OS Basics
What is a block device?
A device providing access to raw bytes
What is the difference between a concurrent system and a parallel system?
A concurrent system runs multiple processes together (in turn) a parallel system runs multiple processes at the same time in separate paths.
What is the worst case scenario if an Operating System does not apply some kind of load-balancing
A processes are assigned to a single core making the system effectively a single-core system.
Output redirection uses what symbol?
>
If the time quantum get too large, RR scheduling degenerates to _______?
FCFS
Which of the following scheduling algorithm may suffer from convoy efect?
FCFS
the current directory
may be included in the search path
Choose the absolute path
C:\users\uname
What is RamDisk?
Storage implemented in volatile memory
A file system takes up storage space
True
What is the backing store named in Windows?
pagefile.sys
What is the duty of the boot block?
Provides the necessary information to begin loading an operating system
What parameter can be used to reduce the results to a smaller set?
-filter
Which block houses the MBR
0
A CPU has four cores, each running at 1GHz. A single process is running. What will the effective processing speed of that process be?
1 GHz
A single core CPU, running at 1 GHz, system has 5 processes executing. What would the system speed be running at (in GHz)?
1 GHz
Assume that value of the base and limit registers are 1200 and 350 respectively. Which of the following addresses is legal?
1200
How many total unique values can be represented with 4 bits?
16
A single core CPU system running at 1 GHz has 5 processes executing. What would be the effective processing speed (in GHz) of each process?
200 MHz
Given a standard block size of 4KB, how many blocks would a 10 KB file require in storage?
3
What is the value of the number 3 when encoded in binary?
3
Which block houses the Partition Table in GPT?
3
A CPU has four cores, each running at 1 GHz. Currently, three processes are running on the system. Assuming no blocking, what would be the total processing speed, in GHz, of the system?
3 GHz
What is the standard block size now?
4 KB
RAID level ____ is the most common parity RAID system.
5
What is the purpose of the Process Control Block?
A Kernel data structure used by the Kernel to track and manage a process.
What best describes a thread pool
A container of multiple, ready, threads handed out to processes for processing an a per-request basis.
What is a socket?
A form of client/server communication that designates a channel between end points
What is a volume?
A logical drive derived from one or more partitions and formatted with a file system
Interrupt
A mechanism for signaling to the the CPU to switch out the current running process
What is an interrupt?
A message to the Operating system that something has happened most likely causing a context shift.
What is a logical address?
A method where the CPU uses a Shorthand (usually an offset) rather than physical addresses
Paging moves ____ to/from Main Memory from/to the Backing Store.
A page
Child processes inherit UNIX ordinary pipes from their parent process because:
A pipe is treated as a file descriptor and child processes inherit open file descriptors from their parents.
Client/Server
A process request a resource using a message and receives a message in return
What is the best description of and API
A series of defined functions interfacing into a library of subroutines that allow any application to make use of the functionality in the library simply through implementing and using the functions defined.
What is a major benefit of Memory-mapped I/O?
A single instruction can support the movement of many bytes processed in I/O
What is a directory?
A special system file that contains a table pointing to other files
Describe an interrupt
A system resource becomes available or unavailable, it sends a signal to the operating system of this fact. The CPU sees the interrupt and promptly moves to interrupt handling which involves switching out the current process from the CPU and switching in the next process in line for CPU usage
What is the $_ symbol in a command?
An instance variable referring to the last object in the pipeline
What is the word as far as the Operating System is concerned?
A unit of bytes matching the size of the register used by the CPU
What is a significant benefit of DMA
Ability of devices to interact without supervision by CPU
What is the purpose of Logical Block Addressing?
Abstracts all storage media into a contiguous array of bytes
Computing system need cache because
Accessing main memory is slow and cache speeds it up
In memory-mapped I/O
Address space of the computing device is used for communicating with the I/O devices using the standard I/O instructions.
Which of the following can be a solution to the problem of indefinite blockage of low priority processes?
Aging
which of the following is FALSE about Storage Area Networks?
Allocation of storage to hosts is static
Advantages of paging?
Allows processes to use non contiguous memory Eliminates memory fragmentation
Which of the following is true?
An I/O-bound process is one that spends more of its time doing I/O than it spends doing computations
Process
An encapsulation of code for execution in the CPU
What is an ISO image?
