Operating System History and Computer Architecture
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What is the purpose of system calls in an operating system?

  • To manage the CPU instruction set.
  • To facilitate network connections without involving the kernel.
  • To allow user-level applications to directly access hardware.
  • To provide interaction between user programs and the kernel. (correct)

    • Which of the following accurately describes kernel mode?

  • It restricts the execution of CPU instructions.
  • It allows programs to access only user memory.
  • It permits direct access to all system resources. (correct)
  • It is a less privileged mode of operation.

    • Which protection ring is the least privileged in a typical operating system?

  • Ring 3 (correct)
  • Ring 2
  • Ring 1
  • Ring 0

    • In user mode, programs are restricted from which of the following actions?

    <p>Direct access to physical memory.</p> Signup and view all the answers

    Which statement about memory regions in an operating system is true?

    <p>User space is isolated from kernel space for security.</p> Signup and view all the answers

    What is typically the effect of executing an invalid instruction in kernel mode?

    <p>It may cause an irrecoverable system crash.</p> Signup and view all the answers

    How many protection rings are supported by most x86 CPUs?

    <p>2</p> Signup and view all the answers

    What restricts user-level processes in user mode from executing core system functions?

    <p>Limited access to CPU instructions</p> Signup and view all the answers

    What was the primary input method for the 2nd generation of computers?

    <p>Punch cards</p> Signup and view all the answers

    Which operating system was used in the 3rd generation of computers?

    <p>OS/360</p> Signup and view all the answers

    During which generation did hardware primarily consist of Integrated Circuits (ICs)?

    <p>3rd generation</p> Signup and view all the answers

    What was the primary output method for the 1st generation of computers?

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

    What technology was primarily used for input in the 4th generation of personal computers?

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

    Which statement correctly describes the evolution of operating systems?

    <p>No operating systems were present in the 1st and 2nd generation.</p> Signup and view all the answers

    What technology characterizes the hardware of the 4th generation of computers?

    <p>Large Scale Integration (LSI)</p> Signup and view all the answers

    In the context of computer architecture, what is an instruction?

    <p>An order for the computer to execute an operation</p> Signup and view all the answers

    What characterizes a Type-1 hypervisor?

    <p>It has direct access to hardware and runs on bare-metal.</p> Signup and view all the answers

    What is an example of a Type-2 hypervisor?

    <p>VMWare Workstation</p> Signup and view all the answers

    What must be enabled in BIOS settings for hypervisors to function correctly?

    <p>Virtualization Technology</p> Signup and view all the answers

    Which of the following describes the speed of context switches?

    <p>10 μs</p> Signup and view all the answers

    Which competency is NOT acquired according to the summary?

    <p>Differentiate between static and dynamic memory.</p> Signup and view all the answers

    What does Kernel Mode allow a program to do that User Mode does not?

    <p>Access hardware directly.</p> Signup and view all the answers

    What is the purpose of a system call in an operating system?

    <p>To allow user programs to request services from the kernel.</p> Signup and view all the answers

    Which of the following represents the slowest speed in data processing?

    <p>Transferring 1MB over the network</p> Signup and view all the answers

    What is the purpose of a hypervisor in virtualization?

    <p>To manage and execute virtual machines</p> Signup and view all the answers

    Which term refers to the computer that is virtualized in a virtualization setup?

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

    What type of hypervisor runs directly on the host hardware?

    <p>Type-1 Hypervisor</p> Signup and view all the answers

    Which one of the following statements about virtual machines (VMs) is true?

    <p>VMs are created as a software-based simulation.</p> Signup and view all the answers

    In the provided example, what function does System.currentTimeMillis() serve?

    <p>It returns the current time in milliseconds since the epoch.</p> Signup and view all the answers

    What is the primary role of the operating system kernel in relation to virtualization?

    <p>To manage hardware resources for VMs</p> Signup and view all the answers

    Which statement correctly differentiates between Type-1 and Type-2 hypervisors?

    <p>Type-2 runs on top of host operating systems, while Type-1 runs directly on hardware.</p> Signup and view all the answers

    What is a potential limitation of using virtualization?

    <p>It can lead to resource contention among virtual machines.</p> Signup and view all the answers

    What is the primary role of a system call during its execution?

    <p>It interrupts the user process and transfers control to the kernel.</p> Signup and view all the answers

    In the provided C example, what does the line time_t current_time = time(NULL); represent?

    <p>A system call that fetches the current time since the Unix epoch.</p> Signup and view all the answers

    What is the main consequence of the 2024 CrowdStrike incident?

