging
Suppose I have a system with 32-bit logical and 16-bit physical address spaces, and the page size is 512 bytes. For simplicity, ignore the valid/invalid bits in the page table.
How many sections will ...
0
votes
1answer
38 views
General question about how CPUs send and receive data/bytes to hardware?
Realize I didn't mention x86 or any more details to make this non-specific to any platform, but to just get a general idea of how this is done(this is also a long question with a lot of details).
I ...
0
votes
1answer
35 views
Must a deadlock necessarily occur if the four conditions exist?
I understand the four necessary conditions, mutual exclusion, hold and wait, no preemption, and circular wait, for deadlock to occur. However, does there exist a situation where the four conditions ...
1
vote
0answers
29 views
The relation between privileged instructions, traps and system calls [migrated]
I am trying to understand how a virtual machine monitor (VMM) virtualizes the CPU.
My understanding right now is that the CPU issues a protection fault interrupt when a privileged instruction is ...
1
vote
1answer
120 views
How to calculate the size of page table
Assuming pages of 4Kbytes and 32-bit addressing, estimate the maximum size of the page table for each process.
I think this is $2^{32}$?
Is there a formula for this?
1
vote
1answer
47 views
How does a program execute with respect to the operating system?
I am reading Operating Systems by William Stallings 6th edition and I came across this text,
Program execution:
...
-2
votes
1answer
50 views
Calculating wasted space [closed]
How would wasted space be calculated?
Six equally sized data blocks, each containing 209 bytes, are to be recorded on to hard disk. Each sector on the hard disk has 512 bytes storage capacity. With ...
0
votes
0answers
31 views
Relinquishing criteria for operating systems
What is meant by relinquishing criteria for a scheduling algorithm such as First in fist out? I know this algorithm choses the first process to be executed by the scheduler. Is it non pre-emptive ...
0
votes
2answers
87 views
Disk scheduling and process scheduling
Whats the diffrence between Disk scheduling and process scheduling? I mean i know the roles of disks and processes, but it seems to me they both have the same aim. to reduce monopolies, they even both ...
0
votes
1answer
119 views
How to compute the effective access time in Virtual Memory system with demand paging?
Given the following exercise from Operating System Concepts Essentials 1st Edition, Chapter 8 Virtual Memory:
An operating system supports a paged virtual memory, using a central
processor with ...
0
votes
0answers
37 views
Overlapping and non-overlapping systems
what are overlapping and non-overlapping systems in relation to uni-processor and multi-processor? I understand uni-processor is a system with one CPU, and multi-processor has two or more CPU's.
The ...
1
vote
2answers
77 views
Given the logical address, how to extract the page number?
I am studying Computer Systems. I have th following question and its answer:
Given the logical address 0xAEF9 (in hexadecimal) with a page size of
256 bytes, what is the page number?
...
0
votes
1answer
63 views
concurrency and hardware
I've a couple of questions that I need answers for. What I am looking for here is the outline of the answers. Not necessarily the exact complete answer. I can do that.
The question is that common ...
0
votes
1answer
422 views
Internal and External Fragmentation
I am working over a homework problem and am confused on how to determine whether there is internal and external fragmentation given the following table:
...
0
votes
1answer
142 views
The convoy effect in process scheduling
As I understand the convoy effect, in the context of vehicular traffic in a road system. A slow moving group of vehicles passes through the system, slowing traffic even in areas which were not ...
1
vote
1answer
33 views
Hardware interrupts from keystrokes
If there is an interrupt from every keypress (or one for keydown, one for keyup, one for keypress?) how does the OS handle so many interrupts at the same time. A person typing at 120WPM would be ...
1
vote
1answer
79 views
Changing from Kernel mode to User mode (and vice versa)
I am reading Operating Systems book by Galvin. Galvin explains, what are kernel & user modes, instruction privileges given for both modes & also about mode-bit. But I am interested to know how ...
