# Questions tagged [operating-systems]

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

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### OS Information Protection and Security

The below text is taken from the book : Operating Systems: Internals and Design Principles by William Stallings, 8th edition, pages 67-68. Information Protection and Security The growth in the use of ...
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### Scheduling and Resource Management in OS

The below text is taken from the book : Operating Systems: Internals and Design Principles by William Stallings, 8th edition, page 68. Scheduling and Resource Management A key responsibility of the ...
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1 vote
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### Disk scheduling: Why use (C-)Scan instead of (C-)Look?

I don't get why SCAN is used when LOOK exists. Why move to the end, when there are no longer any pending requests in that direction? SCAN: In SCAN algorithm the disk arm moves into a particular ...
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### Race condition, my doubt on Peterson's algorithm vs. C

I have seen this C code showing an implentation of Peterson's Critical Section algorithm. It is obviously skeletal and hardwired for two threads but the logic is supposed to be correct in detail. ...
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### I need help in understanding the sentence

After accepting the command entered by user,the shell generates a readily executable simple command line by parsing it evaluating variables(if present),performs command substitution,interprets ...
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### Extended BIOS data area vs BDA

I am researching the memory layout/memory map in x86 Real mode and cannot seem to find much about the extended bios memory area other than usual memory address. Is it just that, an extension of BDA ...
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### Memory management with bitmaps

I am reading Tanenbaum's Modern operating systems. I am not able to understand what he means by last line in the attached image. He says that the run may straddle word boundaries in the bitmap. What ...
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### Is Starvation possible in First Come first serve CPU scheduling algorithm

Let's say if we have an infinite process that never yields such that other process dosent get to run. Since FCFS is a non preemptive scheduler does it leads to starvation
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### What is the completion time of the processes using dynamic priority scheduling?

Consider a preemptive priority based scheduling algorithm based on dynamically changing priority.Larger priority number implies higher priority. When the process is waiting for CPU in the ready queue (...
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### How executable binary can be signed?

Some devices (for example Android devices) are "locked", the bootloader checks following bootloader/software sign, right? Chain of trust. Signing technically means that the file must be ...
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### How manufacturers lock their devices to run only software by them? And how it is possible at all?

How do manufacturers lock their devices to run only software by them? And how is it possible at all? For example: upgradeable toothbrush, mobile device, smart watch
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### What does exactly Medium term scheduler do?

I'm trying to know what is the exact function in medium term scheduler in operating systems. As far my understanding, a process may be needed to be removed from the running queue when it is faced with ...
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### Do i really need to study monstrously long intel manual?

I want to be an OS developer. I can say I am a bit comfortable after i read few tutorial on x86 assembly. But I see a lot detailed in intel manual, does an OS developer really need to study whole ...
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### Meaning of "untyped bytes" in file systems

I am currently reading reading Chapter 11 of Operating Systems: Principles & Practice by Anderson and Dahlin, which speaks about file systems as abstractions for non-volatile storage. The ...
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### Difference between bare metal hypervisor and operating system

I'm currently studying virtualization and while looking at hypervisors I realized that bare metal hypervisors are quite similar to operating systems. So while from an application standpoint they are ...
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### To where is the mouse sending signals of a computer?

When we move the mouse, we can see the cursor moving on the monitor. I know that mouse can send signals according to its movements. Which component of a computer is receiving those signals in the ...
1 vote
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I am recently studying The Operation System, I am confused about how symlink work even after watching some YouTube videos, hope there's someone can help me out with some questions. According to wiki, ...
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I am recently studying the operating system, and I found the paging system a little bit confusing, for example, what will happen when there is a 52-bit virtual address and a 40-bit physical address, ...
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### Choices in cpu-scheduling decisions

I'm reading Operating System Concepts by Silberschatz and in chapter 5, there is this text: 1. CPU-scheduling decisions may take place under the following four circumstances: When a process switches ...
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### Does the Posix read() system call for FILE* have an internal buffer in the kernel?

Does the answer depend on the number of bytes requested? If it is forced to keep a buffer due to some unknown device/diver, can it optimize and skip the buffer if it's going to be a disk read? I'm ...
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### Is booting only a part of OS possible?

I am reading the paper HyperEnclave. I have a few questions about the OS in general. Is is safe to assume that attackers cannot mount physical attacks during boot process of the OS? Can we assume ...
1 vote
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### Page/Frame VS Block

I am bit confused on these terminologies. While studying Paging of Operating System we study about Page and Frame. Size of one Frame of Main Memory = Size of one Page of a Process While studying ...
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### If a process needs more RAM, does the Page size simply get bigger or does it get a new page?

Let's say I have a Operating System with 4KB page size, but I need to allocate 8kb of memory for all the variables. Does the Process get new page (second one) or does the current page table simply get ...
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### What is the difference between segmentation and dynamic partitioning in memory management?

I was reading up segmentation in memory management, and it seems similar to dynamic partitioning. What is the difference between segmentation and dynamic partitioning?
1 vote
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### How are frames split up in an inverted page table?

