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Questions tagged [operating-systems]

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

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1answer
189 views

How to Identify which instructions are represented by this microcode

I'm having issues with a question how to identify which instruction are represented by this microcode. The pc starts at 5000 and 7000 and 7001 have values 31 and 64 - I'm really confused how to ...
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4answers
4k views

How does an operating system implement the C library?

I have an idea of how a C program is turned into machine code by the compiler. I also know how the processor processes the instructions (https://www.youtube.com/watch?v=cNN_tTXABUA this video has a ...
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1answer
104 views

How does a buffer overrun corrupt the return address?

I got stuck on the following note while reading a paper about computer security: The stack mixes program data and control data – by overrunning buffers on the stack we can corrupt the return ...
14
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2answers
8k views

Performance of microkernel vs monolithic kernel

A microkernel implements all drivers as user-space programs, and implements core features like IPC in the kernel itself. A monolithic kernel, however, implements the drivers as a part of the kernel (e....
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1answer
624 views

What does an “I/O Task” mean?

While reading an article, I noticed the use of term 'I/O Task': Indeed, suppose the currently running process is performing an I/O task (which, by definition, does not need the CPU to be ...
1
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1answer
58 views

How does the OS detect B&B violation from hardware?

After reading about Base & Bounds memory protection mechanism from Stanford CS140 lecture notes, I understood from the explanation below that there is an ...
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1answer
3k views

What does 'relocation' mean?

I am reading about Base & Bounds memory protection mechanism, and I noticed the use of the term 'relocation' in the context of ...
2
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1answer
312 views

Does starvation freedom imply progress?

The above answer taken from the book https://www.amazon.com/Operating-Systems-Sibsankar-Haldar/dp/8131730220 says starvation freedom may not imply progress as processes can be deadlocked. I think ...
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2answers
1k views

Does MMU contain and manage CPU caches?

I read about Virtual Memory in various CS references, however I'm still not sure whether CPU caches such as TLB, L1 and L2 are ...
3
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1answer
1k views

The meaning of 'Pool' in Computer Science

While reading about SIMD on Wikipedia, I noticed the use of the technical term Pool in the figure below: I didn't know what it ...
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1answer
353 views

Determine deadline for periodic task that enter ready queue in RTOS

I am currently trying to optimise the scheduler of FreeRTOS and in general Real-Time Operating Systems as a Project. In FreeRTOS, and I suspect other RTOS as well, we don't specify the deadline for ...
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1answer
440 views

Virtual Memory - Non-contiguous Memory Allocation

I'm studying for my operating systems final, and one question that my professor asked that I can't seem to find the answer to is the following: "Why does virtual memory use non-contiguous memory ...
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3answers
2k views

What does “map” mean?

I have encountered the term many times, in various CS education materials: L2 CS162 (UC Berkeley): Memory-mapped I/O L4 CS162 (UC Berkeley): Memory mapped files L24 CS61 (UC Berkeley): “...
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1answer
495 views

External fragmentation in fixed size partitioning

Can external fragmentation occur in fixed size partitioning ? I searched everywhere but couldn't find a sentence which says external fragmentation is not possible in fixed size partitioning. Please ...
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1answer
561 views

Does interrupt (for I/O and etc) requires support of Preemption? What is the relation between interrupts and Preemption in O.S?

So i just don't understand the relation between interrupts and Preemption in O.S? For example in Multi-programming, do we need the support of Preemption or not? when a process needs I/O and sends an ...
3
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1answer
158 views

Are Test and set primitives as powerful as semaphores?

I get confused because i don't know if it is possible to use Test and Set primitives in case where more then one process can be enter in critical section at the same time.
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0answers
27 views

Deadlock necessary conditions [duplicate]

I read that the 4 conditions for deadlock prevention are necessary conditions and not sufficient. The four necessary conditions are :- Mutual exclusion. Hold and wait. No preemption. Circular wait. ...
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2answers
217 views

Why are programs executed in main memory?

Why are programs kept in main memory for execution? As per my understanding, we need a memory management scheme to manage several processes in the main memory. These things can be done in secondary ...
2
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1answer
70 views

Existence of Real-Time Multiprocessor Schedule

Does an algorithm exist to check for the existence of a Real-Time Multiprocessor Schedule for aperiodic hard tasks(all of which have the same Release time)? Assumptions: The processors are Uniform ...
2
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1answer
109 views

hardware interrupts and context switch

I have recently studied about interrupts and context switch i have read that the hardware interrupts cause the interrupt service subroutine to execute for this i read mixed articles saying that there ...
2
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0answers
44 views

Can you read a file as a binary number?

This is a pretty naive question, but I would like to better understand the basics of information storage on a computer. I am not concerned with the detail of how any one operating system achieves ...
1
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0answers
321 views

Difference between inverted page table and a standard one?

I know that for standard page tables each process would have its own page table and for inverted the OS would have it. But other than this what are the main differences between a standard page table ...
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1answer
2k views

what is the need for valid/invalid bit in paged memory technique?

How is the valid/invalid bit in paged memory useful? I am not able to understand the significance. Is it also somehow used to share the processes among different users.
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0answers
72 views

Default scan order in SCAN and LOOK disk scheduling algorithms

I've been learning various disk scheduling algorithms in Operating systems. I wanted to know if there was any default scan order in SCAN, C-SCAN, LOOK and C-LOOK algorithms, like towards higher ...
2
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1answer
775 views

Operating system maintains copy of page table for each process

I am quoting a paragraph in Operating System Concepts by Silberschatz, in paging chapter, In addition, the operating system must be aware that user processes operate in user space, and all ...
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3answers
496 views

How can a spinlock progress when it's busy-waiting?

