Operating Systems Job Interview Questions and Answers: The Ultimate Guide

Table of Contents

What do you mean by operating system? What are its basic functions?

An operating system (OS) is basically a software program that manages and handles all the resources of a computer, such as hardware and software. The first operating system was introduced in the early 1950s and was called GMO. The operating system is responsible for managing, processing, and coordinating overall activities and the sharing of computer resources. It acts as an intermediary between the computer and the user of the computer hardware.

Features of the operating system: The features of
the operating system are numerous. Some of the important features of the operating system are as follows:

Memory and processor management
Provide users with a user interface
File management and device management
Scheduling of resources and jobs
Error detection
safe

A collection of basic operating system interview questions and answers

Why is the operating system important?

Analysis of Operating System Interview Questions: The operating system is the most important and important part of a computer, without it, it is considered useless. It enables an interface or acts as a link between the interaction between the computer software installed on the operating system and the user. It also helps in communicating with the hardware and maintaining a balance between the hardware and the CPU. It also provides users with a platform for services and programs to run. It performs all the common tasks that are required for the application.

What are the common interview questions for operating systems: What is the main purpose of an operating system? What are the different types of operating systems?

The main purpose of an operating system is to execute user programs that make it easier for users to understand and interact with the computer as well as run applications. It is specifically designed to ensure better performance of computer systems by managing all computing activities. It also manages computer memory, processes, and operations for all hardware and software.

Operating System Type:

Batch operating systems (e.g., payroll systems, transaction processes, etc.)
Multi-program operating systems (e.g. Windows O/S, UNIX O/S, etc.)
Time-sharing operating systems (e.g. Multics, etc.)
Distributed operating systems (LOCUS, etc.)
Real-time operating systems (PSOS, VRTX, etc.)

What are the benefits of a multiprocessor system?

A multiprocessor system is a system that contains two or more CPUs. It involves working on different computer programs at the same time and is mostly carried out by computer systems that have two or more CPUs that share a single memory.

Benefits::

Nowadays, such systems are widely used to improve the performance of systems that run multiple programs at the same time.
By increasing the number of processors, more tasks can be completed per unit of time.
Since all processors share the same resources, the throughput is also significantly increased and is cost-effective.
It simply improves the reliability of the computer system.

What is the RAID structure in the OS? What are the different levels of RAID configurations?

RAID (Redundant Arrays of Independent Disks) is a method used to store data on multiple hard disks, so it is considered to be a data storage virtualization technology that combines multiple hard disks together. It simply balances data protection, system performance, storage space, and more to improve the overall performance and reliability of your data storage. It also increases the storage capacity of the system, the main purpose of which is to achieve data redundancy to reduce data loss.

Different levels of RAID Nowadays, there are various schemes

or levels of RAID as follows:

RAID 0 – Non-redundant striping: This level is used to improve the performance of the server.
RAID 1 – Mirroring and Duplex: This level, also known as disk mirroring, is considered the easiest way to achieve fault tolerance.
RAID 2 – In-Memory Error Correction Codes: This level typically uses a dedicated Hamming code parity, which is a linear form of error correction code.
RAID 3 – Bit Interleaved Parity: This level requires a dedicated parity drive to store parity information.
RAID 4 – Block Interleaved Parity: This level is similar to RAID 5, but the only difference is that this level restricts all parity data to a single drive.
RAID 5 – Block Interleaved Distributed Parity: This level provides far better performance than disk mirroring and fault tolerance.
RAID 6 – P+Q redundancy: This level typically provides fault tolerance for two drive failures.

What is a graphical user interface?

A GUI (Graphical User Interface) is basically a user interface that allows users to interact with the operating system using graphics. The GUI was created because it is more user-friendly, simpler, and easier to understand than the command-line interface. Its main goal is to improve efficiency and ease of use. Users don’t need to memorize the commands and simply follow the process with the click of a button. Examples of GUIs include Microsoft Windows, macOS, Apple’s iOS, and more.

