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Questions tagged [operating-systems]

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

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How does paging avoid external fragmentation with different page sizes across processes?

It's commonly said that paging has no external fragmentation, only internal fragmentation. But I've read that some architectures have support for different page sizes. And different processes can use ...
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Regarding Logical Addressing in Segmented Paging Architecture

We know that segments can be divided into pages and it has its own page table ..... Likewise paging can be incorporated into the segment table and it'll be associated with its own page tables ...... ...
Achyutananda Sahoo's user avatar
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How do threads aid in execution of a program?

Firstly this is not a question about programming. A book I am reading on C programming explains briefly the steps of execution of a C program after its compilation. It states the following, To be ...
Quorthon's user avatar
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Why is the default page/block size 4 KiB?

Clearly, some empirical study on an older machine helped us choose a 4KiB page size to balance TLB hit rate and fragmentation. Modern hardware and operating systems support this size for backward ...
idle_cycles's user avatar
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Which is not the benefit of DLL

Which of the following is NOT an advantage of using shared, dynamically linked libraries as opposed to using statically linked libraries? (a) Smaller sizes of executable (b) Lesser overall page fault ...
Swastik Sanyal's user avatar
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A program detecting whether it's running in a virtual machine

I heard hypervisors try to make this undetectable to the client .A good hypervisor will have zero latency and be transparent. Can a program detect whether it's running in a virtual machine by trying ...
Jess Fuckett's user avatar
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What could cause a Windows 11 machine to have so much more elapsed time relative to a Windows 10 machine?

I have a Windows 10 desktop (6 years old - Dell Optiplex) and a new Windows 11 laptop (maybe last years model - Lenovo Thinkpad P16 Gen2). I am running scripts in R to compare their compute times. The ...
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Size of page Table entry

The following question was asked by our professor in exam:- Given a system with 4GB virtual address space and page size 4KB and total physical RAM of size 8KB. What will be the size of the page Table ...
Arpan's user avatar
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How synchronous and asynchronous signals are different?

A process can receive two kinds of signals classified based on the source and reason. Synchronous are the one that are generated by illegal memory access or division by zero. Asynchronous are the one ...
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Who and how generate the virtual/logical addresses? Confusion if it's the compiler, the linker, the loader

I know that when I compile a program and then I inspect with objdump, I have addresses. These are relative addresses. But if it's a C program and I printf with <...
Allexj's user avatar
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How does virtualization handle modern TLBs?

In an answer to this question: For instance, modern Intel TLBs have a process context ID (PCID); each TLB entry is tagged with the PCID of the process that the page mapping is for, and the processor ...
whoisit's user avatar
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Order of releasing the semaphores

I was studying the dining philosopher problem (See problem description) and its solution using semaphores, and I came across this : ...
Girik Garg's user avatar
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Can a MMU be emulated entirely in software?

I'm curious about the viability of creating memory isolated processes on a processor without an MMU. While it would be inefficient I'm wondering if it's possible to basically create a virtual machine ...
FourierFlux's user avatar
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Concurrency in Operating System

I had the following question in an exam: Which of the following best describes the concept of concurrency in an operating system? Options: The ability to execute multiple programs simultaneously. The ...
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Oldest Operating System still in use today?

Reading through https://en.wikipedia.org/wiki/Timeline_of_operating_systems to decide where to port some library software—network|crypto|archive abstracting—I'm writing in C (C89). DOS is definitely ...
Samuel Marks's user avatar
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Bankers Algorithm - maximum number of processes

I recently got the following question in my exam. Q1) In the banker's algorithm, if the total number of resources in the system is 20 and the maximum resource allocation for a process is 5, what is ...
ray an's user avatar
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Which searching technique will cause lesser number of page fault?

Linear Search has O(n) T.C and Binary Search have O(logn) T.C. But how come Linear Search generates fewer page faults? Is there another searching technique that causes a lesser number of page faults ...
Vedant Khandelwal's user avatar
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What are the main differences in file implementation between linux ext4 and wi dows 10 ntfs at low level?

I need help with this is possible. Could someone who has a good understanding of Linux and Windows explain how they differ in file implementation foxuing on low level end? There isn't a huge amount of ...
luke 112472's user avatar
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How can I connect a drive to a 16 bit custom intel 8088 system?

I'm embarking on a long-term project, aiming to build a computer based on the Intel 8088 architecture. This venture provides an excellent opportunity to deepen my understanding of computer hardware ...
Grizzly's user avatar
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What is a real life analogy of busy waiting by process "i" when "turn=i"?

...
Team B.I's user avatar
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Process Synchronization and Atomic Instructions

According to the book " Operating Systems Concepts ", ninth edition , page 210, we have the following statement : Many modern computer systems therefore provide special hardware ...
John adams's user avatar
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Roles of 80386 MMU Paging Unit and similarity with modern CPU MMU

While searching for the structure of the MMU, I found the image below (80386 Internal Architecture). I have three questions. Q1. I'd like to know the roles of 'Adder', 'Page Cache', and 'Control and ...
W298's user avatar
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What happens for hardware Interrupts in non-preemptive scheduling?

In non-preemptive scheduling, the running process cant be interrupted .But what will when the CPU receive a hardware interrupt such as the an interrupt from the printer indicating that the current ...
John adams's user avatar
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What is point of calling syscalls in the kernel?

If syscalls are meant to transition into kernel mode from user mode, what is the point of calling syscalls in the kernel? Reference: https://stackoverflow.com/questions/15841327/can-we-call-system-...
tbhaxor's user avatar
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Which queue does `wait()` suspended process goes into?

