21CSC202J Operating Systems Unit I
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Questions and Answers

What is an operating system?

A program that acts as an intermediary between a user of a computer and the computer hardware.

What are the components of a computer system? (Select all that apply)

  • Operating system (correct)
  • Application programs (correct)
  • Networking
  • Hardware (correct)

    • Which of the following are goals of an operating system? (Select all that apply)

  • Execute user programs (correct)
  • Make the computer system convenient to use (correct)
  • Increase hardware cost
  • Make solving user problems easier (correct)

    • What is the basic unit of computer storage?

    <p>Bit</p> Signup and view all the answers

    What does 'multiprogramming' mean?

    <p>Multiprogramming is the method of organizing jobs so that the CPU always has one to execute.</p> Signup and view all the answers

    A kilobyte is equal to 1,024 bytes.

    <p>True</p> Signup and view all the answers

    The CPU and I/O devices can execute __________.

    <p>concurrently</p> Signup and view all the answers

    Which of the following is NOT a type of storage discussed?

    <p>Cloud storage</p> Signup and view all the answers

    What is direct memory access (DMA)?

    <p>A method that allows I/O devices to transfer data directly to main memory without CPU interference.</p> Signup and view all the answers

    What is the role of interrupts in operating systems?

    <p>They provide control transfer to a service routine.</p> Signup and view all the answers

    What resources does a process need to accomplish its task?

    <p>CPU, memory, I/O, files, and initialization data.</p> Signup and view all the answers

    A single-threaded process has one program counter.

    <p>True</p> Signup and view all the answers

    What are the activities of process management in an operating system? (Select all that apply)

    <p>Providing mechanisms for process synchronization</p> Signup and view all the answers

    What does memory management determine?

    <p>What is in memory and when.</p> Signup and view all the answers

    File-system management is part of storage management.

    <p>True</p> Signup and view all the answers

    What is tertiary storage?

    <p>Optical storage and magnetic tape.</p> Signup and view all the answers

    What are the responsibilities of the I/O subsystem? (Select all that apply)

    <p>General device-driver interface</p> Signup and view all the answers

    ______ refers to the control of access of processes or users to resources defined by the OS.

    <p>Protection</p> Signup and view all the answers

    Which of the following is a user goal for an operating system? (Select all that apply)

    <p>Reliable</p> Signup and view all the answers

    What is the purpose of a system program?

    <p>To provide a convenient environment for program development and execution.</p> Signup and view all the answers

    What are common methods of operating system structure? (Select all that apply)

    <p>Simple structure</p> Signup and view all the answers

    What is modularity in operating systems?

    <p>Modularity refers to selecting layers such that each uses functions and services of only lower-level layers.</p> Signup and view all the answers

    Which operating system is partly based on the Mach microkernel?

    <p>Mac OS X</p> Signup and view all the answers

    What is a benefit of using a microkernel?

    <p>Easier to extend</p> Signup and view all the answers

    Microkernel communication takes place through shared memory.

    <p>False</p> Signup and view all the answers

    What is a loadable kernel module?

    <p>A loadable kernel module is a core component of an operating system that is separate and can be loaded as needed within the kernel.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of hybrid operating systems?

    <p>Using only monolithic kernels</p> Signup and view all the answers

    What programming environment is used in Apple's iOS for app development?

    <p>Cocoa Touch Objective-C API</p> Signup and view all the answers

    Android is developed by the Open Handset Alliance and is open source.

    <p>True</p> Signup and view all the answers

    What does DTrace in Solaris allow?

    <p>Live instrumentation on production systems</p> Signup and view all the answers

    What is the purpose of the SYSGEN program in operating system generation?

    <p>The SYSGEN program obtains hardware configuration information to build a system-specific compiled kernel.</p> Signup and view all the answers

    What initializes the execution of an operating system when power is turned on?

    <p>Execution starts at a fixed memory location using the firmware ROM.</p> Signup and view all the answers

    What does the bootstrap loader do?