What is plumbing and when is it used?

A pipeline is typically a connection between two or more interrelated processes. It is a mechanism for inter-process communication using messaging. One can use pipelines to easily send information such as the output of one program process to another. It can be used when two processes want to communicate in one way, i.e., inter-process communication (IPC).

What are the different types of operations that semaphores can do?

There are basically two possible atomic operations:

Wait()
Signal()

What is a bootloader in an operating system?

It is usually a program that initializes the operating system during boot, i.e. the first code that is executed whenever a computer system boots. The operating system is loaded through a boot process or a program commonly known as bootloading. The entire operating system relies solely on the bootloader to perform and function properly. It is stored entirely in a boot block in a fixed location on disk. It also locates the kernel and loads it into the main memory, after which the program begins to execute.

Explain the need for pagination?

On-demand pagination is a method of loading pages into memory on demand. This method is mostly used for virtual memory. In this case, the page is only brought into memory if the location on that particular page is referenced during execution. The following steps are generally followed:

Try to access the page.
If the page is valid (in memory), the instruction continues to be processed normally.
If the page is invalid, a page fault trap occurs.
Check if the memory reference is a valid reference to a location on secondary memory. If not, the process is terminated (illegal memory access). Otherwise, we have to do pagination in the desired page.
Schedule disk operations to read the desired pages into main memory.
Restart the instruction that was interrupted by the operating system trap.

What does RTOS mean?

A real-time operating system (RTOS) is an operating system for real-time applications, i.e., those applications where data processing should be done within a fixed small measure of time. It performs much better for tasks that need to be performed in a short period of time. It is also responsible for executing, monitoring, and taking full control of the process. It also takes up less memory and consumes fewer resources.

Types of RTOS:

Hard Real-Time
Firm Real-Time
Soft Real-Time

RTOS are used in air traffic control systems, anti-lock braking systems, and pacemakers.

What does process synchronization mean?

Process synchronization is basically a method of coordinating processes that use shared resources or data. It’s important to ensure that collaboration processes are executed synchronously to maintain data consistency. Its main purpose is to use mutexes to share resources without any interference. There are two types of process synchronization:

Stand-alone process
Collaborative process

What is IPC? What are the different IPC mechanisms?

IPC (Inter-Process Communication) is a mechanism that requires the use of resources, such as memory shared between processes or threads. With IPC, the operating system allows different processes to communicate with each other. It is only used to exchange data between multiple threads in one or more programs or processes. In this mechanism, different processes can communicate with each other through the approval of the operating system.

Different IPC mechanisms:

pipeline
Message queues
Semaphore
socket
Shared memory
Signal

What are the common interview questions for operating systems: what is the difference between primary memory and secondary memory?

Main Memory: The main memory in a computer is RAM (Random Access Memory). It is also known as main memory or read-write memory or internal memory. The programs and data that the CPU needs during program execution are stored in that memory.
Secondary memory: Secondary memory in a computer is a storage device that can store data and programs. It is also known as external memory or additional memory or backup memory or secondary memory. This type of storage device is capable of storing large amounts of data. The storage device can be a hard drive, a USB flash drive, a CD, etc.

Main memory	Secondary memory
The processing unit has direct access to the data.	First, the data is transferred to the main memory and then routed to the processing unit.
It can be both volatile and non-volatile in nature.	It is non-volatile in nature.
It costs more than secondary memory.	It is more cost-effective or less cost-effective than main memory.
It is ephemeral because the data is stored temporarily.	It is permanent because the data is stored permanently.
In this memory, data is lost whenever a power failure occurs.	In this memory, data is stored permanently, so it is not lost even in the event of a power failure.
It is much faster than secondary memory and can save the data that your computer is currently using.	It is slower as compared to the main memory and saves different types of data in different formats.
It can be accessed through data.	It can be accessed through I/O channels.

