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In the MCQ of UGC net examinations computer science i found these answer options see the attachmentQuestions number 57 confused with the modes
A processor can execute in various modes as a protection mechanism. Every processor I am aware of has at least User (lowest protection) and Kernel (highest protection) modes. Some processors have additional modes in between those two. For example, the VAX processor has Supervisor Mode (where command interpreters reside) and Executive Mode (where the record management services reside).
A signal handler executes in User Mode. You should go right to that.
Kernel mode is the most possible alternative answer. However, signal handlers do not execute in kernel mode.If they did, users could write programs that could compromise security and system integrity.
Privileged Mode and Superuser Mode are fillers; pure inventions that cannot possibly be correct.
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I was reading operating system concepts by Silberschatz and i came across
"Some operating systems include the command interpreter in the kernel"
statement.
I cannot understand how such an arrangement will be implemented. also if you cn give some examples of os which provide such arrangement.
Thank you for taking time to help.
Some operating systems do this, like vxWorks. It's just taking the shell itself, and packing it into the kernel. If you can do something in user space (ie: shell as a user space application), you can do it (with some difficulty) in the kernel. The usual caveats apply, such as not being able to link user space libraries into kernel code, etc.
It's easy, on Linux for example, to write directly to a PTY from a kernel module. You can just as easily get the stdin for a process by hijacking system calls, among other methods. Now you have your I/O mechanisms, and just need a parser to handle all the internal logic.
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Scenario:
Task Scheduler - puts a system to a sleep
Task Scheduler - wakes the
system up
Task Scheduler - launches another program but it is vital
that it was
Problem:
During the wake up procedure, a system state stops at the window namely "Lock Screen" which shows time and it cannot really run tasks I want after the system's wake up.
To deal with the Lock Screen, I usually do the following:
Press Enter -> takes me to user account selection window
Press Enter again -> having one account and no password -> takes me
to desktop.
My thoughts so far:
Perhaps I could execute some script which would help me send "Enter" command as input to these two states, yet, I have no clue how to do that.
Relevant to some extent resources found by far:
How to perform keystroke inside powershell?
Put computer in standby after running a scheduled task but only if it had to wake up to run it
If there are suggestions or other ideas on how to go around this Lock and User Account screens, I am grateful if you share it!
Thank you!
You can set autologon up so it logs directly in to the desktop.
You really need to only setup three registry keys.
I've included a link to the tech net page
https://support.microsoft.com/en-us/kb/324737
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Can anyone help in making me understand, what's the real difference between chroot command and chroot() system call.
A system call is a means for a program to interact with the kernel.
A unix tool command is either a small stand alone program (in this case) or else a shell built in (in some other cases). This allows a user or a script to perform operations without having to provide low level program code for doing so.
Where a command and a system call have the same name, typically the command provides a way to accomplish the functionality of the system call, or something similar.
System calls are documented in section 2 of the manual, while commands may be elsewhere such as page 8. So if you type
man 2 chroot you will get the documentation for the system call
and if you type
man 8 chroot (or in many cases simply fail to specify a page) you will get the documentation for the command.
if you type
which chroot you will find the location of the executable which implements the command, assuming it is in your search path as it usually would be.
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The question actually is :
If I have some processor named x
I have 3 Operating Systems named a,b,c
Now how can I decide that which operating system controls the processor ?
What is the basic understanding between the processor and Operating system ?
And the above 3 operating systems are not of different versions from same company..
To be specific how Android hardware is different from iPhone hardware and why can't iOS be installed on Android hardware...??
Thanking you..
You are actually asking a question which shows your lack of understanding of OS, CPU and other technical terminologies.
Actually, You need to study the basic of Os and CPU to get a deep understanding on the topic. But, I will definitely help you out by defining both the terminologies.
Your computer's operating system has two main objectives in its management of the central processing unit, or CPU. First, the OS makes sure that as many processor cycles are used for work as possible.
Second, the OS schedules the processor's attention among the demands of different processes. Processes are actions that can be controlled and are the basic units of software with which the OS communicates. A process may be a task, such as a virus check, that runs in the background so you never even know it's working. It also may be one of several tasks that an application, such as a spreadsheet, executes at your request. In a multitasking OS, the OS has to switch the processor's attention between competing processes many times per second because the processor can only do one thing at a time.
Briefly summarizing :
A processor is the 'engine' of the computer - it runs all the software and moves data around. The best processor in general has more cores (core i7), and a higher speed.
An operating system is the 'traffic cop' of all the software on the computer - it's software that controls how all the other programs on the computer work together and share the resources of the computer.
Hope you have got an idea :)
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We need to simulate an unstable network connection to try to debug some connectivity issues in our server/client application and I was wondering if there are any programs out there that can simulate those conditions such as on a faint wireless network.
I'm not just referring to reducing bandwidth, but also reducing reliability, frequent on and off, short bursts of disconnectedness, etc.
I used a tool called netem that runs on linux. It allows you to increase packet loss at a given percentage, introduce delays within packets and handle packet re-ordering. Basically it's designed to emulate different networks.
All you need to get it up and running is a spare machine to install Linux on with a couple of Ethernet cards. Hook it up as a bridge, and run netem between them. Should be quite simple to do. I used it for my University project having no Linux experience, but I've probably still got all the setup instructions somewhere.
Ian's solution seems like a pretty good long term solution, but sounded a little involved for just some quick testing. (finding another machine, hooking it up, possibly setting up router stuff etc)
I ended up just using Net Limiter and randomly set the limit to something stupidly low manually (like 1 byte/sec) and that seems to be sufficient for our needs.
http://snad.ncsl.nist.gov/nistnet/
It's a little complicated to setup, but works very well.