Q. What is an
operating system?
Ans:
The operating
system is a software program that facilitates computer hardware to communicate
and operate with the computer software. It is the most important part of a
computer system without it computer is just like a box.
Q. What are
the different operating systems?
Ans:
- Batched operating systems
- Distributed operating systems
- Timesharing operating systems
- Multi-programmed operating
systems
- Real-time operating systems
Q. What is a
socket?
Ans:
A socket is
used to make connection between two applications. Endpoints of the connection
are called socket.
Q. What is a
real-time system?
Ans:
Real-time
system is used in the case when rigid-time requirements have been placed on the
operation of a processor. It contains a well defined and fixed time
constraints.
Q. What is the
main purpose of an operating system?
Ans:
There are two
main purposes of an operating system:
- It is designed to make sure
that a computer system performs well by managing its computational
activities.
- It provides an environment for
the development and execution of programs.
Q. What is
kernel?
Ans:
Kernel is the
core and most important part of a computer operating system which provides
basic services for all parts of the OS.
Q. Explain the main purpose of an operating
system?
Ans:
Operating
systems exist for two main purposes. One is that it is designed to make sure a
computer system performs well by managing its computational activities. Another
is that it provides an environment for the development and execution of
programs.
Q. What is demand paging?
Ans:
Demand
paging is referred when not all of a process’s pages are in the RAM, then the
OS brings the missing(and required) pages from the disk into the RAM.
Q. What are the advantages of a multiprocessor
system?
Ans:
With
an increased number of processors, there is a considerable increase in
throughput. It can also save more money because they can share resources.
Finally, overall reliability is increased as well.
Q. What is kernel?
Ans:
A
kernel is the core of every operating system. It connects applications to the
actual processing of data. It also manages all communications between software
and hardware components to ensure usability and reliability.
Q. What do you
mean by a process?
Ans:
An executing
program is known as process. There are two types of processes:
- Operating System Processes
- User Processes
Q. What are
the different states of a process?
Ans:
A list of
different states of process:
Ø
New Process
Ø
Running
Process
Ø
Waiting
Process
Ø
Ready Process
Ø
Terminated
Process
Q. What is the
difference between micro kernel and macro kernel?
Ans:
Micro kernel: micro
kernel is the kernel which runs minimal performance affecting services for
operating system. In micro kernel operating system all other operations are
performed by processor.
Macro Kernel: Macro
Kernel is a combination of micro and monolithic kernel.
Q. What is the concept of reentrancy?
Ans:
It is a very
useful memory saving technique that is used for multi-programmed time sharing
systems. It provides functionality that multiple users can share a single copy
of program during the same period.
It has two key
aspects:
- The program code cannot modify
itself.
- The local data for each user
process must be stored separately.
Q. What is the difference between process and
program?
Ans:
A program
while running or executing is known as a process.
Q. What are real-time systems?
Ans:
Real-time
systems are used when rigid time requirements have been placed on the operation
of a processor. It has well defined and fixed time constraints.
Q. What is a virtual memory?
Ans:
Virtual
memory is a memory management technique for letting processes execute outside
of memory. This is very useful especially is an executing program cannot fit in
the physical memory.
Q. Describe the objective of multiprogramming.
Ans:
The
main objective of multiprogramming is to have a process running at all times.
With this design, CPU utilization is said to be maximized.
Q. What is time- sharing system?
Ans:
In
a Time-sharing system, the CPU executes multiple jobs by switching among them,
also known as multitasking. This process happens so fast that users can
interact with each program while it is running.
Q. What is SMP?
Ans:
SMP
is a short form of Symmetric Multi-Processing. It is the most common type of
multiple-processor systems. In this system, each processor runs an identical
copy of the operating system, and these copies communicate with one another as
needed.
Q. How are server systems classified?
Ans:
Server
systems can be classified as either computer-server systems or file server
systems. In the first case, an interface is made available for clients to send
requests to perform an action. In the second case, provisions are available for
clients to create, access and update files.
Q. What is asymmetric clustering?
Ans:
In
asymmetric clustering, a machine is in a state known as hot standby mode where
it does nothing but to monitor the active server. That machine takes the active
server’s role should the server fails.
Q. What is a thread?
Ans:
A
thread is a basic unit of CPU utilization. In general, a thread is composed of
a thread ID, program counter, register set, and the stack.
