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Questions tagged [operating-systems]

Questions about the principles of software that interfaces between hardware and applications.

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Why does paging not have external fragmentation?

I have read that paging does not suffer from external fragmentation as the frames and the pages are all of the equal sizes, but when we store a last level page table in a frame at that time it may not ...
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1answer
41 views

How does dynamic memory-allocation exactly work?

I have wondered about profane code. Assume we are running this code on any modern System like Unix/Linux/Mac/Windows. This code is C, but it should work with every language which is close to the ...
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Differences between linux and windows [closed]

What are some major differences between two kernels? In terms of performance and code elegancy?
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82 views

How to calculate average waiting time for round robin cpu scheduling?

I have tried to calculate average waiting time for the below details there are two answers I'm getting using two methods I'm not understanding which one is correct? The time quantum is 2 This is the ...
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4answers
7k views

Why do we need the valid-invalid bit in a page table?

I'm reading about memory management in Operating System Concepts, by A. Silberschatz. The author says: [...] the user process by definition is unable to access memory it does not own. It has no ...
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0answers
5 views

Why does running GHCi in Windows make it not possible to detect infinite loops? [migrated]

I'm currently reading "Haskell Programming from first principles" and there is a paragraph in the section about bottom that reads: Let us examine a few ways by which we can have bottom in our ...
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0answers
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CMD, Command line prompt in Windows. Delete all files in a specific folder except certain extensions and files with specific names [migrated]

I apologize if I tagged this question wrong. I have started using cmd literally yesterday so, forgive me if the question is too easy. Any help is appreciated. I need to delete 20,000+ files with 10+ ...
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2answers
2k 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 ...
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0answers
13 views

Why in the Map Reduce Implementation, why not stream the records to the reducer (via TCP) as they are being produced by the mappers?

In the Map-Reduce implementation, the reducers start when all mappers finish their jobs. Why don't we stream the records from mappers to reducers while they are being processed instead? I think there ...
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1answer
431 views

Convoy effect in priority scheduling and SJF (Non preemptive)

In books, I have read that FCFS suffers from convoy effect. I think that even SJF and priority(both preemptive and non preemptive) can suffer from convoy effect. In SJF, if a process with large burst ...
4
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1answer
77 views

Task scheduling algorithm that limits concurrency

My prof introduced us an algorithm with semaphores that was used to solve the "dining philosophers" problem. The algo is ok, apart from that it limits concurrency. What does mean that it "limits ...
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2answers
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What type of operations are seen the most at the physical disk level — reads or writes? Why?

This question came up in my operating systems class in a section about file system cache and RAID. I'm speculating that the answer is that writes are seen more at the physical disk level because an ...
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6answers
2k views

How can a CPU access more memory locations than 2^wordsize?

I noticed that CPU's like the 8086 and especially the 8080 have the ability to access more memory than what one would normally assume. The 8080, for example, has an 8-bit word size but can use a 16-...
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0answers
28 views

Any good source explaining multiprocessor synchronization techniques and their implementation

I need to study how synchronization is done in a multiprocessor operating system, but I am unable to find a good source. I have read about it in the book "Modern Operating System" by Tanenbaum, but I ...
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2answers
93 views

Why operating system needs interrupt stack, if it has process control block?

I'm reading about an operating system but some concept confuses me. What doesn't confuse me: When an interrupt or system call or processor exception occurs, it happens when user mode tries to ...
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1answer
117 views

How can i draw a general resource graph which cannot be completely reduced but which is free from deadlock?

How can i draw a general resource graph which cannot be completely reduced but which is free from deadlock? A general resource graph which can be completely reduced and hence is free from deadlock is ...
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0answers
16 views

Inputting values to register files

I'm trying to understand how to register files. The question below is from past exam paper: The following diagram shows the register-file from a simple 8-bit machine I don't fully get register ...
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1answer
21 views

What architectural features will allow this microprocessor to access a separate “I/O space”?

I'm studying for my final and don't understand this question. Here is the full question (from Stallings 8th edition): Consider a hypothetical microprocessor generating a 16-bit address (e.g., ...
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1answer
34 views

How exactly does a CPU do process scheduling?

I know in theory how various scheduling algorithms work, such as round robin, where each process is given small time slices to run a few instructions, before the operating system passes execution onto ...
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1answer
2k views

Operating Systems - SJN/Round Robin - turn around time + waiting time

2.(10 pts) a) You are given 4 processes in a batch system that all arrive at time 0 with the following CPU burst times: P1 : 35, P2: 25, P3: 13, P4: 22. Assuming there is no context switch ...
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0answers
33 views

How can an unstable kernel write a memory dump?

I always wondered how a kernel that became unstable, e.g. due to a BSOD or a kernel panic, is able to do specific tasks. For example, if a Windows driver corrupts the stack of the kernel. It leads to ...
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1answer
115 views

Why do OS and DBMS have their own synchronisation mechanisms, when OS can alone do it and it sits at the bottom of DB?