For an inverted page table, it's number of entries = number of frames in main memory. One frame in the main memory, could be shared by two (or more) processes, say process A and process B. Usually ...
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### Saving Process State by Writing Pages to Blocks

Why don’t operating systems save process state (registers, page tables, pages) by writing state to storage in blocks? Wouldn’t this allow for a seamless restoration of state when the process needs to ...
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### Combining fork() and algorithms

Today in my algorithms class, my professor explained how in divide and conquer algorithms we do things in "parallel" although I felt it was not exactly in parallel. Then I remembered from OS ...
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### Is kernel essentially an implementation of system calls?

In essence, is kernel basically the code that implements a set of system calls?
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### How do we run programs which are bigger than RAM itself

I know that whenever click on .exe, it will be moved into RAM so cpu can execute machine code line by line. But what if .exe is bigger than RAM? for eg: I play games which take up more space than my ...
1 vote
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### On load estimation of memory consumption of program, is it possible?

In the book "Fundamentos de sistemas operativos" (Gunnar Wolf, Esteban Ruiz, Federico Bergero, Erwin Meza p.254) it says: Al cargar un programa el sistema operativo calcula cuánta memoria ...
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### Computer Architecture MIPS assembler with predictors

This MIPS code is given: ...
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### Does optimal page replacement cause the same number of faults for the reverse string?

Let $P_1P_2...P_k$ be a page sequence that gives $n$ page faults with the optimal page replacement algorithm. Does the page sequence $P_kP_{k-1}...P_1$ give the same number of page faults. This can be ...
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In the operating systems that make use of the execution-time address binding who is responsible for the creation of logical addresses? EDIT I'm thinking that the logical addresses are generated by the ...
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### Swapping in mobile systems

I know that swapping is avoided in mobile systems because of limited memory but I came across this question and couldn't answer if the answer is yes. Should swapping be done in Mobile systems? If yes, ...
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### Need help to find some courses about system software design and development

The question's title itself says what I want. I've already searched this term on google but I can't find any course with this theme. What terms I can use to search about this course?
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### How does the kernel sends information generated by an interrupt to the right process?

Andrew S. Tanenbaum, in his book Modern Operating Systems states that, When a hardware interrupt occurs while a user thread is running, the interrupted CPU switches into kernel mode. If the interrupt ...
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### What is the advantage of a hashed inverted page table versus an ordinary hashed page table?

A hashed inverted page table has a hash table that points each page number to its frame number. This frame number can then be used as an index to the inverted page table to get the PID and page number....
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### How are interrupts handled?

Andrew S. Tanenbaum, in his book Modern Operating Systems, states that Once the CPU has decided to take the interrupt, the program counter and PSW are typically then pushed onto the current stack and ...
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### Questions regarding Translation Lookaside Buffer (TLB)

TLB is used in the paging memory scheme to reduce the time taken for memory access for a user's memory location through storing pages in this TLB cache and it depends a lot on the hit ratio (The ...
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### Why windows 11 does not support old cpu?

I know CPUs execute machine language code. Also I know operating systems such as Windows and Linux are a piece of code. But I cannot understand why Windows 11 does not run on a somewhat old CPU. Can ...
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### what is the relation between operating systems and automata theory?

I want to do some research on how machine theory (automata theory) is applied in the operating system. Also thank you for introducing useful links and books.
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I just need to check my understanding regrading two points .As was stated in the textbook "Operating systems concept " : The compile-time and load-time address-binding methods generate ...
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### Does every thread store its context in a separate PCB?

Is a thread's context stored in the process's PCB, or is a new PCB created for the thread?
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I was going through some texts and shared PPT of my university and I found the term "traffic controller" in the Process management section under the functions of an Operating System. The PPT ...
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### Understanding the difference between API, system call and system call interface

as anticipated in the title, I can't understand the difference between API, system call and system call interface. Most of all, I can't understand if the system call interface is actually a "...
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### Boot Loaders, Boot Sectors, BIOS, and GRUB

Again, I must apologize if this is "easily googlable". I have tried. My understanding is that the BIOS typically looks for the magic number 0x55aa at the end of a 512 byte sector (so bytes #...
1 vote
146 views

### How are I/O operations handled on a computer?

What does the computer do when an I/O operation needs to be done during the process? Does the message that we need to do some I/O operation directly reaches the device controller or device driver? ...
104 views

### Tigers and elephants can't drink water from a pond simultaneously, while more than one tiger or more than one elephants can drink water simultaneously

Below is a question on synchronization mechanism which was asked in an interview in Indian Statistical Institute, M.Tech CS. I got hold of it from here. There is a forest where there are tigers and ...
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### How MAC (Mandatory Access Control) model prevents trojan horse attacks?

I've heard that the MAC Model prevents Trojans to charm files on the system. How is it possible? Can somebody show any example that MAC model protects us against it?
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