An operating system stored in a file under ISO 9660 formatting
To count the number of files, what command do you pipe the get-childitem command results to?
measure-object
Which command will connect to the standard output of the job and display it on the screeen?
receive-job
Which command will display information about job 3 and only job 3?
receive-job -id 3
The stack is a stack of data structures containing execution information and temporary variables. What is the name of the data structure pushed and popped from the stack?
Frame
What is the difference between NAS and SAN?
SAN is its own network of storage devices while NAS is just storage devices attached to the network.
a relative path name defines a path from
the current directory
Which of the following refers to the capability to allow multiple tasks make progress on a shingle processor system?
Concurrency
What is the difference between buffers and caches
Buffers store data for reception/transmission, caches store redundant data for performance improvement.
What are the primary cause of context shifts?
Bursts of I/O operations
What is the first step in the boot load process?
BIOS or UEFI finds the drive flagged as bootable.
Once the BIOS/UEFI has found the bootable drive, what happens in the boot process?
BIOS/UEFI loads bootloader into memory and stars it.
What is a spooler?
Basically a type of send buffer often used for printing.
Why is it hard to update a Monolithic Kernel
Because everything is compiled into a single binary. To change it you must recompile the entire Kernel.
I/O bound program typically has many short ______ and a CPU bound program might have a few long _______
CPU burst, CPU burst
Which of the following selects from among the processes that are in the ready queue to execute and allocate the CPU to one of them?
CPU scheduler
Data
Contains static data for the program determined at compile time
How does polling work?
Continually request update from a device
What is the purpose of environment variables?
Creates an indirect layer between and application and the operating system so that resources can vary across systems
Heap
Data structure for tracking long lived values. A type of tree structure.
Stack
Data structure for tracking temporary values and execution. First in first out
What is the function of a partition table?
Defines the start and end of partitions on the storage device as well as whether or not the drive is bootable
Which command will list all of the files in the directory in windows?
Dir ls
How does a File Control Block point to the actual file data?
Direct and indirect blocks
which of the following technology reduces the overhead for bulk data movement?
Direct memory access
The option which an embedded system cannot handle
Dynamic swapping of hardware.
What is the purpose of load balancing?
Evenly distribute jobs across all cores
PowerShell is case sensitive?
False
What scheduling is most susceptible to Head-of-the-line blocking?
Fist-come First-Server
Why are processes necessary for an Operating System?
For scheduling CPU time for specific task.
Which of the following cases could force a process removed from the CPU?
Fork a child Interrupt or time slice expired I/O request
Why is it possible for multiple programs, under a paging paradigm, to share the same pages of memory?
Frames are logically separated from pages and thus the MMU can map any page to any gram as it sees fit.
What does get-item do?
Gets the values for a specified attribute or set of attributes
Hard Disk Drives locate data on a disk internally using a geometry based metric consisting of what three components?
Head sector cylinder
Which of the following contains dynamically allocated data during program run time?
Heap section
Which of the following will trigger and interrupt?
I/O completion
Why is the Process space so tightly defined?
Provide a means for the Operating System to manage the process and know its size Provide independence between processes (boundaries)
In order to load an operating system, the operating system must exist. What do we tend to call the structure used to house the Operating System and file structure.
Image
Why is scheduling important for I/O?
Improved performance
Which of the following stage triggers the CPU switch from user program to interrupt processing?
Interrupt signaled
Which of the following contains the addresses of all the service routines?
Interrupt vector
In what way is an operating system like a government?
It creates an environment within which other programs can do useful work.
what is the purpose of the System Bus?
It provides a line of communication between the CPU and all system compoonents
Which of the following programs runs all the time on the computer?
Kernel
For every process using user space threads there must exist at least one _______ in order to use threading
Kernel thread
What is the primary benefit of threading model?
Less overhead
Which of the following statement is correct?
Limit register hold the size of a process
Monolithic Kernel
Loads all necessary utilities and drivers into a single binary file. Easy to implement, cannot be changed while running.
What represents functions that an Operating System perform
Manage drivers and access to resources Manage access to the System Manage Processes running on the system
What is memory fragmentation?
Memory clutter as a result of allocation and de allocating memory
what are file attributes?
Meta-data concerning files
What does the TLB do
Provides a hardware caching mechanism for the page table
What is the purpose of Modules?
Modules allow some indirection in the kernel so that the module can be modified without the need to modify the kernel
A page out operation
Moves a page from memory to the backing store.
