Operating System Changes and Structure
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Questions and Answers

What is a key characteristic of flash memory?

  • Primarily used for caching
  • Nonvolatile and retains contents without power (correct)
  • Faster than DRAM
  • Requires power to retain contents

    • Which memory type can be as fast as DRAM while being nonvolatile?

  • EEPROM
  • Flash memory
  • SRAM
  • NVRAM (correct)

    • What role does the device controller play in a computer system?

  • Stores all the system's data permanently
  • Manages local buffer storage and registers for specific devices (correct)
  • Functions as the primary storage for the operating system
  • Directly interacts with the CPU

    • What is the purpose of a device driver in an operating system?

    <p>To provide a uniform interface for the device controller to the operating system</p> Signup and view all the answers

    What does the operating system do when starting an I/O operation?

    <p>Loads registers within the device controller</p> Signup and view all the answers

    Which of the following is NOT a characteristic of caches in a memory system?

    <p>Increases power consumption</p> Signup and view all the answers

    How many devices can potentially be attached to a SCSI controller?

    <p>Seven or more</p> Signup and view all the answers

    What is a common drawback of flash memory compared to DRAM?

    <p>Flash memory is slower than DRAM</p> Signup and view all the answers

    What is the purpose of the mode bit in a computer's hardware?

    <p>To indicate the current execution mode.</p> Signup and view all the answers

    Which of the following statements is true regarding user mode and kernel mode?

    <p>Kernel mode allows unrestricted access to system resources.</p> Signup and view all the answers

    What occurs when a user process makes a system call?

    <p>The process transitions from user mode to kernel mode.</p> Signup and view all the answers

    What is another name for kernel mode?

    <p>Privileged mode</p> Signup and view all the answers

    In the context of dual-mode operation, what does the transition from user mode to kernel mode allow?

    <p>Interaction with system services and resources.</p> Signup and view all the answers

    What is the main advantage of using direct memory access (DMA) over interrupt-driven I/O?

    <p>DMA allows the CPU to execute other tasks while data is being transferred.</p> Signup and view all the answers

    How does the device driver communicate completion of an I/O operation when using DMA?

    <p>It generates a single interrupt per block of data transferred.</p> Signup and view all the answers

    What is a likely drawback of using interrupt-driven I/O for bulk data transfers?

    <p>It causes increased overhead due to multiple interrupts.</p> Signup and view all the answers

    In which architecture does DMA become even more effective by allowing concurrent communication?

    <p>Switch architecture</p> Signup and view all the answers

    What role does the device controller play in the DMA process?

    <p>It performs data transfers directly to and from memory.</p> Signup and view all the answers

    What is a primary benefit of multiprogramming in operating systems?

    <p>Ensures that the CPU never sits idle</p> Signup and view all the answers

    Where are jobs typically kept before being allocated to main memory in a multiprogramming system?

    <p>In the job pool on disk</p> Signup and view all the answers

    What happens when a job in a multiprogrammed system needs to perform an I/O operation?

    <p>The operating system switches to execute another job</p> Signup and view all the answers

    Which of the following best describes the role of the operating system in a multiprogramming environment?

    <p>To manage job scheduling and resource allocation</p> Signup and view all the answers

    What is the main limitation of a non-multiprogrammed system compared to a multiprogrammed one?

    <p>It cannot run programs concurrently.</p> Signup and view all the answers

    What determines the set of jobs currently in memory in a multiprogramming system?

    <p>The size of main memory available</p> Signup and view all the answers

    Which component of a multiprogramming system facilitates job switching when a job cannot proceed?

    <p>Operating system job scheduler</p> Signup and view all the answers

    Which of the following statements is NOT a characteristic of multiprogramming systems?

    <p>They execute programs in a strictly sequential manner.</p> Signup and view all the answers

    What is the main purpose of multiprogrammed systems?

    <p>To utilize system resources effectively</p> Signup and view all the answers

    What distinguishes time-sharing systems from multiprogramming?

    <p>Time-sharing systems enable users to interact with programs directly.</p> Signup and view all the answers

    How does a time-shared operating system give the impression of exclusivity to users?

    <p>By rapidly switching among users so each feels isolated</p> Signup and view all the answers

    What happens to a process when it needs to perform I/O?

    <p>It typically pauses execution until the I/O is finished.</p> Signup and view all the answers

    What is a defining characteristic of a process in a time-shared operating system?

    <p>It typically runs for a short time before it completes or needs I/O.</p> Signup and view all the answers

    What is the expected response time for a user in a time-sharing system?

