Operating Systems: Processes, Memory, and Files

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Questions and Answers

Consider an OS employing a multi-level feedback queue scheduling algorithm. Which scenario would most likely trigger a process being demoted to a lower priority queue?

  • The process has exceeded its allocated time quantum multiple times, suggesting CPU-bound behavior. (correct)
  • The process has experienced several page faults, indicating memory contention.
  • The process has voluntarily relinquished the CPU while awaiting I/O completion.
  • The process has been preempted by a higher-priority process to ensure responsiveness.

An operating system uses the Banker's Algorithm for deadlock avoidance. Given a system with 5 processes and 3 resource types (A, B, C), what is the primary data structure used by the Banker's Algorithm to determine if a resource allocation request can be safely granted?

  • A resource allocation graph depicting the current resource assignments.
  • Matrices representing the maximum resource needs of each process, the current allocation, and the available resources. (correct)
  • A priority queue of processes ordered by their resource requirements.
  • A wait-for graph showing processes waiting for resources held by other processes.

In the context of virtual memory, what is the most significant challenge addressed by a 'page replacement algorithm' and which of the following scenarios highlights this challenge?

  • Preventing unauthorized memory access by implementing memory protection mechanisms.
  • Minimizing external fragmentation by re-arranging the order of pages in physical memory.
  • Optimizing disk access times by clustering frequently accessed pages together.
  • Reducing the page fault rate when the number of available physical pages is less than the program's working set size. (correct)

Consider an OS that combines segmentation and paging for memory management. How does the Translation Lookaside Buffer (TLB) typically function within this architecture?

<p>The TLB caches translations from the segment number and page number to the physical memory address. (D)</p> Signup and view all the answers

An operating system implements a file system with journaling. Which of the following scenarios illustrates the MOST significant benefit of journaling?

<p>Improved data consistency and recovery speed after a system crash or power failure. (B)</p> Signup and view all the answers

In the context of inter-process communication (IPC), contrast message queues with shared memory. Which statement BEST describes a key trade-off between them?

<p>Shared memory provides faster communication but requires explicit synchronization mechanisms to avoid race conditions. (D)</p> Signup and view all the answers

An OS uses a preemptive priority scheduling algorithm. A high-priority process enters a critical section and disables interrupts. What potential problem might arise, and how could the OS mitigate this?

<p>Priority inversion; mitigate using priority inheritance or priority ceiling protocols. (C)</p> Signup and view all the answers

Consider a distributed operating system using a distributed shared memory (DSM) model. What is a major consistency challenge unique to DSM compared to shared memory in a single-machine OS?

<p>Maintaining cache coherence across multiple nodes in the distributed system. (D)</p> Signup and view all the answers

Which of the following scenarios would be LEAST effectively addressed by using a real-time operating system (RTOS) as opposed to a general-purpose OS?

<p>Running a web server that handles a high volume of concurrent user requests. (D)</p> Signup and view all the answers

An operating system is designed with a microkernel architecture. What is a potential drawback of this architecture compared to a monolithic kernel, and how might it manifest in practice?

<p>Reduced performance due to increased overhead from inter-process communication between system services. (B)</p> Signup and view all the answers

How does the concept of 'copy-on-write' (COW) optimize resource utilization, and in which of the following scenarios is it most effectively applied?

<p>By sharing physical memory pages between processes until one process modifies the data. (C)</p> Signup and view all the answers

In the context of distributed file systems, what is a key challenge in maintaining consistency, and how do techniques like 'leases' address this challenge?

<p>Managing concurrent writes to the same file; leases grant exclusive or shared access rights for a limited time. (B)</p> Signup and view all the answers

What is the 'Byzantine Generals Problem' in the context of distributed systems, and what is its primary implication for operating system design?

<p>A consensus problem where some components may provide faulty information, making it difficult to reach a reliable agreement. (D)</p> Signup and view all the answers

Consider an OS using capability-based security. What is a key advantage of capability-based security compared to access control lists (ACLs), and in what scenario is this advantage most apparent?