What does overlays mean in OS?

Operating System Interview Questions Analysis: Overlays is basically a programming method that divides a process into parts so that important and needed instructions are kept in memory. It doesn’t require any kind of support from the operating system. By keeping only the important data and instructions that may be needed at any given time, it can run programs that are larger than physical memory.

Write out the top 10 operating system examples?

Some of the most commonly used top operating systems are given below:

MS-Windows
Ubuntu
Mac OS
Fedora
Solaris
Free BSD
Chrome OS
CentOS
Debian
Android

Intermediate Operating Systems Interview Questions and Answers Collection

What is virtual memory?

It is a technical feature of memory management of the operating system, which gives the user the illusion of very large (main) memory. It is simply a space to store a larger number of programs on its own in the form of pages. It allows us to increase the use of physical memory through the use of disks, and it also allows us to carry out memory protection. It can be managed by the operating system in two common ways, namely paging and segmentation. It acts as temporary memory that can be used along with RAM for computer processes.

What is a thread in an operating system?

A thread is an execution path that consists of a program counter, a thread ID, a stack, and a set of registers within a process. It is the basic unit of CPU utilization, which makes communication more effective and efficient, enables the utilization of multiprocessor architectures on a larger scale and more efficiently, and reduces the time required for context switching. It simply provides a way to improve and enhance the performance of the application through parallelism. Threads are sometimes referred to as lightweight processes because they have their own stack but have access to shared data.

Multiple threads running in a process share: address space, heap, static data, code snippets, file descriptors, global variables, child processes, pending alerts, signals, and signal handlers.

Each thread has its own: program counters, registers, stacks, and state.

What is a process? What are the different states of the process?

The process is basically a program that is currently being executed. The main function of the operating system is to manage and handle all these processes. When a program is loaded into memory and becomes a process, it can be divided into four parts – stack, heap, text, and data. There are two types of processes:

Operating system processes
User processes

Process

Status: The different states of the process that a process goes through are as follows:

New state: In this state, a process has just been created.
Run: In this state, the CPU begins processing the process’s instructions.
Waiting: In this state, the process cannot run because it is just waiting for an event to occur
Ready: In this state, the process has all the available resources needed to run, but it waits to be allocated to the processor because the current CPU does not process the instructions passed by the process.
Terminate: In this state, the process is completed, that is, the process is executed.

What does FCFS mean?

FCFS (First Come, First Served) is an operating system scheduling algorithm that executes processes in the same order in which they arrived. To put it simply, the process that comes first is executed first. It is non-preemptive in nature. If the burst time of the first process is the longest of all jobs, FCFS scheduling can cause hunger issues. The burst time here refers to the time (in milliseconds) it takes for a process to execute. It is also considered to be the simplest and simplest operating system scheduling algorithm compared to other algorithms. The implementation of FCFS is usually managed with the help of FIFO (first-in, first-out) queues.

What is reentrantion?

Reentrant is simply a feature where different clients can use and share a single copy of a program for a similar period of time. This concept is usually related to operating system code and does not involve concurrency. It has two main features:

The program code cannot be changed or modified by itself.
Local data for each client process needs to be stored on a different disk.

What is a scheduling algorithm? Name different types of scheduling algorithms.

A scheduling algorithm is a process that improves efficiency by utilizing the maximum CPU and providing the minimum wait time for the task. It simply deals with deciding which outstanding requests to allocate resources to. Its main purpose is to reduce resource scarcity and ensure equity among all parties using resources. In short, it is used to allocate resources among various competing tasks.

Types of Scheduling Algorithms The different types of scheduling algorithms are given below:

What is the difference between pagination and segmentation?