    <p>It loads the kernel into memory and starts it</p> Signup and view all the answers

    Study Notes

    Introduction to Operating Systems

    • Operating System (OS) serves as an intermediary between users and computer hardware.
    • Goals of an OS: execute user programs, enhance user convenience, and optimize hardware utilization.

    Computer System Components

    • Four key components: hardware (CPU, memory, I/O), OS, application programs (e.g., word processors, databases), and users (people or machines).
    • OS controls and coordinates hardware among applications and users.

    User Perspectives on OS

    • User requirements: convenience, ease of use, and performance over resource utilization.
    • Different environments: shared systems (mainframes), dedicated workstations, and resource-constrained devices (handhelds).

    OS Functions

    • OS acts as an allocator of resources, managing demands and ensuring fair usage.
    • It controls program execution to prevent errors and improper uses.
    • Definitions of OS vary; generally, it comprises the kernel and accompanying system and application programs.

    System Startup

    • Bootstrapping initializes all system aspects, loading the OS kernel from firmware stored in ROM/EPROM.

    Computer Organization and Operation

    • Modern systems have multiple CPUs and device controllers connected via a bus, enabling concurrent operations.
    • Device controllers manage data flow between I/O devices and main memory.

    Interrupts

    • Interrupts transfer control to the OS and require saving the CPU's state.
    • Types of interrupts: hardware interrupts and software-generated traps (e.g., program errors).
    • OS is driven by interrupts, responding to various device and user requests.

    I/O Operations and Structure

    • Control returns to the user program only upon I/O completion unless otherwise specified.
    • Device-status tables track each I/O device status.

    Storage Structures

    • Main memory is volatile and provides direct access to the CPU, whereas secondary storage (e.g., hard disks) offers larger, non-volatile capacity.
    • Storage hierarchy organized by speed, cost, and volatility with caching as a vital mechanism for performance.

    Direct Memory Access (DMA)

    • Enables high-speed data transfers directly between devices and memory, minimizing CPU intervention and reducing interrupts.

    Computer-System Architecture

    • Predominantly single processor systems, with increasing adoption of multiprocessor and multi-core systems for better performance and reliability.
    • Two multiprocessor types: asymmetric (dedicated tasks) and symmetric (shared tasks).

    Clustering Systems

    • Multiple interconnected systems provide high availability and fault tolerance.
    • Types include asymmetric clustering (hot-standby) and symmetric clustering (active monitoring).

    OS Structure and Operations

    • Multiprogramming increases CPU usage by organizing jobs, while timesharing enables multiple user interactions.
    • Dual-mode operation protects the OS from user processes.
    • CPU timer counters prevent resource hogging by interrupting processes after a designated time.

    Process Management

    • A process is an executing program requiring system resources: CPU, memory, I/O.
    • Multi-threading allows concurrent execution within a single process, enhancing efficiency.

    Memory Management

    • Essential for program execution; it ensures that necessary instructions and data reside in memory during runtime.### Memory Management
    • Manages memory allocation and tracks usage to optimize CPU performance and user experience.
    • Activities include tracking memory usage, deciding data movement in and out of memory, and allocating/deallocating memory.

    Storage Management

    • Provides a logical abstraction of physical storage, presenting files instead of raw data.
    • Controlled by device drivers with varying access speeds, capacities, and methods (sequential/random).

    File-System Management

    • Files organized into directories with access control for security.
    • OS tasks include creating/deleting files, mapping storage, and backing up data.

    Mass-Storage Management

    • Disks store data not fitting in main memory or requiring long-term retention.
    • Key activities: managing free space, storage allocation, and disk scheduling.
    • Tertiary storage includes optical media and magnetic tapes, requiring management despite slower speeds.

    Data Migration

    • Critical in multitasking environments to ensure the most recent data is accessed.
    • In multiprocessor systems, cache coherence is essential to keep data synchronized across CPUs.
    • Distributed environments complicate data consistency with multiple copies of information.