Shared memory
Multiple processes have access to the same region in memory and can read and update this region
What is the problem of shared memory?
One process might overwrite the changes of another process
Which of the following is a method for implicit threading?
OpenMP Grand central dispatch thread pools
What scheduling algorithm allows for differentiated services similar to Quality of Service in networks?
Priority Scheduling
Which best illustrates the difference between Threads and Processes?
Processes are heavyweight while Threads are lightweight
Message Passing
Processes subscribe to and publish messages. These messages are used to communicate state.
Linux permissions are designated by rwx what do those stand for?
Read, write, execute
A process is in the ready queue. What state is the process in?
Ready
Which of the following process state will be switched from "running" state when an interrupt occurs?
Ready
The list of processes waiting to execute on a CPU is called a
Ready queue
What does the replace command do?
Replaces characters in the text
Which of the following criteria is more important for an interactive system?
Response time
Which of the following benefits go to multithreaded programming?
Responsiveness Resource sharing economy scalability
What does the get-member function do?
Returns a list of all attributes available for a given object.
Which scheduling algorithm makes use of a time quantum?
Round-Robin
A process is executing in the CPU. What state is the process in?
Running
When a thread has completed its work, what happens next?
The tread joins with the thread that spawned it.
Which of the following scheduling algorithms gives the minimum average waiting time for a given set of processes?
SJF
a partition does which of the following?
Sections the physical storage media
Which of the following items does not belong to the function of a dispatcher?
Selecting a process among the available ones in the ready queue
How do interrupts work?
Send a signal to the CPU to signify device state has changed
What scheduling algorithm guarantees a minimum average wait time, but in practices can only be implemented as an approximation.
Shortest-Job First
What does tee-object do?
Splits the output stream into 2 output streams.
What things are contained in the Kernel space
Structures to track User Application execution Structures to track system resources and connect to hardware
What must an Operating System be capable of prior to even considering real time scheduling?
Sufficient time precision
What does the boot loader do?
The boot loader finds the next boot loader or operating system chunk and loads it into main memory. At completion, it executes what is has loaded.
What is the idea behind demand paging?
The entire program need not exist in memory-- only the parts used.
System Bus
The interconnecting pathways of various system resources for a system
what is the working set?
The set of data and instructions used by a process
File system
The structure and metadata for storing files and data
What is root?
The topmost directory on a particular drive
Which of the following statements regarding solid state disks is false?
They generally consume more power than traditional hard disks
The operating system must atomize resources and hand them out like currency. Which choice represents how the operating system atomizes CPU time for processes?
Time slices
Why might an Operating System what to use Processor or Core Affinity?
To improve caching efficiency
Get-childitem can recursively exam directories using the -r option.
True
The operating system maintains Tables of open files
True
Which of the following criteria is more important from the point of view of a particular process?
Turnaround time
Which of the following models are possible for the relationship between the user threads and kernel threads?
Two-level model one-to-one model many-to-one model many-to-many model
some binary files can include a magic number. This mechanism is used by
UNIX
The ready queue can be implemented as a ____
Unordered linked list FIFO Queue tree priority queue
The two separate modes of operation in the system are
User mode and kernel mode
A process is blocked on IO. What state is the process likely in?
Waiting
What is a context shift?
When the operating system ceases execution of a process, returns to Kernel space, performs admin duties, and then picks the next process to execute and moves to that process's user space.
What wmiobject class will return information about the page file?
Win32_PageFileUsage
code
contains the actual instructions of the program
What are the two primary file operations?
Write Read
if a page has the modify bit set it will be written to virtual memory if it is evicted from physical memory?
Yes
what command would show the number of maps per second?
\cache\data maps/sec
register
a memory tool used by CPU for calculations and processing data
in a multithreaded server architecture, which of the following is used to service a new user request?
a new created thread
In demand paging,
a page is loaded in memory only when it in needed during execution.
An advantage of virtual memory is that
a program can be much larger than the size of physical memory. the programmers can concentrate programming the problem instead of worrying about the amount of physical memory available. it provides a way to execute a program that is only partially loaded in memory
swapping moves ___________ from/to main memory to/from the Backing Store.
an entire process
Compared to USB, NVMe provides
both higher throughput and lower latency.
Technique used to improve I/O efficiency by temporarily storing copies of data is called
caching
Which command will show the contents of a file named myfile.txt when the file is in the directory C:\User\vv\test and the current working directory is C:\users\vv
cat test\myfile.txt
Which command will change the directory form C:\Users\uname to C:\Users?
cd ..