Paging: It is typically a memory management technique that allows the operating system to retrieve processes from secondary storage into main memory. It is a non-contiguous allocation technique that divides each process in the form of pages.
Segmentation: A memory management technique that divides a process into modules and parts of different sizes. These parts and modules are called segments that can be assigned to inheritance.

pagination	sublevel
It is invisible to programmers.	It is visible to programmers.
In this case, the size of the page is fixed.	In this case, the size of the segment is not fixed.
Programs and data cannot be separated in pagination.	Programs and data can be separated in segments.
It allows the cumulative total of the virtual address space to span the physical main memory.	It allows all programs, data, and code to be broken down into separate address spaces.
It is mainly used in CPU and MMU chips.	It is mostly available on Windows servers that may support backward compatibility, whereas Linux has limited support.
Memory access is faster as compared to segmentation.	It is slower as compared to pagination.
In this case, the OS needs to maintain an idle frame.	In this case, the operating system needs to maintain a list of holes in the main memory.
In pagination, the type of fragment is internal.	In segments, the type of fragment is external.
The size of the page is determined by the available memory.	The size of the page is determined by the user.

What Are The Common Operating System Interview Questions: What Are Bumps in the Operating System?

Typically, CPUs perform less efficiently, while swapping or paging work is more. It spends more time exchanging or paging activities than execution. By assessing the level of CPU utilization, the system can detect jitter. This happens when the process doesn’t have enough pages, causing the page error rate to increase. It inhibits a lot of application-level processing that causes your computer’s performance to slow down or crash.

What is the main goal of multi-channel programming?

It refers to the ability to execute or execute multiple programs on a single-processor machine. This technique was introduced to overcome the problem of underutilization of CPU and main memory. To put it simply, it is to coordinate the simultaneous execution of various programs on a single processor (CPU). The main goal of multi-channel programming is to keep at least some processes running all the time. It simply improves CPU utilization because it organizes many jobs where the CPU always has a task to perform.

What does asymmetric clustering mean?

An asymmetric cluster is typically a system in which one of all the nodes is in hot standby mode while all the remaining nodes run different applications. It simply uses the whole or the entire hardware resource, so it is considered a more reliable system as compared to other systems.

What is the difference between multitasking and multiprocessing operating systems?

Multitasking: This is a system that allows for more efficient use of computer hardware. The system handles multiple tasks at the same time by quickly switching between various tasks. These systems are also known as time-sharing systems.

Multiprocessing: It is a system that allows multiple or multiple processors in a computer to work on two or more different parts of the same program at the same time. It is used to get more done in less time.

Multitasking	multiprocessing
It uses a single processor to perform multiple tasks at once.	It uses multiple processors to perform multiple tasks at once.
Here, there is only one number of CPUs.	Here, there is more than one CPU.
It’s more economical.	It’s not very economical.
It is less efficient than multiprocessing.	It is more effective than multitasking.
It allows for quick switching between various tasks.	It allows for the smooth handling of multiple tasks at once.
It takes more time to perform the task as compared to multiprocessing.	It takes less time to process the job as compared to multitasking.

What does socket mean in operating system?

Analysis of operating system interview questions: The socket in the OS is generally called the endpoint of the IPC (Interprocess Communication). Here, the endpoint is referred to as a combination of an IP address and a port number. Sockets are used to make it easy for software developers to create network-enabled programs. It also allows communication or exchange of information between two different processes on the same or different machines. It is mainly used in client-server based systems.

There are basically four types of sockets for socket types

, as follows:

Flow sockets
Datagram sockets
Sequential packet sockets
Original socket

Explain the zombie process?

A zombie process, or defunct process for short, is basically a process that terminates or completes but the entire process control block is not purged from main memory because it still has an entry in the process table to report to its parent process. It doesn’t consume any resources and is dead, but it’s still there. It also shows that the resource is held by the process and is not free.

What does cascade termination mean?

Cascading termination is a type of process termination where if the parent process is exiting or terminating, then the child process will also be terminated. It does not allow a child process to continue processing when its parent process is terminated. It is usually started by the operating system.

What is hunger and aging in OS?

