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

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Which combination of the following features will suffice to characterize an OS as a multi-programmed OS

Which combination of the following features will suffice to characterize an OS as a multi-programmed OS? More than one program may be loaded into main memory at the same time for execution. If a ...
3
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3answers
2k views

A multi-user, multi-processing operating system cannot be implemented on hardware that does not support

A multi-user, multi-processing operating system cannot be implemented on hardware that does not support Address translation DMA for disk transfer At least two modes of CPU execution (privileged and ...
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1answer
46 views

How many pages does the page table require?

I have found this exercise on the Internet but I´m having problems with sections 4 and 5, because I don´t understand where do the solutions appear from. Example: Mapping VAs to PAs Suppose - ...
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1answer
24 views

Computer Organization and Architecture [closed]

I want to learn Computer Organization & Architecture on a self basis. But I have no idea, from where should I start and which topics should I cover? After that I want to study operating systems ...
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1answer
21 views

Difference between word logical addressing and byte logical addressing in this exercise?

I´m new here and this is the first question I´m posting (hopefully this is the correct site). I have the exercise below: Consider a virtual address space of 10 pages of 1024 words each (1 word = 2 ...
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0answers
53 views

Indexed allocation in operating system file management

In the index allocation scheme of blocks to a file, the maximum possible size of the file depends on : Options: A]The size of the blocks, and the size of the ad­dress of the blocks. B]The number of ...
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0answers
18 views

clustering disk pages In the most I/O efficient manner

Let's suppose there're consecutive 5 disk pages (each disk page size = 8KB). P0 P1 P2 P3 P4 Among those 5 pages, we need to read P0, P1 and P3. There are three ways to load those pages: [1] Issue ...
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0answers
41 views

How do stack-based cache algorithms avoid Belady's anomaly?

I was going through page replacement algorithms from Galvin's Operating System book. I encountered this line about LRU: A stack algorithm is one in which the pages kept in memory for a frame set ...
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0answers
18 views

When was manual dynamic memory managment introduced?

Original Fortran only had static memory. Algol introduced stack allocation. Lisp had Garbage Collection. But when where manual dynamic memory management such as in C introduced. In C memory can be ...
0
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1answer
38 views

Where does the process reside in memory?

When a program runs in CPU, it turns into a process. In what kind of data structure is the process stored in a system memory? Heap or Tree or some other data structures?
1
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1answer
38 views

What type of an algorithm is being used for directory structure scanning?

So after learning about DFS and BFS yesterday in my class I was curious as to how is scanning on various file system being done. I spent quite a bit of time trying to look for some references on the ...
0
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1answer
25 views

Not sure about a part of an answer - page table size question

Below is a question and answer that I'm reviewing. I understand most of it but I'm not clear where the 8 bits for the PTE size came from in this part... ...
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1answer
22 views

What happens under the hood when the process requests operating system to open a file?

Suppose a process wish to open a file named test.txt. So it issues a system call requesting Operating system to find the file on disk,and to grab the handle of file to operate on it. My question is ...
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1answer
30 views

Effect of Copy-On-Write on 2 processes sharing address space

I am studying operating systems and was going through Copy On Write mechanism. From Wiki: When one process modifies the memory, the operating system's kernel intercepts the operation and copies ...
1
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1answer
15 views

How does Logical Block Addressing affect OS disk scheduling optimizations such as SCAN (Elevator Algorithm)?

If the OS is scanning from one edge of the disk to the other, doing so from behind the Logical Block Addressing (LBA) abstraction, although it may aim to service requests in an elevator-like way, what ...
0
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2answers
48 views

Key differences between interactive and time sharing operating systems?

Couldn't find much online on how an interactive system is different from a time-sharing system, or the different traits of both. My understanding of a time-sharing system is many people at terminals ...
1
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1answer
28 views

Address space definition

I'm learning by my self about OS theory and I have some troubles to understand what is a process address space. So far, I came across two definitions of what a process address space is: 1 - The set ...
1
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1answer
43 views

What are logical addresses and where do they actually reside?

While studying about memory management, paging and segmentation there is a lot of usage of phrases like CPU generates logical addresses and ...
0
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1answer
61 views

finding maximum virtual and physical memory

If the following is given: CPU uses a four-level hierarchical page table, each level can contain 512 entries the page size is 4KB. virtual address is 48 bits How do i get the size of the ...
1
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1answer
34 views

How does the OS Scheduler give/take control of HW?

Imagine a uniprocessor system with a simple operating system with non-threaded processes and basic virtual memory (paging, no segmentation, no replacement to disk, etc). Now assume a simple ...
3
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1answer
28 views

Why do ACLs (access control lists) have better persistence than capabilities?

Although I understand the principles on which both ACLs and Capabilities operate, I do not see why on system restart it would be favourable to store privileges by using ACLs, instead of capabilities ...
1
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1answer
53 views

Confusion in Banker's Algorithm: How resources are allocated?