Which of the following items are shared across multiple threads belonging to the same process?
code, data, files
Buffering in I/O is used to do which of the following
cope with a speed mismatch between the producer and consumer of a data system provide adaptions for devices that have different data-transfer sizes support copy semantics for application I/O
Which of the following contains global data?
data section
What is it called when two threads each want a resource, but the desired resource is owned by the other tread
deadlock
Which command will redirect the text from echo to file named "redirect.txt"
echo "here is some text" > "redirect.txt"
Which command will create a file named newfile.txt in the directory C:\Users\vv\test when the current working directory is C:\users\vv
echo "some text into my new file!" > test\newfile.txt
Which refers to a physical block of memory in main memory?
frame
Available frames that can hold a memory page in main memory are managed in what?
free-frame list
Which command will count all of the Archive files in the current directory only?
get-childitem -At A -file
Which object will give information about total and available physical memory?
get-computerinto
Which command will list all storage devices connected to a comoputer?
get-disk
Which command will get all partitions for disk 1?
get-partition -disknumber 1
Which command will show all of the volumes connected too the computer?
get-volume
Which command will show clock speed and speed of the RAM?
get-wmiobject -class WIn32_PhysicalMemory
File's ____ is a unique tag identifies the file within the file system
identifier
Where is the location of L1 cache
inside CPU core
Hybrid Kernel
introduces the idea of modules so that it is possible to update portions of the kernel without needing to recompile the while kernel. Typically considered the best of both worlds approach.
A free-frame list
is a set of all frames that are currently unallocated to any process
Which of the following principles is used for adding and removing items for a stack?
last in first out
Which of the following data structure is used to manage the processes in Linux?
linked list
Micro Kernel
loads in the minimum amount of services into the Kernel for function and places anything else into user space. very dynamic but high overhead
An address generated by a CPU is referred to as a _____?
logical address
The _____ model multiplexes many user-level threads to a smaller or equal number of kernel threads
many-to-many
The page table ___
maps logical memory to physical memory
to further optimize I/O performance, some SSD schedulers
merge adjacent write requests but not adjacent read requests
Which command will create a directory named newtest in the directory C:\Users\vv\test when the current working directory is C:\users\vv
mkdir C:\users\vv\newtest mkdir test\newtest
The ___ model maps each user-level thread to one kernel thread.
one-to-one
Which refers to a logical block of memory used by the CPU?
page
the mechanism used by the Operating System to determine that a memory page does not exist in main memory is called what?
page fault
In polling I/O, the main inefficiency comes from
polling when it is attempted repeatedly yet rarely finds a device ready for service
Component that measures elapsed time and to trigger operations is called a
programmable interval timer
What would be the proper chain of events to sort processes in ascending order and list just the smallest 10?
ps | sort cpu | select -f 10
Which of the following computing environments place rigid time requirements on the operation of a processor or the flow of data?
real-time embedded system
What command do you use to get the data from a psjob that is running?
receive-job
Which command will delete a job?
remove-job
What does the substring command do?
returns a portion of the original text
Which command will remove a file names "myfile.txt" when the file is in the C:\Users\vv\test and the current working directory is c:\Users\vv
rm test\myfile.txt
Which PSJobs command will start a job to execute ls in your home directory?
start-job -scriptblock {ls ~}
A significant problem with priority scheduling algorithms is _____
starvation
Which of the following contains the executable code?
text section
A sign of thrashing is
the CPU utilization decreases as the degree of multiprogramming is increased.
In a blocking system call, the execution of a process is suspended
the I/O has completed
What happens if the free-frame list is empty when a page is requested that does not exist in main memory?
the Page replacement algorithm activates
Reentrant code is easier to share when paging is used, because?
the code doesn't change during execution
What is thrashing when referenced in the context of virtual memory?
the free-list has become exhausted causing page faults to grow rapidly.
Anonymous memory of a process refers to
the pages not associated with the binary executable file of the process
Why does the operating system split the memory into Kernel space and user space?
to isolate the resources needed by the operating system from those used by applications
What class is used to get information about the Logical Cores?
win32_perfformatteddata_perfos_processor
What wmiobject class shows information on processes?
win32_process
What is the biggest weakness of Solid State media?
write limits
Piping uses what symbol?
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