Hunger can occur when we use priority scheduling or shortest job priority scheduling, and this algorithm is mostly used in CPU schedulers

Hunger: This is often a problem, usually when a process is unable to get the resources it needs to execute for an extended period of time. In this case, the low-priority process is blocked, and only the high-priority process can complete because the low-priority process lacks resources.

Aging: This is a technique used to overcome a situation or problem of hunger. It simply raises the priority of processes that wait for resources for a long time in the system. It is considered the best technique to solve the problem of hunger because it adds an aging factor to the priority of individual processes for each request for resources. It also ensures that a low-level queue job or process completes its execution.

A collection of advanced operating system interview questions and answers

What does semaphore mean in operating system? Why use it?

Semaphore is a signaling mechanism. It only saves a positive integer value. It simply solves the problem or problem with the critical zone during synchronization by using two atomic operations i.e. wait() and signal().

There are generally two types of semaphores of the types of
semaphores, which are as follows:

Binary semaphore
Count semaphores

Binary semaphore	mutexes
It allows various process threads to acquire a limited instance of a resource until it becomes available.	It allows individual process threads to acquire only one share at a time.
Its functionality is based on a signaling mechanism.	Its functionality is based on a locking mechanism.
Binary semaphores are much faster as compared to Mutex.	The mutex is slower as compared to the binary semaphore.
It’s basically an integer.	It’s basically an object.

What is a Kernel and what are its main features?

A kernel is basically a computer program that is often thought of as the core component or module of an operating system. It is responsible for handling, managing, and controlling all operations of computer systems and hardware. Whenever the system boots, the kernel is loaded first and remains in the main memory. It also acts as an interface between the user’s application and the hardware.

Features of the kernel:

It is responsible for managing all the computer resources like CPU, memory, files, processes, etc.
It facilitates or initiates the interaction between hardware and software components.
It manages the RAM memory so that all the running processes and programs work effectively and efficiently.
It also controls and manages all the main tasks of the operating system, as well as managing the access and use of various peripherals connected to the computer.
It schedules the work done by the CPU in order to perform each user’s work as efficiently as possible.

What are the different types of kernels?

There are basically five types of kernels, which are as follows:

Monolithic core
Microkernel
Hybrid kernels
Nanocore
Explicit kernel

What is the difference between writing a microkernel and a monolithic kernel?

Microkernel: It is a minimal operating system that performs only the important functions of the operating system. It contains only the minimum number of features and functionality required to implement an operating system.
Examples: Monolithic Kernel like QNX, Mac OS X, K42, etc

.: It is an operating system architecture that supports all the basic functions of computer components such as resource management, memory, files, etc.
Examples: Solaris, DOS, OpenVMS, Linux, etc.

Microkernel	Monolithic core
In this software or program, kernel services and user services exist in different address spaces.	In this software or program, kernel services and user services usually exist in the same address space.
It is smaller in size compared to a monolithic core.	It is larger in size as compared to the microkernel.
It is easily scalable compared to a monolithic core.	It is difficult to scale compared to the microkernel.
If the service crashes, it does affect the working of the microkernel.	If one service crashes, the entire system crashes in a single core.
It uses message queues for inter-process communication.	It uses signals and sockets to enable inter-process communication.

What is SMP (Symmetric Multiprocessing)?

SMP is often referred to as computer architecture, in which the processing of programs is done by multiple processors that share a common operating system and memory. If you want to take advantage of multiprocessor hardware, SMP is very much needed. It simply enables any processor to handle any task, regardless of where the data or resources for that particular task are located in memory. These systems are more reliable than single-processor systems.

What is a time-sharing system?

It is a system that allows multiple users to access specific system resources in multiple locations. In short, it performs multiple tasks on a single processor or CPU. As the name suggests, it’s about sharing time across multiple slots for multiple processes. It also allows different users from different locations to use a particular computer system at the same time, so it is considered one of the important types of operating systems.