3
votes
1answer
88 views
Look Ahead buffer vs Translation Look aside buffer
I know that Translation look aside buffer is used for address translation in paging to achieve better performance.
I came across term called Look Ahead buffer in a document which said it implements ...
1
vote
1answer
132 views
clarification about Algorithm of page replacement LRU with reference bits
Studying LRU approximation Algorithms I think to have not understand how it works, for example:
...
1
vote
2answers
63 views
What mechanisms prevent a process from taking over the processor forever?
Suppose a process keeps running code (e.g. an infinite loop). How can other programs take over? What prevents the process from remaining active forever?
3
votes
2answers
45 views
Dangerous interrupts
Let's say we have a fictional operating system in the user mode. Whenever an interrupt or a trap occurs, the os would switch to the Kernel mode jumping to the address determined from the interrupt ...
0
votes
1answer
32 views
How Does Dynamic Heap Storage Have Something to Do with Heap?
There are three typical ways to allocate memory for programs: static, stack and dynamic heap. However, when I look at the implementation of dynamic heap memory allocation from wikipedia , what I found ...
0
votes
1answer
469 views
How to work out physical address corresponding to logical address?
I am looking to calculate the physical address corresponding to a logical address in a paging memory management scheme. I just want to make sure I am getting the calculation right, as I fear I could ...
2
votes
1answer
175 views
SSTF disk scheduling algorithm? What if lowest seek times are equal in either direction?
Using the Shortest-Seek-Time-First (SSTF) disk scheduling algorithm (where we select a request with a minimum seek time from the current head position), what happens if the requests in both directions ...
0
votes
3answers
122 views
Which would provide a stronger base for future learning? C vs C++ [closed]
I've studied C++ for about a year now independently, having an initial goal of the usual "i want to program video games" to a new found goal of pursuing computer science as a full time career. ...
1
vote
2answers
717 views
Calculation of effective average instruction execution time in a 2-level paging system
System has a two level paging scheme
Average CPU time for a instruction = 100ns
Average number of memory accesses per instruction = 2
Regular memory access = 150 ns
Page fault service ...
2
votes
1answer
75 views
Processes and Segmentation
The following problem was on my final and in Gate 2006, but I don't understand how to solve it:
Different methods of memory management have different overheads:
...
1
vote
2answers
351 views
How does increasing the page size affect the number of page faults?
If we let the physical memory size remain constant,
What effect does the size of the page have on the number of frames?
What effect does the number of frames have on the number of page faults?
...
1
vote
1answer
67 views
Process state in multi threaded process
What would be the process state in a multi threaded process, in which threads are in different states (running, waiting, blocked etc)
1
vote
1answer
203 views
Scheduling algorithms and quantum time
I would like to know what impacts does a scheduling algorithm say Round Robin of FIFO have on a Operating system. I understand the a scheduling algorithm has the processes run in burst then switch ...
-1
votes
1answer
76 views
Why have two functions, exec and execv? [closed]
What is the use of having two exec functions like execv and exec? what I mean is why would ...
3
votes
1answer
145 views
Program compilation and execution flow
I was studying operating system concepts from Silberschatz, Galvin and Gagne's book (sixth edition) and I have some questions about the flow of execution of a program. A figure explains the processing ...
4
votes
1answer
492 views
First-Come-First-Serve scheduling algorithm - what happens to process after returning from I/O? where does it go in the queue
There are three processes in line
P0, P1, P2
1) P0 registered and executes
2) P0 I/O blocked
3) so P1 executes
4) P1 I/O blocked
5) P0 executes. ??
After P1 must come P2 that is what FCFS ...
3
votes
1answer
110 views
What is the difference between a module in a monolithic kernel and a server in a microkernel?
I´m not exactly sure what kind of impact these two things have on kernel design. Are servers more flexible because of running in user space, for instance, and does adding a module require a new build ...