Q. Briefly explain FCFS.
Ans:
FCFS
stands for First-come, first-served. It is one type of scheduling algorithm. In
this scheme, the process that requests the CPU first is allocated the CPU
first. Implementation is managed by a FIFO queue.
Q. What is RR scheduling algorithm?
Ans:
RR
(round-robin) scheduling algorithm is primarily aimed for time-sharing systems.
A circular queue is a setup in such a way that the CPU scheduler goes around
that queue, allocating CPU to each process for a time interval of up to around
10 to 100 milliseconds.
Q. What are necessary conditions which can
lead to a deadlock situation in a system?
Ans:
Deadlock
situations occur when four conditions occur simultaneously in a system: Mutual
exclusion; Hold and Wait; No preemption; and Circular wait.
Q. Enumerate the different RAID levels.
Ans:
RAID
0 – Non-redundant striping
RAID 1 – Mirrored Disks
RAID 2 – Memory-style error-correcting codes
RAID 3 – Bit-interleaved Parity
RAID 4 – Block-interleaved Parity
RAID 5 – Block-interleaved distributed Parity
RAID 6 – P+Q Redundancy
Q. What is the basic function of paging?
Ans:
Paging
is a memory management scheme that permits the physical address space of a
process to be noncontiguous. It avoids the considerable problem of having to
fit varied sized memory chunks onto the backing store.
Q. What is fragmentation?
Ans:
Fragmentation
is memory wasted. It can be internal if we are dealing with systems that have
fixed-sized allocation units, or external if we are dealing with systems that
have variable-sized allocation units.
Q. How does swapping result in better memory
management?
Ans:
During
regular intervals that are set by the operating system, processes can be copied
from main memory to a backing store, and then copied back later. Swapping
allows more operations to be run that can fit into memory at one time.
Q. What is a socket?
Ans:
A
socket provides a connection between two applications. Each endpoint of a
communication is a socket.
Q. What is Direct Access Method?
Ans:
Direct
Access method is based on a disk model of a file, such that it is viewed as a
numbered sequence of blocks or records. It allows arbitrary blocks to be read
or written. Direct access is advantageous when accessing large amounts of
information.
Q. When does thrashing occur?
Ans:
Thrashing
refers to an instance of high paging activity. This happens when it is spending
more time paging instead of executing.
Q. What is the best page size when designing an
operating system?
Ans:
The
best paging size varies from system to system, so there is no single best when it
comes to page size. There are different factors to consider in order to come up
with a suitable page size, such as page table, paging time, and its effect on
the overall efficiency of the operating system.
Q. When designing the file structure for an operating
system, what attributes are considered?
Ans:
Typically,
the different attributes for a file structure are naming, identifier, supported
file types, and location for the files, size, and level of protection.
Q. What is root partition?
Ans:
Root
partition is where the operating system kernel is located. It also contains
other potentially important system files that are mounted during boot time.
Q. What are device drivers?
Ans:
Device
drivers provide a standard means of representing I/O devices that maybe
manufactured by different companies. This prevents conflicts whenever such
devices are incorporated in a systems unit.
Q. What are the primary functions of VFS?
Ans:
VFS,
or Virtual File System, separate file system generic operations from their
implementation by defining a clean VFS interface. It is based on a
file-representation structure known as vnode, which contains a numerical
designator needed to support network file systems.
Q. What is the purpose of an I/O status
information?
Ans:
I/O
status information provides information about which I/O devices are to be
allocated for a particular process. It also shows which files are opened, and
other I/O device state.
Q. What is multitasking?
Ans:
Multitasking
is the process within an operating system that allows the user to run several
applications at the same time. However, only one application is active at a
time for user interaction, although some applications can run “behind the
scene”.
Q. Explain pros and cons of a command line
interface?
Ans:
A
command line interface allows the user to type in commands that can immediately
provide results. Many seasoned computer users are well accustomed to using the
command line because they find it quicker and simpler.
However,
the main problem with a command line interface is that users have to be
familiar with the commands, including the switches and parameters that come
with it. This is a downside for people who are not fond of memorizing commands.
Q. What is caching?
Ans:
Caching
is the processing of utilizing a region of fast memory for a limited data and
process. A cache memory is usually much efficient because of its high access
speed.
