20 Common OS interview questions (Operating System) along with possible answers
What is an Operating System?
Answer: An Operating System is software that acts as an intermediary between computer hardware and user applications. It provides services such as process management, memory management, file system management, and device management.
Explain the difference between a process and a thread.
Answer: A process is an independent program with its own memory space, while a thread is a lightweight process within a process. Threads share the same memory space, allowing for more efficient communication.
What is the purpose of the kernel in an operating system?
Answer: The kernel is the core component of an operating system. It manages system resources, handles hardware communication, and provides essential services for other parts of the operating system and user applications.
Describe the difference between multiprogramming and multitasking.
Answer: Multiprogramming involves running multiple programs simultaneously, while multitasking involves switching between multiple tasks within a single program.
What is virtual memory?
Answer: Virtual memory is a memory management technique that uses both RAM and disk space to simulate larger RAM. It allows running processes to use more memory than physically available by swapping data between RAM and the hard disk.
Explain the difference between a file and a directory.
Answer: A file is a collection of data or information stored under a specific name, while a directory is a container for files and other directories.
What is a deadlock, and how can it be avoided?
Answer: A deadlock is a situation where two or more processes are unable to proceed because each is waiting for the other to release a resource. Deadlocks can be avoided through proper resource allocation, using timeouts, or implementing deadlock detection and recovery mechanisms.
What is the role of the page table in virtual memory management?
Answer: The page table is used to map virtual addresses to physical addresses in virtual memory systems. It helps the operating system keep track of the location of each page in the physical memory.
Explain the concept of a semaphore.
Answer: A semaphore is a synchronization tool used in concurrent programming to control access to shared resources. It is a variable that can be incremented or decremented, and processes must request access by checking the semaphore’s value.
What is the purpose of an interrupt?
Answer: Interrupts are signals generated by hardware or software to interrupt the normal execution of a program. They allow the operating system to respond to events such as hardware errors, user inputs, or the completion of I/O operations.
What is the difference between fragmentation and compaction?
Answer: Fragmentation is the division of memory into small, non-contiguous blocks, leading to inefficient use of memory. Compaction is the process of rearranging memory to consolidate fragmented blocks, improving overall memory utilization.
Explain the concept of a file system.
Answer: A file system is a method used by the operating system to organize and store files on a storage medium. It manages file naming, storage, retrieval, and access control.
How does a context switch work?
Answer: A context switch is the process of saving the state of a running process and loading the saved state of another process. It allows the operating system to switch between multiple processes, giving the appearance of concurrent execution.
What is the difference between process scheduling and CPU scheduling?
Answer: Process scheduling involves the selection of processes to be executed, while CPU scheduling involves determining which process will use the CPU at a given time. Process scheduling is a broader concept that includes CPU scheduling.
What is a shell in the context of an operating system?
Answer: A shell is a command-line interface that allows users to interact with the operating system. It interprets user commands and communicates with the kernel to execute those commands.
Explain the purpose of a device driver.
Answer: A device driver is a software component that facilitates communication between the operating system and hardware devices. It allows the operating system to control and utilize various hardware peripherals.
What is the difference between a process and a program?
Answer: A program is a set of instructions stored in a file, while a process is an instance of a program that is currently executing. A program becomes a process when it is loaded into memory.
Describe the role of the system call in an operating system.
Answer: System calls are interfaces provided by the operating system to allow user-level programs to request services from the kernel. They provide a secure and controlled way for applications to interact with the underlying hardware.
What is the difference between preemptive and non-preemptive scheduling?
Answer: Preemptive scheduling allows the operating system to forcibly interrupt a currently running process to start or resume another, while non-preemptive scheduling allows a process to run until it voluntarily releases the CPU.
How does the operating system manage file permissions?
Answer: The operating system assigns permissions to files and directories using a set of rules that define which users or groups can read, write, or execute a file. Permissions are set based on ownership and access control lists.
