35 Operating Systems Interview Questions and Answers (2024)

Blog / 35 Operating Systems Interview Questions and Answers (2024)

An operating system is a software program that acts as an intermediary between a computer user and the computer hardware.

While this information might not be practical for many modern developers...

It is 100% worth understanding.

Not only will it give you a better understanding of what is happening in the core of the computer...

It will also allow you to show off in interviews as it shows a level of understanding that most candidates don't have these days.

Q1.

What is an operating system?

Junior

An operating system (OS) is a software program that acts as an intermediary between a computer user and the computer hardware.
It serves as the backbone of a computer system, providing essential services for computer programs and managing hardware resources.
The OS enables user interaction with the system through a user interface, organizes file storage, manages tasks and system resources, and facilitates networking and security.
Common examples include Microsoft Windows, macOS, Linux, and Unix.

Q2.

Explain the difference between a process and a thread.

Junior

A process and a thread are both fundamental units of execution in computing, but they differ in scope and resource allocation:
- Process: A process is an independent program in execution, which has its own memory space, including code, data, and system resources. Each process operates separately and is isolated from other processes.
- Thread: A thread is a subdivision of a process. It is the smallest unit of processing that can be scheduled by an operating system. Threads within the same process share the same memory space and resources, but each thread maintains its own program counter, register set, and stack.

Q3.

What is virtual memory?

Junior

Virtual memory is a memory management feature of an operating system that uses both hardware and software to simulate more memory space than the physical memory (RAM) available.
It extends RAM by temporarily transferring data to disk storage, allowing a computer to handle larger applications and multitask more effectively.

Preparing for a tech interview?👉Top 58 Operating Systems questions

Q4.

What is a mutex, and why is it important in concurrent programming?

Junior

A mutex (short for mutual exclusion) is a synchronization primitive used to protect shared resources in a multi-threaded environment.
It ensures that only one thread can access a critical section of code at a time, preventing data corruption and race conditions.

Q5.

Explain the concept of a semaphore.

Junior

A semaphore is a synchronization primitive that can be used to control access to a shared resource. It maintains a counter and allows a limited number of threads to access the resource simultaneously.
Semaphores are useful for managing access to resources with limited capacity.

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Q6.

What is a shell in the context of operating systems?

Junior

A shell is a command-line interface that allows users to interact with the operating system by entering commands.
It serves as an intermediary between the user and the operating system, making it easier to manage files, execute programs, and configure system settings.

Q7.

Explain the difference between preemptive and non-preemptive scheduling.

Junior

Preemptive scheduling allows the operating system to forcibly interrupt a running process and allocate CPU time to another process.
Non-preemptive scheduling allows a process to run until it voluntarily relinquishes the CPU, typically resulting in longer response times.

Q8.

What is a page fault?

Junior

A page fault occurs when a process attempts to access a page of memory that is not currently in physical RAM but is on disk.
The operating system handles page faults by fetching the required page from disk into RAM, updating page tables, and resuming the interrupted process.

Q9.

Explain the concept of a deadlock in the context of operating systems.

Junior

Deadlock is a situation where two or more processes are unable to proceed because they are each waiting for the other to release a resource.
Key characteristics of a deadlock include:
- Mutual Exclusion: Each resource involved is non-shareable and can only be held by one process at a time.
- Hold and Wait: Processes holding resources are waiting to acquire additional resources held by other processes.
- No Preemption: Resources cannot be forcibly taken away from a process; they must be released voluntarily.
- Circular Wait: There exists a circular chain of processes, each waiting for a resource held by the next member in the chain.
Deadlocks can be prevented through techniques like resource allocation graphs, timeouts, or avoiding circular waits.
They can also be resolved using techniques such as process termination or resource preemption.

Q10.

What is a kernel in an operating system

Mid

The kernel is the core component of an operating system that manages hardware resources and provides essential services to user processes.
It performs tasks like process scheduling, memory management, device management, and system call handling.

Q11.

Explain the role of an interrupt in the context of CPU operation.

Mid

An interrupt is a signal sent by a hardware device or software to the CPU to request immediate attention. It can be used for various purposes, including handling hardware events (e.g., keyboard input), error conditions, and system calls.
When an interrupt occurs, the CPU temporarily stops executing the current program and handles the interrupt before resuming normal operation.

Q12.

What is a system call, and why is it necessary for user processes to interact with the kernel?

Mid

A system call is a mechanism that allows user processes to request services or functionality provided by the operating system kernel.
It is necessary because it provides a controlled interface for user programs to interact with the lower-level kernel functions, such as file I/O, process creation, and network communication.

Q13.

Explain the role of the Process Control Block (PCB) in process management.