    <p>A faulty update in software running in Kernel Mode causing significant financial damage.</p> Signup and view all the answers

    What does the Kernel Mode include compared to User Mode?

    <p>Greater access to hardware and system resources.</p> Signup and view all the answers

    What happens after the implementation of a system call finishes execution?

    <p>The results are stored in memory and control returns to the user process.</p> Signup and view all the answers

    Which of the following best describes 'User Space'?

    <p>The section of memory allocated for user processes to execute.</p> Signup and view all the answers

    What is encoded in the register during a system call?

    <p>The system call code.</p> Signup and view all the answers

    How is control returning to the user process after completing a system call?

    <p>By executing the TRAP instruction.</p> Signup and view all the answers

    Study Notes

    Operating System History

    • First-generation computers (1945-1955) used relays and vacuum tubes, relying on plugboards for input and printers for output.
    • Second-generation computers (1955-1965) transitioned to transistors, with punch cards and printers for I/O.
    • Third-generation computers (1965-1980) featured integrated circuits (ICs), adopted punch cards and tape drives for input and output.
    • Fourth-generation computers (1980-present) encompassed personal computers, utilizing large-scale integration (LSI), floppy disks, CD-ROMs, USB, and networks for input, and printers, monitors, and displays for output.

    Computer Architecture

    • A computer is a digital electronic machine that can be programmed to automatically execute sequences of arithmetic and logical operations.
    • Instructions given to the computer to execute operations are called programs.
    • Programs encompass tasks like creating files, retrieving system time, reading from USB devices, and transferring data over networks.
    • System calls are functions that interact with the operating system's kernel.
    • Device drivers are specialized programs that allow the operating system to communicate with hardware components.

    Protection Rings

    • Protection rings are hierarchical layers in the CPU architecture that implement restrictions on the set of instructions allowed to execute.
    • These rings help ensure safe execution by isolating core system functions from user-level processes.
    • x86 CPUs (Intel, AMD) support four rings (0-3), but most operating systems only implement two: ring 0 (kernel mode) and ring 3 (user mode).

    Kernel Mode and User Mode

    • Kernel mode is the most privileged operating mode, allowing direct access to all system resources including memory and hardware.
    • Programs running in Kernel Mode can potentially crash the system, leading to an irrecoverable halt.
    • User mode is a less privileged mode, limiting code execution's access to system resources (hardware and primary memory).
    • Most executed code runs in user mode, using a subset of available CPU instructions.
    • User mode programs depend on system calls to interact with hardware components.

    Kernel Space and User Space

    • Kernel space is the memory region where the operating system operates.
    • User space is the memory region used for user programs.
    • It's important to distinguish between kernel mode/space and user mode/space as they refer to different aspects of program execution and memory allocation.

    System Calls

    • System calls are functions that allow user-level processes to access kernel services and hardware resources.
    • When a user process needs to perform an action requiring privileged access, it makes a system call.
    • The system call is trapped by the operating system kernel, which interprets its code and executes the corresponding service.

    Virtualization

    • Virtualization is the process of creating a software-based simulation of something, such as virtual computer hardware, networks, or operating systems.
    • A virtual machine (VM) represents a software-based simulation of a computer.
    • A hypervisor is the software that manages and executes virtual machines.
    • The computer running the hypervisor is known as the host machine, and the virtualized computer is referred to as the guest machine.

    Hypervisor Types

    • Type-1 hypervisors (bare-metal hypervisors) run directly on the hardware, providing a platform for virtual machines to operate on top of it.
    • Type-2 hypervisors (hosted hypervisors) run within a host operating system, leveraging the host system's kernel to access hardware resources.

    Speed Comparison

    • Referencing registers is the fastest operation, taking 1 nanosecond (10-9 seconds).
    • Accessing main memory requires slightly more time, taking 10 nanoseconds (10-8 seconds).
    • System calls take 1 microsecond (10-6 seconds) for execution.
    • Context switching requires 10 microseconds (10-5 seconds).
    • Reading 1 bit from a solid-state drive (SSD) takes 100 microseconds (10-4 seconds), while reading from a hard disk drive (HDD) takes 10 milliseconds (10-2 seconds).
    • Transferring 1 megabyte (MB) over the network takes 1 second (100 seconds).

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    02_fundamentals.pdf

    Description

    Explore the evolution of operating systems and computer architecture through the generations. This quiz covers the key advancements from first-generation computers to the fourth generation, along with the fundamentals of how computers execute programs. Test your knowledge of the technological progression and functional components of modern computing.

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