According to javatpoint, ready and wait queue are different. But according to wikipedia they are synonymous, in this context. Now I am more confused. What I want to know is, when the parent process ...
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Processes with communication exclusive from the OS

Most OSes use the message passing system to let 2 processes communicated with each other.This works by a shared mailbox between the OS and each process loaded in the RAM however are there processes ...
Cerise's user avatar
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Two-Level Threading Model

In multithreading models, we have a two-level model in which we multiplexes many user-level threads to a smaller or equal number of kernel threads but also allows a user-level thread to be bound to a ...
John adams's user avatar
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Process Control Block

As we know, the operating system maintains a data structure for every process called process control block. My question is where this data structure is stored inside the OS ?
John adams's user avatar
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A question about layered architecture in OS

In layered architecture, the operating system is broken into a number of layers (levels). The bottom layer (layer 0) is the hardware; the highest (layer N) is the user interface. Each layer is ...
John adams's user avatar
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Understanding the Relationship Between CPU Registers Amounts and Maximum RAM in 32-bit Architectures

To my knowledge, The number of CPU registers can tell us the maximum RAM we can have. I am only talking about physical memory, no virtual memory or virtualization in my question. A 32-bit CPU ...
Ahmad Addas's user avatar
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1 answer
152 views

What is the difference between Application Programs and System Programs?

In Operating Systems, What is the difference between Application Programs and System Programs? Also, what are examples of each?
John adams's user avatar
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158 views

Device Controllers in OS

According to this article, we have the following: The device controller gets data from a connected system device and temporarily saves such data in a special purpose register inside the controller ...
John adams's user avatar
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Is the OS kernel part of the main() of the OS or is it a seperate function?

I am wondering is usually the OS kernel which provides a link between 2 processes part of the main() of the os or is it a seperate function?In other words do we usually encapsulate the OS kernel in ...
Cerise's user avatar
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Is communication between processes really important for a OS or is it just a convenience?

One of the services of a OS is communication between processes.However how much important is that?I dont think it is that important just for example if we saved a .txt file the file explorer wouldnt ...
Cerise's user avatar
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Why when we use DMA , Read/Write operations on I/O devices are faster?

I am wondering why are read/write operations on I/O devices much faster when we use DMA?I must be that when using DMA we have 1 less clock cycle to access the local buffer of a IO device since it is ...
Cerise's user avatar
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Why can't we mount multiple filesystem in same mountpoint?

Systems impose semantics to clarify functionality. For example, a system may disallow a mount over a directory that contains files; or it may make the mounted file system available at tha directory ...
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Trapframe vs Scheduler Context in Process Management

So a process have scheduler context and trapframe and both of them are allocated in the kernel stack (kstack). When process wants to transition from user mode to kernel mode, usually due to traps (...
tbhaxor's user avatar
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How does garbage collection works in operating systems?

As per the author, ...In this case, we generally need to use a garbage collection scheme to determine when the last reference has been deleted and the disk space can be reallocated. Garbage ...
Team B.I's user avatar
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How is the physical address calculated in Page tables?

Taking an example, say we have Page size = 4KB, Page Table Entry = 4B, Physical Address Space requires 36 bits In 3-level multi-paging, let's say the number of entries in the level 3 page table is 2^9 ...
parsingstreet's user avatar
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What is the optimal resource to follow to learn Operating System?

I wanted to learn Operating System on my own. Although I have learned few basic things from here and there, but wanted to know the suggestions (books, any video lecture, etc.) from this community.
harshmangalamv's user avatar
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Size of the page table

Question Consider a system which has logical address is 7 bits, physical address is 6 bits , page size is 8 words, calculate the number of pages and no.of frames, size of page table. Answer Addressing ...
Saket Singh's user avatar
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1 answer
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Deadlock in LockTwo Algorithm

I was reading the Book: The Art of Multiprocessor Programming; Section 2.3.2. and I have a doubt regarding their $\texttt{LockTwo}$ algorithm mentioned in Page 26. The snippet of the algorithm is: <...
Equation_Charmer's user avatar
1 vote
1 answer
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How exactly does stale data appear in temporal buffer in Downfall attack?

I've read Downfall paper. In the university, I've had an introductory course on computer organization and operating systems. We also studied Spectre and Meltdown attacks there. I understood the ...
Borisav Živanović's user avatar
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Protection in OS

According to the book " Operating Systems Concepts " , 9th edition, page 637, we have the following statement : Rather than associating the columns of the access matrix with the objects as ...
AAA's user avatar
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2 answers
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What exactly is stored in dynamic linking

I read that in dynamic linking we store the references to the the methods of the library , but a library is essentially a collection of files , and every file will have some code in it , so the ...
green_32's user avatar
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How can I solve the error "Kernel Power EventID 41"?

My laptop started doing this recently It does this sometimes when I wake it from sleep /standby. It just restarts. And sometimes when I turn it on (from having it properly shut down the day before). ...
Shion's user avatar
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What if the size of the logical address is not power of two?

If the logical address and the page size are power of two, then we can separate the virtual address into two parts: page number and offset. Is this still valid if the virtual address is not power of ...
AAA's user avatar
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How does this swap instruction achieves mutual exclusion, progress and bounded waiting if it does?

...
zeeshanseikh's user avatar
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How are waits in semaphores made atomic in nature?

I was going through the book Operating Systems by Galvin. First they explain Semaphores acting like a mutex. While talking about semaphores as mutex, they mention that the wait operation of semaphores ...
Himanshuman's user avatar
2 votes
1 answer
89 views

Nonpreemptive kernels in OS

According to the book " Operating Systems Concepts " , 9th edition, page 207, we have the following statement : Obviously, a nonpreemptive kernel is essentially free from race conditions on ...
AAA's user avatar
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