Mid

The PCB is a data structure maintained by the operating system for each process. It contains information about the process's state, program counter, CPU registers, memory allocation, and other relevant data.
The PCB is crucial for context switching between processes and managing their execution.

Q14.

What is a context switch, and why is it necessary in a multitasking operating system?

Mid

A context switch is the process of saving the state of a running process and loading the state of another process for execution.
It is necessary in multitasking operating systems to allow multiple processes to share the CPU efficiently.
Context switches occur when the operating system scheduler decides to switch from one process to another.

Q15.

Explain the role of the page table in virtual memory systems.

Mid

A page table is a data structure used by the operating system to map virtual memory addresses to physical memory addresses.
It enables the CPU to access data in virtual memory transparently, allowing processes to use more memory than physically available by using paging or segmentation.

Q16.

What is the main purpose of multiprogramming?

Mid

The main purpose of multiprogramming is to maximize the utilization of a computer's processing power by allowing multiple programs to run concurrently.
This is achieved by having the CPU switch rapidly between programs, reducing idle time caused by I/O operations or other waiting states.
As a result, multiprogramming increases system efficiency and throughput, ensuring that the CPU is always actively processing tasks.

Q17.

Explain the purpose of the I/O scheduler in operating systems.

Mid

The I/O scheduler determines the order in which I/O requests from processes are serviced by disk drives.
It optimizes disk I/O by minimizing seek times and maximizing throughput. Common scheduling algorithms include CFQ (Completely Fair Queuing) and deadline scheduling.

Q18.

Explain the concept of file permissions in Unix-like operating systems.

Mid

File permissions control access to files and directories in Unix-like systems.
The three types of permissions are read (r), write (w), and execute (x). They represent whether a user or group can read, modify, or execute a file or directory.

Q19.

Explain the role of the Process Identifier (PID) in process management.

Mid

A PID is a unique numerical identifier assigned to each process in an operating system. PIDs are used to track and manage processes, allowing the system to identify and reference them.
They are assigned sequentially as processes are created and are significant for process management, signal handling, and resource allocation.

Q20.

What is pooling?

Mid

Pooling in computing refers to the practice of maintaining a group of resources that are kept ready to use, rather than acquiring and releasing them on demand.
Commonly used in scenarios like database connections, thread management, or memory allocation, pooling helps in optimizing performance and resource utilization.

Q21.

Explain the concept of a zombie process in Unix-like operating systems.

Mid

A zombie process is a terminated child process that has not yet been reaped by its parent. It exists in the process table to allow the parent to retrieve its exit status.
Zombie processes are created when a parent does not call the wait() system call to collect the child's exit status.
They can be eliminated by having the parent call wait().

Q22.

Explain the concept of a zombie process in Unix-like operating systems.

Mid

A zombie process is a terminated child process that has not yet been reaped by its parent. It exists in the process table to allow the parent to retrieve its exit status.
Zombie processes are created when a parent does not call the wait() system call to collect the child's exit status.
They can be eliminated by having the parent call wait().

Q23.

What is a system V IPC (Inter-Process Communication) and how is it used for communication between processes in Unix-like systems?

Mid

System V IPC provides a set of mechanisms for inter-process communication, including message queues, shared memory, and semaphores.
These mechanisms allow processes to exchange data and coordinate activities efficiently.

Q24.

Explain RTOS.

Mid

An RTOS (Real-Time Operating System) is designed for applications requiring immediate processing and a predictable response time.
It prioritizes tasks, manages resources efficiently, and minimizes latency, ensuring timely processing of real-time data.
Commonly used in embedded systems and critical applications like medical devices and industrial machines, an RTOS is essential where reliability and timing precision are paramount.

Q25.

What is demand paging?

Mid

Demand paging is a memory management technique where pages are loaded into physical memory only when they are accessed (demanded) by running processes.
It improves memory utilization by reducing the need to load all pages into memory at once, making more efficient use of available physical memory.

Q26.

Explain the concept of a trap or exception in the context of operating systems.

Mid

A trap or exception is a mechanism that transfers control from a user-level program to the operating system kernel when an error or exceptional condition occurs, such as a divide-by-zero error or an illegal instruction.
Traps are used to handle and recover from errors, ensuring system stability.

Q27.

What is a critical section in concurrent programming?

Mid

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Q28.

Explain the concept of a race condition in concurrent programming.

Mid

Q29.

What is a daemon process in Unix-like operating systems?

Senior

Q30.

What is the purpose of an interrupt vector table in the context of operating systems?

Senior

Q31.

What is a memory-mapped file?

Senior

Q32.

Explain the concept of a memory leak in software development.

Senior

Q33.

What is RAID?

Senior

Q34.

Name some RAID levels?

Senior

Q35.

Explain the concept of thrashing in virtual memory systems.

Senior