    <p>Less than one second</p> Signup and view all the answers

    Which of the following best describes the function of CPU scheduling in time-shared systems?

    <p>To manage rapid switches between user processes</p> Signup and view all the answers

    Why is it said that idle lawyers tend to become politicians in the content?

    <p>Because it reflects a humorous social commentary.</p> Signup and view all the answers

    Study Notes

    Operating System Changes and Structure

    • Substantial organizational changes were made, including integrating real-time systems throughout the text and reorganizing chapters on storage management and process synchronization.
    • Chapter 1 (Introduction) now includes updated coverage of multiprocessor and multicore systems, kernel data structures, mobile systems, cloud computing, and an overview of real-time systems.
    • Chapter 2 (Operating-System Structures) features new coverage of user interfaces for mobile devices (iOS and Android), and expanded coverage of Mac OS X.
    • Chapter 3 (Processes) covers multitasking in mobile operating systems, the multiprocess model in Google Chrome, and zombie and orphan processes in UNIX.
    • Chapter 4 (Threads) provides expanded coverage of parallelism and Amdahl's law, and a new section on implicit threading (OpenMP and Grand Central Dispatch).
    • Chapter 5 (Process Synchronization) now includes mutex locks, synchronization using OpenMP, and functional languages.
    • Chapter 6 (CPU Scheduling) features the Linux CFS scheduler, Windows user-mode scheduling, and integrated real-time scheduling algorithms.
    • Chapter 7 (Deadlocks) has no major changes.
    • Chapter 8 (Main Memory) covers swapping on mobile systems, Intel 32- and 64-bit architectures, and ARM architecture.
    • Chapter 9 (Virtual Memory) updates kernel memory management to include Linux SLUB and SLOB memory allocators.
    • Chapter 10 (Mass-Storage Structure) includes coverage of solid-state disks (SSD), flash memory (used in cameras, PDAs, and increasingly in general-purpose computers), and NVRAM (DRAM with battery backup).

    I/O Structure

    • Operating systems manage I/O extensively due to its importance for reliability and performance and the diverse nature of devices.
    • Computer systems have CPUs and multiple device controllers linked via a common bus. Each controller handles a specific device type (e.g., a SCSI controller can manage several devices).
    • Device controllers hold local buffers and special registers to move data between devices and the buffer.
    • Operating systems use device drivers for each controller, providing a unified interface.
    • An I/O operation begins with the device driver loading controller registers.
    • The controller reads the registers and initiates the data transfer to/from the device.
    • Controller interrupts the device driver when data transfer completes.
    • Device drivers return control to the OS, often returning data or status information.

    Interrupt-Driven I/O vs. DMA

    • Interrupt-driven I/O is effective for small data transfers but inefficient for bulk data movement (like disk I/O).
    • Direct Memory Access (DMA) moves blocks of data directly between device controller and memory without CPU intervention.
    • DMA generates only one interrupt per data block instead of numerous interrupts per byte, thus reducing overhead.
    • DMA allows the CPU to perform other tasks concurrently with data transfer.

    Computer System Architecture

    • Computer system consists of CPUs and multiple device controllers through a common bus.
    • High-end systems increasingly use switch rather than bus architecture, allowing concurrent communication among components.

    Operating-System Structure

    • Operating systems provide an environment for program execution.
    • Multiprogramming increases CPU utilization by constantly having a job ready to execute.
    • Jobs are initially on a disk (job pool).
    • The OS selects a job from memory to execute, switching to another job when the first job waits for I/O.
    • CPU is never idle as long as at least one job is ready.

    Time-Sharing Systems

    • Time-sharing (multitasking) extends multiprogramming by rapidly switching among jobs providing interactive user access.
    • Time-sharing requires an interactive system with rapid user response (typically <1 second).
    • Time-sharing OS allows multiple users to share the computer simultaneously.
    • Each user gets the illusion of exclusive computer use.
    • A process is a program executing in memory.
    • Processes often execute briefly before waiting for I/O (e.g., keyboard input, display output).

    Dual-Mode Operation

    • Hardware support distinguishes between operating system code and user code through different execution modes (e.g., user mode and kernel mode).
    • A mode bit in the hardware distinguishes between kernel and user modes.
    • This allows protection of operating system code and data.

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    Abraham Silberschatz-Operating System Concepts (9th,2012_12).pdf

    Description

    Explore the substantial updates in operating system concepts, focusing on real-time systems, multiprocessor architectures, and updated user interfaces. This quiz covers essential chapters detailing storage management, process synchronization, and advanced processes in various operating systems including mobile. Test your understanding of the latest advancements and structural changes in operating systems.

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