Questions tagged [operating-systems]

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

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Exception handling

In problem 1 part D) of https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-004-computation-structures-spring-2017/c17/c17s3/os_answers.pdf, how come process 1 is never scheduled?...
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Flow of control when calling a function

I am learning about embedded and operating systems. I would like to know the order of control flow that occurs when a user-space C application calls a function, for example, printf(). I am slightly ...
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Why does an inverted page table keep a chain of pages per frame when it can only store one of such pages?

I'm currently dealing with inverted page tables and how they work. If I understood correctly, an IPT is a table that maps a frame number to a PID and page number. The way this works is by having a ...
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Simultaneous buffer access in the bounded buffer problem

Galvin and various other resources only allow either the producer or the consumer to access the buffer at a time, the common code is as follows: ...
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How a swapper manipulates entire processes in the operating system?

The below-given lines are written in the book of the operating system (Page -307), details of the book are as follows: OPERATING SYSTEM PRINCIPLES, 7TH ED., Abraham Silberschatz, Peter Baer Galvin, ...
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Fixed partitioning and dynamic partitioning process allocation

If I have a process leave of 10KB and only that 10KB is free then 2 processes of 2KB and 6KB enter into the memory will only one process get allocated or both in the same hole. Please answer with ...
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IoT OS running on top of Ubuntu?

I am new in the field of IoT OS and I saw TinyOS, Conitki etc. can be installed on top of Ubuntu. Its not clear to me how these OSes are able to run on top of Ubuntu without any Hypervisor? Can ...
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Why do OS locks require hardware support?

I just read the chapter on locks in the book Operating Systems: Three Easy Pieces, and it discusses an implementation of locks (see in Figure 28.9) that involves a test-and-set hardware instruction. ...
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What does it mean having a 64 bit operating system or x64 based processor

I checked in my computer's setting and found out that I have a 64-bit system. What does this actually mean and does it have more benefits than a 32-bit system?
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Early Deadline First (EDF) scheduling in real-time systems feasibility test proof

I am trying to prove Theorem 6.2 on page 127 of the book Real-Time Systems by Jane W. S. Liu: http://www.cse.hcmut.edu.vn/~thai/books/2000%20_%20Liu-%20Real%20Time%20Systems.pdf It is based on Early ...
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How were operating systems even made?

By that, I don't mean what is needed to make an operating system. I know that OSes are built on top of kernels and whatnot. But what I mean is, it wasn't like anyone could just "program" the ...
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What does starvation freedom exactly mean?

Galvin offers the following definitions of starvation: Indefinite blocking, or starvation, a situation in which processes wait indefinitely within the semaphore. A major problem with priority ...
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I want to learn more about computer science. Where should I start?

Hello computer scientists, I am a mathematician. I have taken some undergraduate courses in C++, Python, assembly language, boolean algebra, logic, graph theory, etc. I would like to learn more about ...
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Is vmlinux a virtual machine?

From Wiki, On Linux systems, vmlinux is a statically linked executable file that contains the Linux kernel Does that mean vmlinux is a virtual machine that runs ...
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the difference between Idle point and Idle slot

I believe that I don't understund well the difference between an idle processor point and an idle slot Thanks
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Gantt chart for Round Robin Scheduling using only arrival and completion time

I had the following question in my Operating System 'CPU- Scheduling' assignment- 4 processes A,B,C,D have estimated time of completion of 5,7,9,11 ns each. They are scheduled in a round-robin fashion ...
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Confused between the terms Process and Process Control Block

I was reading about the Long term scheduler, when I read that when memory is not enough and load on the CPU due to multiprogramming is too high, a process might be moved to secondary storage space (...
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why you couldn’t use mmap to manage a rdbms buffer pool - or the whole rdbms itself just like NoSql stores?

why you couldn’t use mmap to manage a rdbms buffer pool - or the whole rdbms itself just like NoSql stores? I see that Cassandra, Hbase, Elastic do use mmap so why not use the same strategy for an ...
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Round robin doubt

Consider a system running ten I/O-bound tasks and one CPU-bound task. Assume that the I/O-bound tasks issue an I/O operation one for every millisecond of CPU computing and that each I/O operation ...
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Operating system scheduling doubt

Consider a uniprocessor system executing three tasks T1,T2 and T3 each of which is composed of an infinite sequence of jobs (or instances) which arrive periodically at intervals of 3, 7 and 20 ...
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Why can't we compile 8086 Assembily for all OSs from any OS?

If Mac OS, Linux, and Windows (mostly) all use Intel's 8086 64 bit instruction set, why can't we compile 8086 64 assembly from any operating system to any other operating system? (e.g. compile a Mac ...
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A 32 – bit wide main memory unit with a capacity of 1 GB is built using 256M X 4-bit DRAM chips

A 32 – bit wide main memory unit with a capacity of 1 GB is built using 256M X 4-bit DRAM chips. The number of rows of memory cells in the DRAM chip is 2^14. The time taken to perform one refresh ...
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Storage in registers

Whenever CPU needs the data, it gives the address of that word to the RAM via bus, then the RAM generated the copy of that word and sends to the registers via bus. Why can't the RAM send the original ...
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memory storage of a program before compiling

Whenever we write code, after compilation the code will be converted to machine language and then stored in the hard disk. But before compiling the code, it is still in the high-level language. How ...
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Do all processes are allocated equal sized page map tables?

