Operating System Interview Questions and Answers - Part I

Summary

This video script offers an in-depth exploration of operating systems, detailing their core functions like process, memory, and I/O management. It distinguishes between monolithic and microkernels, elucidating their advantages and disadvantages. The script also delves into process management, including concepts like context switching, mutex, and synchronization mechanisms. It explains inter-process communication methods, the role of daemons, and the intricacies of memory management, including virtual memory and the importance of page frames. Additionally, it covers deadlock conditions and the types of memory used in computing systems.

Takeaways

• 💻 An operating system (OS) is a collection of software that manages hardware resources and is the first program loaded on a computer.
• 🔧 Main functions of an OS include process management, memory management, I/O management, and filesystem management.
• 🏗️ The kernel is the core of an OS that manages resource sharing and device handling, acting as an intermediary between hardware and software.
• 🌐 Kernels can be monolithic, where all services are in one module, or microkernels, which are modular and easier to maintain.
• 🚫 Disadvantages of microkernels include larger memory footprint, performance loss, and complex process management.
• 🗣️ A command interpreter facilitates user interaction with the OS by interpreting commands from the keyboard or batch files.
• 🏃 Process management involves creating, deleting, scheduling, and synchronizing processes, which are programs in execution.
• ⚡ An interrupt is a signal from a device that prompts the CPU to handle it, with each interrupt having a service routine address.
• 🔮 A daemon is a background process that runs without user interaction, typically starting at boot time and ending at shutdown.
• 🧩 A zombie process is a terminated process that remains in the process table because its parent process has not yet removed it.
• 🔄 Pipes are an IPC mechanism for one-way communication between related processes, while named pipes (FIFOs) allow communication between unrelated processes.

Q & A

What is an operating system and what are some popular examples?

An operating system is a collection of software programs that control the allocation and usage of various hardware resources in a system. It is the first program to be loaded in the computer and runs in memory until the system is shut down. Some popular operating systems include DOS, Windows, and Solaris.

What are the primary functions of an operating system?

The main functions of an operating system are process management, memory management, input/output management, storage or filesystem management.

What is the role of a kernel in an operating system?

The kernel is the part of the operating system that handles all details of resource sharing and device handling. It can be considered the core of the OS, managing the core features and facilitating communication between software and hardware through system calls.

What are the main functions of a kernel?

The main functions of a kernel include process management, device management, memory management, interrupt handling, input/output communication, and filesystem management.

Explain the difference between monolithic and microkernels.

Monolithic kernels package all system services into a single module, leading to poor maintainability and a large kernel size. Microkernels follow a modular approach, making maintainability easier as only the concerned module needs to be altered and loaded for each function, and they help control the kernel's size.

What are the disadvantages of microkernels?

The main disadvantages of microkernels include a larger running memory footprint, performance loss due to the need for more software for interfacing, difficulty in fixing messaging works, and complicated process management.

What is a command interpreter and what is its purpose?

A command interpreter is a program that interprets command input through a keyboard or command batch file. It helps users interact with the OS and execute system programs or user applications.

What is a process and what are the basic functions of process management?

A process is a program that is running and under execution. On batch systems, it is called a job, while on time-sharing systems, it is called a task. Important functions of process management include creation and deletion of system processes, CPU scheduling, process communication, and synchronization.

What is an interrupt and how is it handled?

An interrupt is a signal from a device that prompts the control switch to handle the interrupts. Interrupt service routines are required, and the address of each routine is provided in a list maintained in the interrupt vector.

What is a daemon and how can you identify them in UNIX?

A daemon is a process that runs in the background without user interaction, usually starting at boot time and terminating when the system is shut down. In UNIX, daemon names usually end with 'd', such as httpd.

What is a zombie process and how does it occur?

A zombie process is a dead process that is not yet removed from the process table. It occurs when the parent process has terminated while the child process is still running, causing the child to remain as a zombie.

What is a pipe and when is it used?

A pipe is an Inter-Process Communication (IPC) mechanism used for one-way communication between two related processes. It is used when two processes wish to communicate in one direction.

What is a named pipe and how does it differ from a traditional pipe?

A named pipe, also known as a FIFO (First In, First Out), allows communication between unrelated processes. It is a pipe with an access point in the form of a file on the filesystem, allowing processes to read from or write to the pipe through the file.

What are the various IPC mechanisms?

Various IPC mechanisms include sockets, pipes, shared memory, signals, and message queues.

What is a semaphore and what are the possible operations on it?

A semaphore is a hardware or software variable that indicates the status of a common resource. Its purpose is to lock the resource being used by a process. The two possible operations on a semaphore are 'wait' and 'signal'.

What is context switching and why is it important?

Context switching is the process of saving the context of the currently running process and restoring the context of the next ready-to-run process. It is important for multitasking operating systems to manage the execution of multiple processes efficiently.

What is a mutex and how is it used?

A mutex, or mutual exclusion lock, is used to protect access to shared data resources. Threads can create and initialize a mutex to be used later. Before entering a critical region, the mutex is locked, and it is unlocked after exiting the critical region.

What is a critical section and why is it important?

A critical section is a section of code that can be executed only by one process at a time. It is important to prevent data corruption and ensure proper synchronization in multitasking environments.

What is synchronization and what are some different synchronization mechanisms?

Synchronization is the control of access to a resource that is available to two or more threads or processes. Different synchronization mechanisms include mutexes, semaphores, monitors, condition variables, critical regions, and read/write locks.

What is the basic difference between pre-emptive and non-preemptive scheduling?

Pre-emptive scheduling allows interruption of a process while it is executing and taking the CPU to another process. Non-preemptive scheduling ensures that a process keeps the CPU under control until it has completed execution.

What are the necessary conditions for a deadlock to occur?

The necessary conditions for a deadlock to occur include: at least one resource being occupied in a non-shareable condition, a process holding at least one resource waiting for more resources currently in use by other processes, and the existence of a circular wait.

What are the functions constituting the operating system's memory management?

The functions constituting the operating system's memory management include memory allocation and de-allocation, integrity maintenance, and swapping for virtual memory.

What are the different types of memories in an operating system?

The different types of memories in an operating system are main memory (also called primary memory or RAM), secondary memory (or backing storage), and cache for internal process memory.

What is compaction and why is it necessary?

Compaction is the process of moving scattered pieces of free memory close to each other to form a larger chunk of memory, allowing the system to run larger processes. It is necessary to optimize memory usage and prevent memory fragmentation.

What are page frames and pages in the context of virtual memory?

Page frames are fixed-size contiguous areas into which the main memory is divided by the virtual memory. Pages are same-sized pieces of logical memory of a program, typically ranging from 4 KB to 8 KB, depending on the addressing hardware of the machine. They improve system performance and reduce the requirement of physical storage.

What is the difference between logical and physical addresses?

Physical addresses are actual addresses used for fetching and storing data in main memory when a process is under execution. Logical addresses are generated by user programs and are converted by the loader into physical addresses during process loading.