    I/O Subsystem

    • Hides hardware complexities from users; manages data transfer and device operations.
    • Responsible for buffering, caching, and spooling to optimize input/output processes.

    Protection and Security

    • Protection mechanisms control access to resources by processes/users.
    • Security focuses on defense against various attacks (e.g., denial-of-service, malware).
    • User identification through unique IDs and group IDs that regulate access permissions.

    Kernel Data Structures

    • Utilizes standard programming structures like linked lists and binary search trees for efficiency.

    UNIX Example

    • A multitasking OS using fork() to create processes and exec() to load programs.
    • Processes exit with a status code indicating success (0) or error (non-zero).

    System Programs

    • Facilitate program development and execution through several functions: file manipulation, status information, programming support, and communication mechanisms.

    Operating System Design and Implementation

    • Aimed at balancing user goals (convenience, reliability) and system goals (flexibility, maintenance).
    • Separation of policy (what to do) from mechanism (how to do it) enhances adaptability.

    Implementation Variations

    • Early OSes developed in assembly; modern implementations primarily in C/C++.
    • Mix of languages enhances portability but can affect performance.

    Operating System Structures

    • General-purpose OS may follow various structures: simple (MS-DOS), complex (UNIX), layered, or microkernel (Mach).
    • Layered systems allow modular development, while microkernels enhance reliability and security but may introduce overhead.

    Modules

    • Modern OSes use loadable kernel modules for flexibility and dynamic functionality.
    • Interfaces facilitate communication among separate components.

    Hybrid Systems

    • Combine features from multiple architectures for optimized performance and security.
    • Examples include Linux/Solaris (monolithic, modular) and Mac OS X (layered, microkernel hybrid).

    Mobile Operating Systems

    • iOS, structured on Mac OS X, incorporates touch interfaces and cloud services.
    • Android, based on a modified Linux kernel, provides power management and a Java-based development environment.

    Operating-System Debugging

    • Involves identifying and resolving software bugs with log files and memory dumps.
    • Performance tuning executed via trace listings and profiling to analyze and enhance efficiency.### Performance Tuning
    • Performance improvement involves removing bottlenecks within an operating system (OS).
    • The OS should provide tools for measuring and displaying system behavior.
    • Examples of such tools include the “top” program on Unix-based systems and Task Manager on Windows.

    DTrace

    • DTrace is a powerful tool available on Solaris, FreeBSD, and Mac OS X for live instrumentation on production systems.
    • Probes within DTrace activate when specific code is executed, capturing state data for analysis.
    • An example use case is tracking the XEventsQueued system call as it transitions from the libc library to the kernel and back.

    DTrace Applications (Cont.)

    • DTrace can record the duration (in nanoseconds) that each process with UserID 101 spends in a running state on the CPU.

    Operating System Generation

    • Operating systems are created to function across a variety of machine types, requiring specific configurations for individual hardware setups.
    • The SYSGEN program collects hardware configuration data to build a tailored, system-specific kernel that can be more efficient than one-size-fits-all kernels.

    System Boot

    • System execution begins at a defined memory location upon power initialization, with firmware ROM containing the initial boot code.
    • A bootstrap loader, often stored in ROM or EEPROM, is essential for loading the OS into memory and initiating it.
    • Booting can be a two-step process where a boot block, loaded by ROM code, finds and loads the bootstrap loader from disk.
    • GRUB is a common bootstrap loader that provides options for selecting kernels from various disks and versions, facilitating multi-boot environments.
    • Once the kernel is loaded, the operating system becomes operational.

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    UNIT 1-21CSC202J- Operating System.ppt.pdf

    Description

    This quiz covers the fundamental concepts of Operating Systems as introduced in Unit I of the 21CSC202J course. Topics include computer-system organization, operating-system structure, process management, and open-source operating systems. Test your understanding of how operating systems function and their various components.

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