Questions tagged [operating-systems]
Questions about the principles of software that interfaces between hardware and applications.
0
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1answer
21 views
Why does paging not have external fragmentation?
I have read that paging does not suffer from external fragmentation as the frames and the pages are all of the equal sizes, but when we store a last level page table in a frame at that time it may not ...
1
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1answer
43 views
How does dynamic memory-allocation exactly work?
I have wondered about profane code. Assume we are running this code on any modern System like Unix/Linux/Mac/Windows. This code is C, but it should work with every language which is close to the ...
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0answers
5 views
Why does running GHCi in Windows make it not possible to detect infinite loops? [migrated]
I'm currently reading "Haskell Programming from first principles" and there is a paragraph in the section about bottom that reads:
Let us examine a few ways by which we can have bottom in our ...
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0answers
4 views
CMD, Command line prompt in Windows. Delete all files in a specific folder except certain extensions and files with specific names [migrated]
I apologize if I tagged this question wrong.
I have started using cmd literally yesterday so, forgive me if the question is too easy. Any help is appreciated.
I need to delete 20,000+ files with 10+ ...
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0answers
13 views
Why in the Map Reduce Implementation, why not stream the records to the reducer (via TCP) as they are being produced by the mappers?
In the Map-Reduce implementation, the reducers start when all mappers finish their jobs. Why don't we stream the records from mappers to reducers while they are being processed instead? I think there ...
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1answer
100 views
How to calculate average waiting time for round robin cpu scheduling?
I have tried to calculate average waiting time for the below details there are two answers I'm getting using two methods I'm not understanding which one is correct?
The time quantum is 2
This is the ...
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0answers
28 views
Any good source explaining multiprocessor synchronization techniques and their implementation
I need to study how synchronization is done in a multiprocessor operating system, but I am unable to find a good source. I have read about it in the book "Modern Operating System" by Tanenbaum, but I ...
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0answers
16 views
Inputting values to register files
I'm trying to understand how to register files. The question below is from past exam paper:
The following diagram shows the register-file from a simple 8-bit
machine
I don't fully get register ...
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1answer
21 views
What architectural features will allow this microprocessor to access a separate “I/O space”?
I'm studying for my final and don't understand this question. Here is the full question (from Stallings 8th edition):
Consider a hypothetical microprocessor generating a 16-bit address
(e.g., ...
1
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1answer
34 views
How exactly does a CPU do process scheduling?
I know in theory how various scheduling algorithms work, such as round robin, where each process is given small time slices to run a few instructions, before the operating system passes execution onto ...
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0answers
33 views
How can an unstable kernel write a memory dump?
I always wondered how a kernel that became unstable, e.g. due to a BSOD or a kernel panic, is able to do specific tasks.
For example, if a Windows driver corrupts the stack of the kernel. It leads to ...
2
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1answer
116 views
Why do OS and DBMS have their own synchronisation mechanisms, when OS can alone do it and it sits at the bottom of DB?
I know that synchronization is important in the OS, but why do we need a separate topic synchronization and concurrency in the DBMS? The OS concentrates on program synchronization while the DBMS ...
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1answer
86 views
Single processor system supporting two running processes, A and B, with the following sequential execution patterns [closed]
Can anyone please help me with the following question?
Consider a single processor system supporting two running processes, A and B, with the following sequential execution patterns:
A: [CPU 8 ms; ...
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0answers
43 views
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0answers
21 views
Understanding Bounded Waiting
I am trying to understand bounded waiting and i have a question.
The definition is as follows:
Bounded waiting -
There exists a bound, or limit, on the number of times
that other processes are ...
0
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1answer
28 views
what is the difference between Operating system and Window Systems?
Quoting from Tannenbaum_Operating_Systems_Design :
On top of the operating system is the rest of the system software.
Here we find the command interpreter (shell), window systems,
compilers, ...
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1answer
55 views
How does operating system display decimal numbers which are stored as binary? [duplicate]
What kind of magic happen with bytes in memory?
1
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1answer
59 views
Explain in laymen terms - How do modern programs translate into machine code
I'm sure this will benefit anyone else on a computer science fundamentals back-fill journey..
I'm slowly learning Assembly and while I'm starting to understand the core of it (MOV, JUMP, etc) and can ...
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1answer
23 views
How the operating system allocated to dual-channels memory?
I learned that the boot loader transmit the operating system from Hard Disk to Main Memory during the booting process.
I wonder, today's computers are equipped with multiple slice of memory of dual-...
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0answers
239 views
LRU vs FIFO page replacement
I am wondering if there is an instance where FIFO results in less page faults than LRU. For example:
2,6,5,7...
In this string, if I have to complete it by ...
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0answers
21 views
Addresses with no memory allocated
I've read that a program can crash if it tries to access addresses with no memory allocated. But, how is it possible that an address has no memory allocated? When does it happen?
1
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0answers
51 views
Difference between present - absent bit and valid - invalid bit in a page table?
while reading I found this:
Present/Absent bit – Present or absent bit says whether a particular page you are looking for is present or absent. In case if it is not present, that is called Page ...
2
votes
1answer
62 views
Appreciation of the 5 state process model
I'm starting out in an Operating Systems module. I have a few understanding questions to think about, which will not be gone through in class.
A process state model is an abstraction (or model) which ...
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1answer
19 views
Memory Mapping Segment
I read that "Memory Mapping Segment"/"memory mapped file" is a segment of the virtual memory of a process, where a file or file-like Ressource is loaded into. It is for high performance file I/O.
I ...
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0answers
155 views
Two Process Solution for Critical Section Problem- Algorithm 1
I have started learning Critical Section Problem and its various solutions. To explain my question, let me first give a brief background of it.