Q. What is spooling?
Ans:
Spooling
is normally associated with printing. When different applications want to send
an output to the printer at the same time, spooling takes all of these print
jobs into a disk file and queues them accordingly to the printer.
Q. What is an Assembler?
Ans:
An
assembler acts as a translator for low-level language. Assembly codes written
using mnemonic commands are translated by the Assembler into machine language.
Q. What are interrupts?
Ans:
Interrupts
are part of a hardware mechanism that sends a notification to the CPU when it
wants to gain access to a particular resource. An interrupt handler receives
this interrupt signal and “tells” the processor to take action based on the
interrupt request.
Q. What is the
difference between internal commands and external commands?
Ans:
Internal
commands are the built-in part of the operating system while external commands
are the separate file programs that are stored in a separate folder or
directory.
Q. What is semaphore?
Ans:
Semaphore is a
protected variable or abstract data type that is used to lock the resource
being used. The value of the semaphore indicates the status of a common
resource.
There are two
types of semaphore:
- Binary semaphores
- Counting semaphores
Q. What is a binary Semaphore?
Ans:
Binary
semaphore takes only 0 and 1 as value and used to implement mutual exclusion
and synchronize concurrent processes.
Q. What is Belady's Anomaly?
Ans:
Belady's
Anomaly is also called FIFO anomaly. Usually, on increasing the number of
frames allocated to a process virtual memory, the process execution is faster,
because fewer page faults occur. Sometimes, the reverse happens, i.e., the
execution time increases even when more frames are allocated to the process.
This is Belady's Anomaly. This is true for certain page reference patterns.
Q. What is starvation in Operating System?
Ans:
Starvation is
Resource management problem. In this problem, a waiting process does not get
the resources it needs for a long time because the resources are being
allocated to other processes.
Q. What is aging in Operating System?
Ans:
Aging is a
technique used to avoid the starvation in resource scheduling system.
Q. What are the advantages of multithreaded
programming?
Ans:
A list of
advantages of multithreaded programming:
Ø
Enhance the
responsiveness to the users.
Ø
Resource
sharing within the process.
Ø
Economical
Ø
Completely
utilize the multiprocessing architecture.
Q. What are
overlays?
Ans:
Overlays makes
a process to be larger than the amount of memory allocated to it. It ensures
that only important instructions and data at any given time are kept in memory.
Q. When does trashing occur?
Ans:
Thrashing
specifies an instance of high paging activity. This happens when it is spending
more time paging instead of executing.
Q. What is GUI?
Ans:
GUI
is short for Graphical User Interface. It provides users with an interface
wherein actions can be performed by interacting with icons and graphical
symbols. People find it easier to interact with the computer when in a GUI
especially when using the mouse. Instead of having to remember and type
commands, users click on buttons to perform a process.
Q. What is preemptive multitasking?
Ans:
Preemptive
multitasking allows an operating system to switch between software programs.
This, in turn, allows multiple programs to run without necessarily taking
complete control over the processor and resulting in system crashes.
Q. Why partitioning and formatting is a
prerequisite to installing an operating system?
Ans:
Partitioning
and formatting create a preparatory environment on the drive so that the
operating system can be copied and installed properly. This includes allocating
space on the drive, designating a drive name, determining and creating the
appropriate file system and structure.
Q. What is plumbing/piping?
Ans:
It
is the process of using the output of one program as an input to another. For
example, instead of sending the listing of a folder or drive to the main
screen, it can be piped and sent to a file, or sent to the printer to produce a
hard copy.
Q. What is NOS?
Ans:
NOS
is short for Network Operating System. It is a specialized software that will
allow a computer to communicate with other devices over the network, including
file/folder sharing.
Q. Differentiate internal commands from
external commands.
Ans:
Internal
commands are built-in commands that are already part of the operating system.
External commands are separate file programs that are stored in a separate
folder or directory.
Q. What is
monolithic kernel?
Ans:
A monolithic
kernel is a kernel which includes all operating system code is in single
executable image.
Q. What is the
use of paging in operating system?
Ans:
Paging is used
to solve the external fragmentation problem in operating system. This technique
ensures that the data you need is available as quickly as possible.
Q. What is the concept of demand paging?
Ans:
Demand paging
specifies that if an area of memory is not currently being used, it is swapped
to disk to make room for an application's need.
Q. What is the advantage of a multiprocessor
system?