I know that synchronization is important in the OS, but why do we need a separate topic synchronization and concurrency in the DBMS? The OS concentrates on program synchronization while the DBMS ...
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1answer
43 views

EDF vs Rate Monotonic context changes

I'm studying real time scheduling algorithms. In particular EDF and Rate monotonic. I have an intuition that using EDF we have less context changes than using Rate Monotonic. But i dont know how to ...
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1answer
59 views

Explain in laymen terms - How do modern programs translate into machine code

I'm sure this will benefit anyone else on a computer science fundamentals back-fill journey.. I'm slowly learning Assembly and while I'm starting to understand the core of it (MOV, JUMP, etc) and can ...
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1answer
86 views

Single processor system supporting two running processes, A and B, with the following sequential execution patterns [closed]

Can anyone please help me with the following question? Consider a single processor system supporting two running processes, A and B, with the following sequential execution patterns: A: [CPU 8 ms; ...
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0answers
447 views

Latency and Throughput Bounds

Say that I have a superscalar processor and I am given the latency, issue and capacity (in clock cycles) for different instructions. What is the general formula for latency bound and throughput bound?...
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0answers
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Understanding Bounded Waiting

I am trying to understand bounded waiting and i have a question. The definition is as follows: Bounded waiting - There exists a bound, or limit, on the number of times that other processes are ...
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1answer
28 views

what is the difference between Operating system and Window Systems?

Quoting from Tannenbaum_Operating_Systems_Design : On top of the operating system is the rest of the system software. Here we find the command interpreter (shell), window systems, compilers, ...
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1answer
714 views

Deadlock and safe state

I read that system being in safe state doesn't guarantee that deadlock is not possible. Can someone give me an example where system is in safe state and deadlock is possible?
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1answer
54 views
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1answer
19 views

Memory Mapping Segment

I read that "Memory Mapping Segment"/"memory mapped file" is a segment of the virtual memory of a process, where a file or file-like Ressource is loaded into. It is for high performance file I/O. I ...
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1answer
23 views

How the operating system allocated to dual-channels memory?

I learned that the boot loader transmit the operating system from Hard Disk to Main Memory during the booting process. I wonder, today's computers are equipped with multiple slice of memory of dual-...
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1answer
5k views

How does the OS determine the CPU burst time of a process?

This question is related to OS. After having solved many problems in CPU scheduling I was wondering how does the CPU know the burst time of all the processes in the main memory before executing them? ...
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4answers
2k views

Operating System - CPU scheduling Decisions

I understand that CPU scheduling takes place on 4 circumstances listed below: When the process changes state from Running to Ready Changes state from Running to Waiting Changes state from Waiting to ...
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3answers
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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 ...
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1answer
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What does 'buffering' mean?

I read the lecture 4 of CS162 (UC Berkeley: https://inst.eecs.berkeley.edu/~cs162/sp17/static/lectures/4.pdf), but I got little bit confused about the meaning of the keyword "buffered" they used when ...
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0answers
233 views

LRU vs FIFO page replacement

I am wondering if there is an instance where FIFO results in less page faults than LRU. For example: 2,6,5,7... In this string, if I have to complete it by ...
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0answers
21 views

Addresses with no memory allocated

I've read that a program can crash if it tries to access addresses with no memory allocated. But, how is it possible that an address has no memory allocated? When does it happen?
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1answer
2k views

User level threads are transparent to the kernel?

Find whether given statement True or False? Explain. User level threads are transparent to the kernel? My attempt : False. Since, user level threads are managed by a user level library however, ...
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0answers
49 views

Difference between present - absent bit and valid - invalid bit in a page table?

while reading I found this: Present/Absent bit – Present or absent bit says whether a particular page you are looking for is present or absent. In case if it is not present, that is called Page ...
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1answer
61 views

Appreciation of the 5 state process model

I'm starting out in an Operating Systems module. I have a few understanding questions to think about, which will not be gone through in class. A process state model is an abstraction (or model) which ...
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153 views

Two Process Solution for Critical Section Problem- Algorithm 1

I have started learning Critical Section Problem and its various solutions. To explain my question, let me first give a brief background of it. The general structure for a two Process Solution for ...
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1answer
16 views

address spaces of changing processes

I read that the mapping for user-space processes is changed after each process switch. By mapping I mean the translation from virtual addresses to "real" memory address. I thought that processes are ...
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1answer
33 views

What does it mean " The outer level page table need not be page aligned?

The question is in context to multilevel page table. I was trying to solve numerical on multi-level paging and noticed that page size might not be same at all levels. I came across the point "Outer ...
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0answers
264 views

Difference between Response time, Execution time, and CPU time

I studied Computer Architecture from David A. Patterson and have came across the idea of Response time. Response time also called Execution time. The total time required for the computer to ...
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4answers
35k views

What threads share in general?

Well this is general question. And if anyone want to make it implementation specific then I will prefer Unix related stuff. But first need to know following problems in generality: I read single ...
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1answer
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Why is there no one to many Multithreading Model?

I am studying various multi-threading models. Here the user threads are mapped to Kernel Threads. They are - ...
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1answer
14 views

multithreading - duration of jobs

" How long will it take for 2 jobs to complete if they're running in parallel, knowing that both have a total of 20 minutes of CPU usage time and 50% IO" I calculated the CPU usage: ...
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0answers
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Calculate for each block, the number of bytes that can be assigned to data and to pointers to other blocks

In trying to solve the following problem: You are presented with the first 15 blocks of a secondary storage device (disk) which has a total of 30000 KB available. The linked allocation method is ...