The general structure for a two Process Solution for ...
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1answer
16 views
address spaces of changing processes
I read that the mapping for user-space processes is changed after each process switch. By mapping I mean the translation from virtual addresses to "real" memory address. I thought that processes are ...
2
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1answer
34 views
What does it mean " The outer level page table need not be page aligned?
The question is in context to multilevel page table. I was trying to solve numerical on multi-level paging and noticed that page size might not be same at all levels. I came across the point "Outer ...
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0answers
293 views
Difference between Response time, Execution time, and CPU time
I studied Computer Architecture from David A. Patterson and have came across the idea of Response time.
Response time also called Execution time. The total time required for the computer to ...
0
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1answer
14 views
multithreading - duration of jobs
" How long will it take for 2 jobs to complete if they're running in parallel, knowing that both have a total of 20 minutes of CPU usage time and 50% IO"
I calculated the CPU usage: ...
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0answers
11 views
Calculate for each block, the number of bytes that can be assigned to data and to pointers to other blocks
In trying to solve the following problem:
You are presented with the first 15 blocks of a secondary storage device (disk) which has a total of 30000 KB available. The linked allocation method is ...
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1answer
30 views
Threads and Operating System
In a computer, the processor executes different threads and changes between them, the operating system is a program at the end that it´s being executed by the processor, there exists the posibility ...
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0answers
25 views
If the string of N requests is repeated many times, which of the following is/are true?
If the string of N requests is repeated many times, which of the following is/are true?
I. The fewest page faults occur when M ≥ N.
II. LRU
(least-recently-used) and FIFO (first-in-first-out) will ...
0
votes
1answer
45 views
Round-Robin fashion exercise
In my Operating Systems class I have an exercise to sketch out how a round-robin algorithm would apply to a specific scenario, which is the following:
Now the correction that I was provided with by ...
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0answers
26 views
Definition of multiprogramming [duplicate]
Which combination of the following features will suffice to characterize an OS as a multi-programmed OS?
a. More than one program may be loaded into main memory at the same time for execution
b. If ...
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0answers
31 views
interrupts in operating system
Normally user programs are prevented from handling I/O directly by I/O instructions in them. For CPUs having explicit I/O
instructions, such I/O protection is ensured by having the I/O instruction ...
0
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1answer
33 views
ARM STM instruction: page fault problem with MMIO
The ARM STM instruction is described here in the ARM manual.
This instruction writes all or a subset of registers at memory locations starting from a base memory ...
1
vote
1answer
36 views
Instructing operating system - Knowing it's functionalities
TL;DR: I would like to know how a programming language, the OS and drivers work together to perform a task.
I (and we all) have used various softwares/modules/packages on the top of our OS which ...
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2answers
30 views
Who decides that process needs cpu time or not?
I wonder how does particular process gets CPU time or resources whenever it's
required to execute some instructions? When a process is in the idle state or waiting for input, it's not occupying the ...
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1answer
31 views
Is OS mode required for accessing general purpose registers
In which of the following cases a process executing in user model is required to enter into the OS mode?
(a) Decreasing the value of unsigned integer value in a register to less than 0
(b) Accessing ...
3
votes
1answer
38 views
What should be the minimum value when the two threads are executed concurrently
int count=0;
void *thfunc()
{
int ctr=0;
for(ctr=0;ctr<100;ctr++)
count++;
}
If *thfunc() is executed by two threads concurrently in a uniprocessor ...
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0answers
38 views
Relating L1 cache, TLB and main memory
Earlier while solving problems from computer organization book by Stallings, I came across the fact that
$T_a=(H_{L1})(T_{C1})+(1-H_{L1})(T_{C1}+T_M)$
where,
$T_a \rightarrow$ Average access ...
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0answers
20 views
How Does an Operating System/BIOS Determine Physical Addresses of Devices?
So I understand that in every computer, the Operating System, the BIOS, or both will determine the physical addresses of the hardware devices and then translate that into virtual addresses. What I don'...
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0answers
57 views
Deadlock vs “Progress” requirement of the solution to the critical section problem
I came across following problem:
Consider following code:
...
0
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1answer
42 views
Cache and Main Memory
As we know that average access time is given by
t=p*(tc)+(1-p)*(tc+tm)
where t represent the average time, p is the hit ratio , tc is the time to access the data from the cache and tm is time to ...
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0answers
35 views
How can I implement locking a range of values in a sorted sequence?
I am trying to write a general purpose locking algorithm which allows me to lock a range of contiguous values in a sorted array. To start with, these could be exclusive locks - so two concurrent locks ...
0
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0answers
14 views
Number of memory cycles stolen for transferring one word
The storage area of a disk has the innermost diameter of 10 cm and outermost diameter of 20 cm. The maximum storage density of the disk is 1400 bits/cm. The disk rotates at a speed of 4200 RPM. The ...
1
vote
1answer
56 views
In a kernel, what are “global constructors”?
I am a beginner developing kernels (though I have developed several Hello World programs in C and C++). I frequently see reference being made to global constructors (e.g., osdev https://wiki.osdev.org/...
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2answers
70 views
Why are threads called the unit of dispatch?
Threads called the "unit of dispatch" but what does that mean? I was looking over the web and two operating systems books but I can't find the answer. It seems that processes are defined by two ...
2
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1answer
233 views
How does hashed inverted page table work?
I understand hash function and inverted page table, but then the book I read describes something called hashed inverted page table (use hash to accelerate the finding because IPT is large), with TLB ...
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0answers
23 views
Why is it difficult to differentiate between system and user CPU time?
In the book, Computer Organization and Design, Fifth Edition, by D. Paterson, it is stated that
Differentiating between system and user CPU time is difficult to do
accurately, because it is often ...
