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Questions and Answers
What is the purpose of system calls in an operating system?
Which of the following accurately describes kernel mode?
Which protection ring is the least privileged in a typical operating system?
In user mode, programs are restricted from which of the following actions?
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Which statement about memory regions in an operating system is true?
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What is typically the effect of executing an invalid instruction in kernel mode?
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How many protection rings are supported by most x86 CPUs?
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What restricts user-level processes in user mode from executing core system functions?
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What was the primary input method for the 2nd generation of computers?
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Which operating system was used in the 3rd generation of computers?
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During which generation did hardware primarily consist of Integrated Circuits (ICs)?
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What was the primary output method for the 1st generation of computers?
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What technology was primarily used for input in the 4th generation of personal computers?
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Which statement correctly describes the evolution of operating systems?
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What technology characterizes the hardware of the 4th generation of computers?
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In the context of computer architecture, what is an instruction?
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What characterizes a Type-1 hypervisor?
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What is an example of a Type-2 hypervisor?
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What must be enabled in BIOS settings for hypervisors to function correctly?
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Which of the following describes the speed of context switches?
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Which competency is NOT acquired according to the summary?
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What does Kernel Mode allow a program to do that User Mode does not?
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What is the purpose of a system call in an operating system?
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Which of the following represents the slowest speed in data processing?
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What is the purpose of a hypervisor in virtualization?
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Which term refers to the computer that is virtualized in a virtualization setup?
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What type of hypervisor runs directly on the host hardware?
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Which one of the following statements about virtual machines (VMs) is true?
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In the provided example, what function does System.currentTimeMillis() serve?
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What is the primary role of the operating system kernel in relation to virtualization?
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Which statement correctly differentiates between Type-1 and Type-2 hypervisors?
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What is a potential limitation of using virtualization?
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What is the primary role of a system call during its execution?
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In the provided C example, what does the line time_t current_time = time(NULL);
represent?
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What is the main consequence of the 2024 CrowdStrike incident?
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What does the Kernel Mode include compared to User Mode?
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What happens after the implementation of a system call finishes execution?
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Which of the following best describes 'User Space'?
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What is encoded in the register during a system call?
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How is control returning to the user process after completing a system call?
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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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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.