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Questions and Answers
What is the primary function of an operating system in a computer system?
What is the primary function of an operating system in a computer system?
Which of the following is NOT a major function of an operating system?
Which of the following is NOT a major function of an operating system?
Which component is responsible for managing the processes in an operating system?
Which component is responsible for managing the processes in an operating system?
What does memory management in an operating system involve?
What does memory management in an operating system involve?
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How does an operating system provide security to a computer system?
How does an operating system provide security to a computer system?
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What is one of the main goals of an operating system?
What is one of the main goals of an operating system?
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Which component is responsible for managing hardware utilization?
Which component is responsible for managing hardware utilization?
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How does an operating system act as a resource allocator?
How does an operating system act as a resource allocator?
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Which statement is true regarding how users perceive operating systems?
Which statement is true regarding how users perceive operating systems?
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What role does an operating system play in the prevention of errors?
What role does an operating system play in the prevention of errors?
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What is a characteristic feature of dedicated systems?
What is a characteristic feature of dedicated systems?
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What does the term 'kernel' refer to in operating systems?
What does the term 'kernel' refer to in operating systems?
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How is the performance of handheld computers typically optimized?
How is the performance of handheld computers typically optimized?
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What is NOT a typical component of a computer system?
What is NOT a typical component of a computer system?
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What describes users in the context of computer systems?
What describes users in the context of computer systems?
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What does increased reliability in computing systems typically ensure?
What does increased reliability in computing systems typically ensure?
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Which type of multiprocessing involves multiple nodes monitoring each other?
Which type of multiprocessing involves multiple nodes monitoring each other?
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In a clustered system, what role does the storage-area network (SAN) play?
In a clustered system, what role does the storage-area network (SAN) play?
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What is the primary goal of multiprogramming in an operating system?
What is the primary goal of multiprogramming in an operating system?
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What is the expected response time for a timesharing system?
What is the expected response time for a timesharing system?
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What happens during the transition from user mode to kernel mode?
What happens during the transition from user mode to kernel mode?
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What mechanism prevents a process from hogging system resources indefinitely?
What mechanism prevents a process from hogging system resources indefinitely?
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In which scenario would swapping occur?
In which scenario would swapping occur?
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Which characteristic is NOT associated with symmetric clustering?
Which characteristic is NOT associated with symmetric clustering?
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What is considered a proactive measure by operating systems against software errors?
What is considered a proactive measure by operating systems against software errors?
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What is the main purpose of the dual-mode operation in operating systems?
What is the main purpose of the dual-mode operation in operating systems?
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Which of the following best describes a process in a computing context?
Which of the following best describes a process in a computing context?
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When designing applications for high-performance computing (HPC) in clustered systems, what must be considered?
When designing applications for high-performance computing (HPC) in clustered systems, what must be considered?
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What is the primary role of the operating system in process management?
What is the primary role of the operating system in process management?
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What does a single-threaded process use to track the next instruction?
What does a single-threaded process use to track the next instruction?
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What is NOT a responsibility of memory management in an OS?
What is NOT a responsibility of memory management in an OS?
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What mechanism does the OS provide to prevent deadlocks between processes?
What mechanism does the OS provide to prevent deadlocks between processes?
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How does an OS typically organize files for user access?
How does an OS typically organize files for user access?
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Which of the following describes the role of the I/O subsystem in an OS?
Which of the following describes the role of the I/O subsystem in an OS?
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Which storage type typically has slower access speeds but is used for long-term data retention?
Which storage type typically has slower access speeds but is used for long-term data retention?
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Which of the following identifies the main purpose of storage management in an OS?
Which of the following identifies the main purpose of storage management in an OS?
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What is the primary function of protection mechanisms in an OS?
What is the primary function of protection mechanisms in an OS?
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What does the process of spooling in the I/O subsystem refer to?
What does the process of spooling in the I/O subsystem refer to?
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What is the function of cache coherency in a multiprocessor environment?
What is the function of cache coherency in a multiprocessor environment?
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What is the significance of reclaiming resources during process termination?
What is the significance of reclaiming resources during process termination?
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Which concept defines the potential for multiple processes to execute concurrently on a system?