I have seen examples about Banker's Algorithm from this Wikipedia link, this book and many other places. In all these examples some processes are allocated ...
0
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1answer
46 views

Is emulation and/or virtualization faster when the host and guest systems are more similar?

Is emulation and/ or virtualization performance faster when the guest and host OS are similar? If yes, how big, relatively speaking, is the difference? And whether the answer is yes or no, why is it ...
3
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1answer
43 views

Deadlock avoidance: How does the system know in advance about the number of resources required by a process?

While studying about Deadlock Avoidance I came across a paragraph which states as given below: When the system needs to issue any resource to any process, then ...
2
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1answer
42 views

How does RAID-5 algorithm locate the right device?

Please consider the following diagram of a RAID-5 array (Ignore the gray background): Now, given a logical address, how can one return the device number (0-3)? For example, DeviceByLogicalSector(50)...
3
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1answer
48 views

What is the difference between “deadlock prevention” and “deadlock avoidance”

I have studied about both of these on many places like this, this and this, but still it is not that much clear that what the actual difference is between these two. The Wikipedia links (first and ...
3
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1answer
33 views

Falsifying the “Circular Wait” Condition - Deadlock Prevention

In the Circular Wait condition for Deadlock Prevention section of this, it is described as follows: One way to ensure that this condition never holds is to ...
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2answers
40 views

Language that system calls are implemented in

Lately, I have been reading about operating systems design. The idea that all user space programs utilize Kernel services via a "System Call Interface" have got me thinking further into this. Is ...
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1answer
28 views

Two threads are waiting on a mutex. Which one is unblocked?

Suppose there are three threads A, B, C and thread A has acquired a mutex lock and it is processing. If threads B and C try to acquire the same mutex, they will be blocked according to the mutex lock ...
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1answer
27 views

Confusion in the solution to first readers-writers synchronization

I am studying the solution to “First Readers-Writers Problem” from the book Operating System Concepts (9th edition) and it describes: First readers–writers problem, requires that no reader be kept ...
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1answer
26 views

How to choose waiting process in a preemptive priority-based scheduler

If my CPU schedule is preemptive priority, and I have no new processes coming, how I should choose from the waiting processes?
3
votes
2answers
54 views

Why is word-addressable the exception, not the rule?

As stated on Wikipedia: Most modern computers are byte-addressable instead of word-addressable. Why is this case? Since the CPU processes words (of predominantly 64 bits or 8 bytes) now, wouldn'...
0
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0answers
20 views

What are the parts of an object module and how do they work with a linker?

I'm trying to figure out how a linker works (after the compiler and assembler have finished processing a module). In my class notes we are given an example of a target machine that is word addressable ...
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2answers
55 views

What's the difference between clock replacement & LRU replacement?

As title. When we want to request following page numbers 2,4,4,2,5,2,1,1,3,1, is clock replacement better? What are the advantages and disadvantages of them? Thanks~
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1answer
52 views

Why is the processes address space a continuous block in RAM?

I need some clarification regarding how the process address space is organized in memory. I went through basic concepts of virtual memory and adress translation and according to the size of the page, ...
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4answers
54 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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1answer
82 views

Difference between system calls, system call interface and API? [closed]

Lets take POSIX, whats the difference between POSIX API, libc and actual system calls?
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1answer
98 views

How and which component of an Operating System is responsible for the transition of a process from the blocked state to the ready queue?

A process in an Operating System is considered to occupy several states and a process transitions between these states. A scheduler is responsible for assigning CPU time to a process. However, a ...
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1answer
98 views

Deleted data remains on a disk until? [closed]

I am little bit confused between the two answers below. What is the exact answer of this question? My query is, "Deleted data remains on a disk until...?" The data is overwritten; The recycle bin ...
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1answer
117 views

What's the difference between Process Context and Process Control Block?

I know that Process Context is something that is stored when a process is preempted, containing all the necessary info to restart the process at a later time. I also know that the Process Control ...
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1answer
43 views

Which process comes first?

Let's say we have 3 processes: Process 1 service time 6 arrival time 0 Process 2 service time 2 arrival time 1 Process 3 service time 5 arrival time 3 We know that: after 1 time, process 2 will ...
2
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2answers
319 views

Virtual Address and Physical Address Space

A machine has 48-bit virtual addresses and 32-bit physical addresses. Pages are 8K. How many entries are needed for a conventional page table ? The answer is 2^35 entries Why not (2^32) / (2^13) = ...
0
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1answer
113 views

Can you explain this exercise solution to me? [closed]

A process running on CTSS (Compatible Time Sharing System) needs 30 quanta to complete. How many times must it be swapped in, including the very first time (before it has run at all)? • Answer : The ...
2
votes
1answer
361 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
41 views

How can another process call $signal()$ when one process is executing $wait()$ in its busy waiting loop?

A semaphore is a variable that, apart from initialization is accessed through only two standard atomic operations wait(s) and signal(s). ...
1
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2answers
113 views

Difference between virtual memory and job pool

Both virtual memory and job pools store the processes temporarily on disk and bring them to memory at some later stage, so what is the actual difference in between them? What I guess is that when a ...