OS Interview Questions and Answers for 2 years experience

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100 OS Interview Questions & Answers

  1. What is an operating system?

    • Answer: An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs. It acts as an intermediary between users and hardware, allowing users to interact with the computer without needing to understand the low-level details of hardware operation.

  2. Explain the different types of operating systems.

    • Answer: Operating systems can be categorized in several ways: By their interface (command-line, graphical), by the number of users they support (single-user, multi-user), by the number of tasks they can handle concurrently (single-tasking, multitasking), by their architecture (embedded, real-time, distributed), and by their kernel type (monolithic, microkernel).

  3. What is a process?

    • Answer: A process is an instance of a computer program that is being executed. It includes the program's code, its data, and its execution context (e.g., program counter, registers).

  4. What is a thread?

    • Answer: A thread is a lightweight unit of execution within a process. Multiple threads can exist within a single process, sharing the same memory space and resources. This allows for concurrency within a single program.

  5. Explain the difference between a process and a thread.

    • Answer: Processes are independent entities with their own memory space, while threads share the same memory space within a process. Processes are heavier to create and manage than threads. Inter-process communication (IPC) is more complex than inter-thread communication.

  6. What is context switching?

    • Answer: Context switching is the process of saving the state of a currently running process or thread and loading the state of another process or thread, allowing the operating system to switch between different processes or threads efficiently.

  7. What is a kernel?

    • Answer: The kernel is the core of the operating system. It manages the system's resources, such as memory, CPU, and I/O devices. It's responsible for scheduling processes, handling interrupts, and providing services to other parts of the OS and applications.

  8. Explain different types of scheduling algorithms.

    • Answer: Common scheduling algorithms include First-Come, First-Served (FCFS), Shortest Job First (SJF), Priority Scheduling, Round Robin, and Multilevel Queue Scheduling. Each has its advantages and disadvantages in terms of fairness, efficiency, and response time.

  9. What is deadlock?

    • Answer: Deadlock occurs when two or more processes are blocked indefinitely, waiting for each other to release resources that they need. This creates a standstill where no process can proceed.

  10. How can deadlock be prevented or avoided?

    • Answer: Deadlock can be prevented or avoided using techniques like mutual exclusion, hold and wait, no preemption, and circular wait prevention. These methods involve carefully managing resource allocation and process execution.

  11. What is a page fault?

    • Answer: A page fault occurs when a process tries to access a page of memory that is not currently loaded into RAM. The OS then needs to load the page from secondary storage (like a hard drive) into RAM.

  12. Explain virtual memory.

    • Answer: Virtual memory is a memory management technique that provides processes with the illusion of having more memory than is physically available. It uses a combination of RAM and secondary storage to create a larger address space.

  13. What is paging?

    • Answer: Paging is a memory management scheme that divides both physical and virtual memory into fixed-size blocks called pages and frames, respectively. This allows for efficient allocation and management of memory.

  14. What is segmentation?

    • Answer: Segmentation is another memory management scheme that divides memory into variable-sized segments, each corresponding to a logical division of a program (e.g., code, data, stack). This allows for more flexible memory allocation.

  15. What are system calls?

    • Answer: System calls are requests made by a program to the operating system's kernel for services such as file I/O, memory allocation, process creation, etc.

  16. What is an interrupt?

    • Answer: An interrupt is a signal that temporarily suspends the execution of a currently running process or thread to handle a more urgent event, such as a hardware signal or a software exception.

  17. Explain the difference between a hard link and a symbolic link.

    • Answer: A hard link is a pointer to an inode (file data structure), while a symbolic link is a pointer to a filename. Deleting a hard link does not delete the file unless it's the last one, while deleting a symbolic link does not affect the original file.

  18. What is a file system?

    • Answer: A file system is a method for organizing and managing files on a storage device (like a hard drive). It provides a way to store, retrieve, and manipulate files.

  19. What are different types of file systems?

    • Answer: Examples include FAT32, NTFS, ext4, and btrfs. Each has different characteristics in terms of features, performance, and compatibility.

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