Which concept defines the potential for multiple processes to execute concurrently on a system?
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What does the bootstrap program do during computer startup?
What does the bootstrap program do during computer startup?
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What is a key function of an interrupt in an operating system?
What is a key function of an interrupt in an operating system?
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In the context of I/O operations, what does a wait instruction do?
In the context of I/O operations, what does a wait instruction do?
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What purpose does the device-status table serve in an operating system?
What purpose does the device-status table serve in an operating system?
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How does a device controller communicate the completion of an operation to the CPU?
How does a device controller communicate the completion of an operation to the CPU?
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What defines a trap in operating systems?
What defines a trap in operating systems?
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What is the main advantage of Direct Memory Access (DMA) in I/O operations?
What is the main advantage of Direct Memory Access (DMA) in I/O operations?
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Which statement accurately describes the characteristics of main memory?
Which statement accurately describes the characteristics of main memory?
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What principle underlies the function of caching in computer systems?
What principle underlies the function of caching in computer systems?
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Why are interrupts disabled during the processing of another interrupt?
Why are interrupts disabled during the processing of another interrupt?
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Which characteristic does NOT apply to secondary storage?
Which characteristic does NOT apply to secondary storage?
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What is the role of a multiprocessor system?
What is the role of a multiprocessor system?
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How does the storage hierarchy organize different types of storage?
How does the storage hierarchy organize different types of storage?
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What is involved in the cache management process?
What is involved in the cache management process?
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Study Notes
What is an Operating System?
- An operating system acts as an intermediary between a user and the computer hardware.
- The goals of an operating system are:
- Execute user programs and make solving user problems easier.
- Make the computer system convenient to use.
- Use the computer hardware efficiently.
Computer System Structure
- A computer system is composed of four components:
- Hardware: Provides basic computing resources (CPU, memory, I/O devices).
- Operating System: Controls and coordinates the use of hardware amongst applications and users.
- Application Programs: Define how system resources are used to solve user computing problems (word processors, compilers, web browsers, etc.).
- Users: People, machines, or other computers interacting with the system.
Operating System Functions
-
Depends on the perspective:
- Users prioritize convenience and ease of use, not resource utilization.
- Shared computer systems need to satisfy all users.
- Dedicated systems (e.g., workstations) have dedicated resources but often use shared resources from servers.
- Handheld computers prioritize usability and battery life due to limited resources.
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Resource Allocator: Manages all resources and decides between conflicting requests for fair and efficient resource use.
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Control Program: Controls program execution to prevent errors and improper use of the computer.
Kernel in Operating System
- The kernel is the core of the operating system, always running.
- Everything else is either a system program (shipped with the OS) or an application program.
Computer Startup
- The bootstrap program, stored in ROM or EPROM (firmware), initializes the system at power-up or reboot.
- It loads and starts the execution of the operating system kernel.
Computer System Organization
- Components connect through a common bus:
- One or more CPUs.
- Device controllers.
- Shared memory.
- Concurrent execution of CPUs and devices compete for memory cycles.
Interrupt Handling
- Each device controller manages a specific device type and has a local buffer.
- CPU transfers data between main memory and local buffers.
- I/O happens between the device and the controller's local buffer.
- The device controller informs the CPU of completion through an interrupt.
Interrupt Architecture
- An interrupt transfers control to the interrupt service routine, typically through an interrupt vector that stores addresses of service routines.
- The interrupt architecture saves the address of the interrupted instruction.
- Incoming interrupts are disabled during interrupt processing to prevent loss.
- A trap, a software-generated interrupt, is triggered by errors or user requests.
- Operating systems are interrupt-driven.
I/O Structure
- Wait Instruction: The CPU idles until I/O completion, preventing simultaneous I/O processing.
- System Call: User requests the operating system to wait for I/O completion, allowing the CPU to continue processing other tasks.
- Device-Status Table: Contains information about each I/O device, including type, address, and state.
Direct Memory Access (DMA)
- Used for high-speed I/O devices that can transmit data at close to memory speeds.
- The device controller transfers data directly between buffer storage and main memory without CPU intervention.
Storage Structure
- Main Memory: Volatile memory that the CPU directly accesses. Offers random access.