I read that in spinlock, process keeps on waiting for the lock continuously in a loop until it receives signal(lock) or ...
5
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2answers
3k views

Do system calls always means a context switch?

When a system call takes place some kernel code must be executed. If some kernel code is being executed it means it can alter register values. So before this code gets executed the old process state ...
4
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2answers
4k views

Why is the Mean Time To Failure of multiple disks calculated via division and not multiplication?

I am reading about disk redudancy. I read the following: Suppose that the mean time to failure of a disk is 100,000 hours. Then the mean time to failure of some disk in an array of 100 disks ...
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0answers
1k views

Resource Allocation Graph Algorithm

In the book Operating System Concepts, it is said that: A claim edge $P_i \rightarrow R_j$ indicates that process $P_i$ may request resource $R_j$ at some time in the future. [emphasis added] ...
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1answer
734 views

Signed and Unsigned Loads in a 32-bit Registers

I have a question over this quote directly out of Computer Organization and Design, 5e: Signed versus unsigned applies to loads as well as to arithmetic. The function of a signed load is to copy ...
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1answer
3k views

Operating System: Performance of Demand Paging

I am reading Operating systems from the book "Operating System Concepts" by Peter Baer Galvin, 7th edition. Performance of Demand Paging: Let p be the probability of a page fault (0 $\leqslant$...
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0answers
126 views

Why TurnAround Time is considered as Performance Metric for Scheduling Algorithms?

I know what is turn around time but i am confused why wating time is not considred as Performance Metric for Scheduling Algorithms Since it gives the time for which a Process will wait till it gets ...
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1answer
2k views

What is “time-slice multi-threading”?

My goal is to understand the exact differences between SoEMT, SMT and "time-slice multi threading". Thus far I already found information on SoEMT and SMT and it does not seem to hard to find more on ...
1
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2answers
42 views

If you increase the address space for an OS, does the Phys Mem used by the program increase?

I am learning about the OS. I know: that Address Space Size = # of pages x page size So if I increase Address Space Size, then the number of pages increases:(not the page size). However, isn't the ...
17
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3answers
1k views

What guarantees do “soft” real-time operating systems actually provide

I think I know what a "hard" real-time operating system is. It is an operating system with a scheduler that provides a contract with the application programmer. An application provides a deadline ...
2
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2answers
2k views

Does a simple calculator require an operating system?

I don't mean a TI-84 type calculator, and I also do not mean a simple calculator app on your phone. Does a basic scientific calculator require an operating system?
2
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5answers
15k views

How to determine the maximum RAM capacity for an operating system?

I was curious to know what limits the max RAM capacity for an OS while reading about microprocessors being 32-bit and 64-bit. I know that limit for 32-bit OS is 4GB and for 64-bit OS is 16 Exabytes, ...
2
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1answer
47 views

Should we assume both processes are getting same CPU clock while we solve SYNCHRONIZATION problems in uniprocessor system?

In synchronization, when one process is in a critical section & another is busy waiting, both are using CPU. But in a uni processor system, in the same clock both cant get the CPU. So there must ...
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1answer
2k views

Process Synchronization: Dekker's algorithm

This Screenshot is taken from William Stalling's Operating Systems book. My doubt is that Bounded wait is not satisfied by this solution. For example: P0 and P1 both want to enter critical section ...
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0answers
418 views

Physically indexed virtually tagged cache

PIVT cache is indexed physically so address translation using TLB is needed to get into cache and we use virtual address as the tag for comparison . I read that homonym is a problem which is caused ...
2
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3answers
1k views

Round Robin Scheduling

I understand that a big advantage of round robin scheduling over non-preemptive schedulers is that it dramatically improves average response times. By limiting each task to a certain amount of time, ...
1
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1answer
56 views

Program counter format LC-2

Not really sure if this is an exact CS question. I'm reading the Patt/Patel Introduction to computing systems Powerpoint presentation and I don't understand about the program counter and instruction ...
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0answers
252 views

Internal fragmentation basic concept

Suppose I have two processes of 50 bytes and have only one partition (hole) of 100 bytes. Suppose the first process takes up the partition and 50 bytes is remaining . Can the second process reside in ...
2
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1answer
149 views

Numerator of HRRN scheduling formula

In the HRRN scheduling, priority formula is P = (W+E)/E , where W: waiting time and E: estimated run time. CPU finds the job that has highest priority value and does that job. However, the formula ...
1
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1answer
48 views

Is the term page replacement actually a misnomer?

My understanding is that "page replacement" entails replacing the contents of a frame to bring in a new frame in it's place corresponding to a new page. Since it is not the page, but the frame that ...
2
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3answers
62k 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 ...
0
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0answers
68 views

What happens when accessing 0x00ABBA?

Given the following page table with a 24 Bit virtual address and 4KB page size and 4 byte long entries (%X means hexadecimal values): I don't understand how to translate e.g. address %X00ABBA here. I ...
3
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3answers
9k views

Highest Response Ratio Next (Scheduling Algorithm)

In CPU scheduling HRRN(Highest Response Ratio Next) algorithm chooses the next process to be scheduled using the formula (W+S)/S where W-> waiting time & S->Service Time. Can someone share their ...
2
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2answers
1k 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 ...