1
vote
0answers
89 views
Object-based distributed Operating systems [closed]
Can any one explain how object-based technology used in distributed operating systems?
Also can any one suggest any learning resources (links, slideshows, e-books etc) to learn about Amoeba OS?
3
votes
2answers
180 views
What if the electricity goes off while a file is being renamed?
Suppose I'm renaming a file and the electricity goes off right in the middle. Naively, it looks like the file could be in some “half-renamed” state. Maybe the name would have half the old name and ...
5
votes
4answers
868 views
Is the 2nd parity bit in RAID 6 a simple calculation?
I'm trying to understand how the 2nd parity bit or byte is set in RAID 6. I'm reading a paper by H. Peter Anvin, and it goes into Galois field algebra, which is somewhat new to me. Anyway, a rep from ...
2
votes
0answers
502 views
How does worst-fit memory allocation react when encountering contiguous empty memory blocks?
So I have a problem understanding how the worst-fit protocol for memory allocation reacts to contiguous blocks of empty memory. None of the examples I have found address this possibility.
For ...
6
votes
1answer
110 views
Variation of the dining philosophers: is the standard solution still valid?
I have a problem that is almost equal to the standard one of the dining philosophers, but has a quirk: while a philosopher thinks, he still holds the fork on his left.
If after the period of thinking ...
4
votes
1answer
250 views
How are threads implemented in different OSs?
I was reading Linux Kernel Development by Robert Love, where I came across this
Linux takes an interesting approach to thread support: It does not
differentiate between threads and normal ...
2
votes
1answer
148 views
Massalin's Synthesis Quajects equivalent to ASM generating macros used in Game Oriented Assembly LISP?
Alexia Massalin's Dissertation on Synthesis was a Phd thesis on Operating Systems that contained a concept called 'Quajects' (see Chapter 4).
This is some additional commentary on the Phd Thesis.
...
7
votes
1answer
1k views
Swap space management during pure demand paging
The following is a doubt that I came across while doing a OS home assignment - however, it seems more concept-based than a straightforward coding question, so IMHO I don't think the homework tag is ...
4
votes
1answer
105 views
What techniques exist for energy-efficient computing and networking?
I am currently reviewing the potentials of cloud computing regarding energy efficiency and green IT. In connection with this review I am having a look on techniques for increasing energy-efficiency in ...
6
votes
4answers
730 views
What is meant by interrupts in the context of operating systems?
I've decided to read Operating Systems Concepts by Silberschatz, Galvin Gagne (8th edition) over the summer. I've gotten to a topic that's confusing me - interrupts and their role as it relates to ...
4
votes
1answer
103 views
Requirements for emulation
What are the complete specifications that must be documented in order to ensure the correct execution of a particular program written in Java? For instance, if one were archiving a program for ...
6
votes
1answer
779 views
How to interpret “Windows - Virtual Memory minimum too low” from a CS student point of view?
On my old 256MB RAM, pc I get this message. (I guess it is quite common)
Windows - Virtual Memory minimum too low
Your system is low on virtual memory. Windows is increasing the size of your ...
10
votes
6answers
320 views
What are examples of inconsistency and incompleteness in Unix/C?
In Richard Gabriel's famous essay The Rise of Worse is Better, he contrasts caricatured versions of the MIT/Stanford (Lisp) and New Jersey (C/Unix) design philosophies along the axes of simplicity, ...
4
votes
1answer
3k views
What is the average turnaround time?
For the following jobs:
The average wait time would be using a FCFS algorithm:
(6-6)+(7-2)+(11-5)+(17-5)+(14-1) -> 0+5+6+10+13 -> 34/5 = 7 (6.8)
What would the average turnaround time be?
4
votes
1answer
697 views
Which queue does the long-term scheduler maintain?
There are different queues of processes (in an operating system):
Job Queue: Each new process goes into the job queue. Processes in the job queue reside on mass storage and await the allocation of ...