I have a simple question : In a paged memory system, all processes are allocated equal sized page map tables ?
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Question regarding the one and two level paging system

I am studying for my OS final exam and I am solving some problems related to virtual memory . however , I have faced a problem which I need to test my understanding regarding it : ...
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Paging only for user code. What about kernel code?

Why is paging done only for user code (user space)? I know that the basic intuition behind paging is for managing larger logical address space in smaller physical main memory space. Won't the kernel ...
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PSH flag in TCP header send a singal to the receiver process?

we know that when TCP data is received with PSH set, it will immediately transfer the received data to the application.and let's when pushed data arrives the receiver side and the receiver application ...
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Multi-level paging where the inner level page tables are split into pages with entries occupying half the page size

A processor uses $36$ bit physical address and $32$ bit virtual addresses, with a page frame size of $4$ Kbytes. Each page table entry is of size $4$ bytes. A three level page table is used for ...
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How to calculate the size of the page table of a process?

Consider a system with A bytes of physical RAM, and B bytes of virtual address space per process. Pages and frames are C bytes in size. Every page table entry is P bytes in size. Calculate the size of ...
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Can User Level Thread read/write Kernel thread?

As far as I read in a OS text book (Operating Systems by Silberschatz) Kernel mode is for privileged task, so it it true to claim that "User Level Thread can read/write Kernel threads" ? ...
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How does the OS handle multiple stacks in its physical memory?

Without assuming ASLR... Processes have virtual addresses, and they manage stacks & heaps of their own. However, these all get mapped to physical addresses somewhere on the memory. Let's say we ...
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Can application DNS requests bypass a firewall on Windows and Linux

Assuming I have firewall set to block an application from accessing the Internet, would I DNS request go through? I tried using C (gethostbyname) on Windows and the answer is no. It seems that the ...
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Context switch in an Text Editor

I am new to operating systems and have been wondering about this. Consider a normal text editor, and it's process running in the CPU. Since text editors include IO operations, do the process keep ...
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page table size in a 1 and 2 levels page table

Consider that virtual page numbers are 36 bits, and page table entries, as well as pointers to other page tables are 4 bytes each. First , if we need to calculate how much memory would a single level ...
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Operating Systems - Page Table - Address Translation - Physical Address & Logical Address

Hi, I am learning about memory management in operating systems. I am confused with Address Translation. In this question (pic attached), can anyone explain, how the answer is obtained for Blank #2? ...
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How can 4 GB of data can expand into 40 GB of data, when I install Windows on a Computer

Say I start with an iso with about 4GB of data and use this, to install windows on a computer. After installation, the operating system will take up about 40GB of disk space. Where does all this &...
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How multiprocessing is done in Single Core Systems?

Can we do multiprocessing on single core system ? I thought that single core means that ONLY one process/thread can execute at any time. For multiple processes , there can be concurrent execution to ...
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What is the difference of Process synchronization management between Windows and Linux?

I am looking for some explanation about process synchronization management in windows OS and Linux OS and what they do about the critical section and mutual exclusion. I will be so grateful if someone ...
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Understanding Cyclic Dependencies when using Soft Update for Filesystems

We recently delved into the concept of "Soft Updates" as a mean of maintaining a Filesystem as consistent. The solution, as we learned it, calls for 3 basic rules: We'll create a pointer to a file ...
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Difference between process contention scope and system contention scope

According to my understanding the difference between them is that in process contention scope there is a contention within the process for mapping user threads to kernel threads and for system ...
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Is process address space part of Process Control Block(PCB)?

I recently read about the process address space and PCB and trying to link them together. I don't find much literature on their relation. Is the process address space a part of the PCB data ...
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Real-time systems and real-time operating systems

Just to understand the topic a little bit better, I would like to know if there is a difference between real-time systems and real-time operating systems. I know that a real-time system is a system ...
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Is there any operating system running in Graphics cards?

Taking an example of NVIDIA graphic cards, is there a dedicated OS running on the Graphic card's GPU or the Host machine's ...
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1answer
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Process synchronization problem

The atomic fetch-and-set x,y instruction unconditionally sets the memory location x to 1 and fetches the old value of x in y without allowing any intervening access to the memory location x. Consider ...
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Hierarchical page tables with page size of 8 KB

Consider a machine with a physical memory of 8 GB, a page size of 8 KB, and a page table entry size of 4 bytes. How many levels of page tables would be required to map a 46-bit virtual address space ...
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53 views

How to find a condition which leads to deadlock in non-reentrant locks

A multithreaded program P executes with x number of threads and uses y number of locks for ensuring mutual exclusion while operating on shared memory locations. All locks in the program are non-...
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When is it best to use the second chance replacement algorithm?

I'm going through 'Operating Concepts' by Silberschatz, Galvin and Gagne (The Dinosaur Book) and it mentions the Second-Chance Algorithm (not enhanced) as an improvement on the FIFO replacement ...
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Why are special instructions used to implement system calls? Why not use normal subroutine calling instructions?

The transfer of control is often completed through some type of software interrupt instruction. These special instructions result in the CPU to save the current state of the machine and transfer ...

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