Ans:
As many as
processors are increased, you will get the considerable increment in
throughput. It is cost effective also because they can share resources. So, the
overall reliability increases.
Q. What is virtual memory?
Ans:
Virtual memory
is a very useful memory management technique which enables processes to execute
outside of memory. This technique is especially used when an executing program
cannot fit in the physical memory.
Q. What is thrashing?
Ans:
Thrashing is a
phenomenon in virtual memory scheme when the processor spends most of its time
in swapping pages, rather than executing instructions.
Q. What are the four necessary and sufficient
conditions behind the deadlock?
Ans:
These are the
4 conditions:
1) Mutual
Exclusion Condition: It specifies that the resources involved are non-sharable.
2) Hold
and Wait Condition: It specifies that there must be a process that is
holding a resource already allocated to it while waiting for additional
resource that are currently being held by other processes.
3) No-Preemptive
Condition: Resources cannot be taken away while they are being used by
processes.
4) Circular
Wait Condition: It is an explanation of the second condition. It specifies
that the processes in the system form a circular list or a chain where each
process in the chain is waiting for a resource held by next process in the
chain.
Q. What is a thread?
Ans:
A thread is a
basic unit of CPU utilization. It consists of a thread ID, program counter,
register set and a stack.
Q. What is FCFS?
Ans:
FCFS stands
for First Come, First Served. It is a type of scheduling algorithm. In this
scheme, if a process requests the CPU first, it is allocated to the CPU first.
Its implementation is managed by a FIFO queue.
Q. What is SMP?
Ans:
SMP stands for
Symmetric MultiProcessing. It is the most common type of multiple processor
system. In SMP, each processor runs an identical copy of the operating system,
and these copies communicate with one another when required.
Q. What is RAID? What are the different RAID
levels?
Ans:
RAID stands
for Redundant Array of Independent Disks. It is used to store the same data
redundantly to improve the overall performance.
Following are
the different RAID levels:
RAID 0 -
Stripped Disk Array without fault tolerance
RAID 1 -
Mirroring and duplexing
RAID 2 - Memory-style
error-correcting codes
RAID 3 -
Bit-interleaved Parity
RAID 4 -
Block-interleaved Parity
RAID 5 -
Block-interleaved distributed Parity
RAID 6 - P+Q
Redundancy
Q. What is deadlock? Explain.
Ans:
Deadlock is a
specific situation or condition where two processes are waiting for each other
to complete so that they can start. But this situation causes hang for both of
them.
Q. Which are the necessary conditions to
achieve a deadlock?
Ans:
There are 4
necessary conditions to achieve a deadlock:
- Mutual Exclusion: At least one resource
must be held in a non-sharable mode. If any other process requests this
resource, then that process must wait for the resource to be released.
- Hold and Wait: A process must be
simultaneously holding at least one resource and waiting for at least one
resource that is currently being held by some other process.
- No preemption: Once a process is holding
a resource ( i.e. once its request has been granted ), then that resource
cannot be taken away from that process until the process voluntarily
releases it.
- Circular Wait: A set of processes { P0,
P1, P2, . . ., PN } must exist such that every P[ i ] is waiting for P[ (
i + 1 ) % ( N + 1 ) ].
Q. What is
Banker's algorithm?
Ans:
Banker's
algorithm is used to avoid deadlock. It is the one of deadlock-avoidance
method. It is named as Banker's algorithm on the banking system where bank
never allocates available cash in such a manner that it can no longer satisfy
the requirements of all of its customers.
Q. What is the difference between logical
address space and physical address space?
Ans:
Logical
address space specifies the address that is generated by CPU. On the other hand
physical address space specifies the address that is seen by the memory unit.
Q. What is fragmentation?
Ans:
Fragmentation
is a phenomenon of memory wastage. It reduces the capacity and performance
because space is used inefficiently.
Q. How many types of fragmentation occur in
Operating System?
Ans:
There are two
types of fragmentation:
- Internal fragmentation: It is occurred when we deal
with the systems that have fixed size allocation units.
- External fragmentation: It is occurred when we deal
with systems that have variable-size allocation units.
Q. What is spooling?
Ans:
Spooling is a
process in which data is temporarily gathered to be used and executed by a
device, program or the system. It is associated with printing. When different
applications send output to the printer at the same time, spooling keeps these
all jobs into a disk file and queues them accordingly to the printer.
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Good questions
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