<p>Simplified revocation of access rights as capabilities are held by the object, not the subject. (D)</p> Signup and view all the answers

An operating system supports dynamic linking. What is a potential security risk associated with dynamic linking, and how can 'address space layout randomization' (ASLR) mitigate this risk?

<p>Vulnerability to code injection attacks if shared libraries are not properly signed and verified. (B)</p> Signup and view all the answers

Flashcards

Operating System (OS)

Software that manages computer hardware and software resources, providing common services for computer programs and acting as an intermediary between applications and the computer hardware.

Process

A program in execution, managed by the OS for creation, scheduling, and termination.

Memory Management

The OS handles allocation and deallocation of memory space to programs as needed.

Virtual Memory

Using disk space to extend RAM, allowing execution of programs larger than physical memory.

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Paging

Dividing memory into fixed-size blocks, allowing the OS to load only needed portions of programs.

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File System

Organizes and stores data on storage devices in a hierarchical structure.

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Device Management

Manages device communication through specialized software.

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Process Scheduling

Determines which processes run when and for how long to maximize CPU utilization.

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First-Come, First-Served (FCFS)

Processes run in the order they arrive.

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Round Robin

Each process gets a small time slice in rotation.

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Priority Scheduling

Higher priority processes run first.

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Concurrency

Managing multiple processes executing simultaneously.

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Deadlock

A situation where two or more processes are unable to proceed because each is waiting for resources held by the others.

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Graphical User Interface (GUI)

Visual interface with windows, icons, and menus.

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Kernel

The core part of the operating system.

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Study Notes

  • An operating system (OS) is software managing computer hardware and software resources.
  • The OS provides services for computer programs and mediates between applications and hardware.

Process Management

  • A process is a program in execution, managed by the OS for creation, scheduling, and termination.
  • Example: Opening Microsoft Word initiates an OS process with allocated memory and CPU time.

Memory Management

  • The OS handles allocation/deallocation of memory space to programs.
  • Virtual memory extends RAM using disk space.
  • Example: Running multiple applications may cause the OS to move data to the hard disk to free up RAM.
  • Paging divides memory into fixed-size blocks.
  • Example: A 16MB program might be divided into 4KB pages, and the OS loads only needed pages into physical memory.

File Systems

  • File systems organize and store data in a hierarchical structure.
  • Example: Windows uses NTFS or FAT32, while Linux often uses ext4 to organize files in folders.

Device Management

  • The OS manages device communication through drivers.
  • Example: Plugging in a printer prompts the OS to load its driver for application access.

Process Scheduling

  • Process scheduling determines when and how long processes run, maximizing CPU use.
  • First-Come, First-Served (FCFS) runs processes in order of arrival.
  • Round Robin gives each process a small time slice in rotation.
  • Priority Scheduling runs higher priority processes first.
  • Example: Background virus scans get lower priority while typing, but video rendering gets higher priority.

Concurrency and Deadlocks

  • Concurrency is managing multiple processes at the same time.
  • Example: Playing music, browsing, and downloading files simultaneously.
  • Deadlock is when processes can't proceed because each waits for resources held by others.
  • Example: Process A holds Resource 1 and waits for Resource 2, while Process B holds Resource 2 and waits for Resource 1.

User Interface

  • Command-Line Interface (CLI) is text-based, where users type commands.
  • Example: Windows Command Prompt or Linux Terminal.
  • Graphical User Interface (GUI) is visual, using windows, icons, and menus.
  • Example: Windows Desktop, macOS, or Ubuntu Desktop.

Protection and Security

  • Mechanisms control access to system resources.
  • Example: User accounts, permissions, and authentication determine file access and actions.

Key Operating System Questions

  • Database management is not a function of an OS.
  • Thrashing is excessive page swapping.
  • Priority Scheduling can lead to starvation.
  • A semaphore is a synchronization tool.
  • The kernel is the core part of an operating system.
  • Virtual memory allows running programs larger than physical memory.
  • A deadlock condition is when a process waits indefinitely.
  • fork() creates a new process in UNIX/Linux.
  • A daemon in UNIX/Linux is a background process.
  • VxWorks is an example of a real-time operating system.

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