What is context switching?

Context switching is basically the process of saving the context of one process and loading the context of another process. It is a cost-effective and time-saving measure for CPU execution as it allows multiple processes to share a single CPU. As a result, it is considered an essential part of modern operating systems. The operating system uses this technique to switch a process from one state to another, that is, from a running state to a ready state. It also allows a single CPU to process and control a variety of different processes or threads without even requiring additional resources.

What are the common interview questions for operating systems: What is the difference between kernel and operating system?

Kernel: A kernel is a system program that controls all the programs running on your computer. The kernel is basically a bridge between the software and hardware of the system.

Operating system: An operating system is a system program that runs on a computer and provides an interface for computer users to operate on the computer conveniently.

core	operating system
It is considered to be the core component of the operating system	It is considered to be system software.
It is generally responsible for translating user commands into machine-level commands.	It is generally responsible for managing system resources.
It simply acts as an interface between the hardware and the application.	It simply acts as an interface between the hardware and the user.
It also performs functions such as process management, file management, device management, I/O communication, and more.	It also performs functions such as providing security for data and files in the system, providing access control to users, maintaining system privacy, and more.
Its types include microkernels, monolithic kernels, etc.	Its types include single-program and multi-program batch systems, distributed operating systems, and real-time operating systems.

What is the difference between a process and a thread?

Process: It is basically a program that is currently executed by one or more threads. It is a very important part of modern operating systems.

Thread: It is an execution path consisting of program counters, thread IDs, stacks, and sets of registers within the process.

process	thread
It is a computer program that is being executed.	The component or entity of a process is the smallest unit of execution.
These are heavyweight operators.	These are lightweight operators.
It has its own memory space.	It uses the memory of the process to which they belong.
Creating a process is more difficult than creating a thread.	It’s easier to create a thread than to create a process.
It requires more resources as compared to threads.	It requires fewer resources as compared to processes.
It takes more time to create and terminate a process as compared to threads.	It takes less time to create and terminate threads than a process.
It usually runs in a separate memory space.	It usually runs in a shared memory space.
It doesn’t share data.	It shares data with each other.
It can be divided into multiple threads.	It can’t be subdivided anymore.

What are the parts of the process?

The process basically has four parts, which are as follows:

Stack: Used for local variables and returns addresses.
Heap: Used for dynamic memory allocation.
Data: It stores both global and static variables.
Code or text: It includes compiled program code.

What is a deadlock in an operating system? What are the necessary conditions for a deadlock?

A deadlock is usually a case where a group of processes is blocked because each process holds a resource and waits to acquire a resource held by another process. In this case, two or more processes are simply trying to execute at the same time and waiting for each process to finish their execution because they depend on each other. Whenever a deadlock occurs in a program, we can see manual issues in the system. This is one of the common issues you can see in multiprocessing.

The necessary conditions for deadlocks There are basically the following four necessary conditions for

deadlocks:

mutually exclusive
Hold and wait
Not preemptive
Circular waits or resource waits

What does Belady anomaly mean?

Operating System Interview Question Analysis: In the operating system, process data is loaded in fixed-size blocks, and each block is called a page. The processor loads these pages into fixed-size blocks of memory called frames. Belady’s Anomaly is a phenomenon where if we increase the number of frames in memory, then the number of page faults also increases. This is usually the case when we use the FIFO (first-in, first-out) page replacement algorithm.

Collection of Operating Systems Interview Questions and Answers: What is Spooling in Operating System?

Spooling only represents an online synchronous peripheral operation. This is called putting data from various I/O jobs into a buffer. In this context, a buffer is a special area of memory or hard disk that can be accessed by I/O devices. It is used to mediate between computer applications and slow peripherals. It is very useful and important because devices access or fetch data at different rates. This operation also uses the disk as a very large buffer and is able to overlap the I/O operations of one task with the processor operations of another.