- Secondary Storage: Nonvolatile storage with larger capacity, extends main memory.
- Magnetic Disks: Rigid platters covered with magnetic recording material. Surface is logically divided into tracks and sectors.
Storage Hierarchy
- Storage systems are organized based on speed, cost, and volatility.
-
Caching: Copying information into a faster storage system temporarily.
- Main memory can act as a cache for secondary storage.
Computer-System Architecture
- Most systems use a single general-purpose processor, but many have special-purpose processors.
-
Multiprocessor Systems: (parallel or tightly-coupled systems)
- Advantages:
- Increased throughput.
- Economy of scale.
- Increased reliability (graceful degradation or fault tolerance).
- Types:
- Asymmetric Multiprocessing: One processor is designated as the master, while others are slaves.
- Symmetric Multiprocessing: All processors are equal and can run any task.
- Advantages:
Clustered Systems
- Multiple systems (nodes) working together, often sharing storage via a storage-area network (SAN).
- Types:
- Asymmetric Clustering: One node in hot-standby mode.
- Symmetric Clustering: Multiple nodes run applications and monitor each other.
- Used for high-availability service, surviving failures.
- Some clusters focus on high-performance computing (HPC).
Operating-System Structure
-
Multiprogramming: Improves efficiency by organizing jobs (code and data), keeping the CPU busy.
- Subset of jobs is kept in memory.
- Job scheduling selects and runs a job.
- When waiting (e.g., for I/O), the OS switches to another job.
-
Timesharing (multitasking): CPU switches jobs frequently, enabling interactive computing.
- Each user has at least one program running in memory (a process).
- CPU scheduling manages multiple processes ready to run simultaneously.
- Swapping moves processes in and out of memory when they don't fit.
- Virtual memory allows execution of processes not fully loaded in memory.
Operating-System Operations
- Interrupts: Triggered by hardware, software errors (exceptions/traps), or process problems (infinite loops, modifications).
-
Dual-Mode Operation: Protects the OS and other system components.
- User Mode: Used for user programs.
- Kernel Mode: Used for OS code.
- Mode Bit: A hardware mechanism to differentiate between modes, only allowing privileged instructions in kernel mode.
- System Call: Switches from user mode to kernel mode.
Timer Interrupt Handling
- Prevents processes from hogging resources.
- Timer interrupt is set after a specific period.
- The OS decrements the timer counter.
- At zero, the timer interrupt triggers, allowing the OS to regain control or terminate exceeding processes.
Process Management
- A process is an active entity within a system that requires resources to execute.
- A process includes a program, CPU, memory, I/O, files, initialization data and more.
Process Management Activities
- An OS is responsible for creating and deleting both user and system processes, managing process synchronization and communication, and handling deadlocks.
Memory Management
- Memory management is the art of optimizing CPU utilization and computer response to users by determining what is in memory when.
- Memory management activities include:
- Tracking what parts of memory are in use and by whom.
- Deciding which processes and data to move in and out of memory.
- Allocating and deallocating memory space as needed.
Storage Management
- The OS provides a uniform logical view of information storage by abstracting physical properties to logical storage units (files).
- Files are usually organized into directories and can be accessed by authorized users.
Mass-Storage Management
- Mass-storage management is important for data that does not fit in main memory or data that needs to be kept for a long time.
- Disks are usually utilised for this data and proper management of this system is critical for computer speed.
- Mass-storage management activities include free-space management, storage allocation and disk scheduling, including tertiary storage.
I/O Subsystem
- The I/O subsystem is responsible for memory management of I/O, including buffering, caching, spooling and general device-driver interface.
Protection and Security
- Protection refers to mechanisms for controlling access of processes or users to specific resources defined by the OS.
- System security is the defense of the system against internal and external attacks, including denial-of-service, worms, viruses, identity theft, and theft of service.
- User identities (user IDs, security IDs) include a name and an associated number, one per user.
- User IDs are associated with files and processes to control access.
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Description
This quiz covers the basic concepts related to operating systems, including their functions, structure, and the components of a computer system. It highlights the role of operating systems as intermediaries between users and hardware, and how they enhance usability and efficiency.
