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Questions and Answers
What is the primary function of the operating system as a resource allocator?
What is the primary function of the operating system as a resource allocator?
Which component controls the execution of user programs to prevent errors?
Which component controls the execution of user programs to prevent errors?
How does the bootstrap program function when the computer is powered up?
How does the bootstrap program function when the computer is powered up?
What occurs when a hardware-generated interrupt is signaled?
What occurs when a hardware-generated interrupt is signaled?
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What best describes the relationship between the kernel and system programs?
What best describes the relationship between the kernel and system programs?
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What is the role of the memory controller in a computer system?
What is the role of the memory controller in a computer system?
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Which of the following is NOT a component of computer system organization?
Which of the following is NOT a component of computer system organization?
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Which statement best describes application programs in relation to the operating system?
Which statement best describes application programs in relation to the operating system?
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What is the primary purpose of an interrupt vector in a computer architecture?
What is the primary purpose of an interrupt vector in a computer architecture?
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Which statement accurately describes the nature of main memory (RAM)?
Which statement accurately describes the nature of main memory (RAM)?
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In the context of instruction execution, what is the correct order of operations?
In the context of instruction execution, what is the correct order of operations?
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What is a significant limitation of main memory in a computer system?
What is a significant limitation of main memory in a computer system?
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Which statement correctly describes the role of caches in computer systems?
Which statement correctly describes the role of caches in computer systems?
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What is the primary function of a device controller in a computer system?
What is the primary function of a device controller in a computer system?
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Which type of memory technology can be changed but not frequently?
Which type of memory technology can be changed but not frequently?
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What does cache coherency ensure in a computer system?
What does cache coherency ensure in a computer system?
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What is the primary purpose of dual-mode operation in operating systems?
What is the primary purpose of dual-mode operation in operating systems?
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Which mode of operation is designated for user-defined code execution?
Which mode of operation is designated for user-defined code execution?
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What function does a timer serve in an operating system?
What function does a timer serve in an operating system?
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Which of the following describes the role of Virtual Machine Manager (VMM) in multi-mode operation?
Which of the following describes the role of Virtual Machine Manager (VMM) in multi-mode operation?
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What is a characteristic of privileged instructions within an operating system?
What is a characteristic of privileged instructions within an operating system?
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How did computing systems evolve from traditional mainframes?
How did computing systems evolve from traditional mainframes?
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What are batch systems primarily characterized by?
What are batch systems primarily characterized by?
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What is a common input device used in batch systems?
What is a common input device used in batch systems?
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What is the main advantage of Direct Memory Access (DMA) over traditional I/O operations?
What is the main advantage of Direct Memory Access (DMA) over traditional I/O operations?
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Which of the following statements correctly describes a single processor system?
Which of the following statements correctly describes a single processor system?
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What happens when the device controller generates an interrupt during I/O operations?
What happens when the device controller generates an interrupt during I/O operations?
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Which component is primarily responsible for determining the action to take based on loaded registers in I/O operations?
Which component is primarily responsible for determining the action to take based on loaded registers in I/O operations?
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What is one primary disadvantage of using traditional I/O operations for bulk data movement?
What is one primary disadvantage of using traditional I/O operations for bulk data movement?
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Which of the following best describes a multiprocessor system?
Which of the following best describes a multiprocessor system?
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In which situation is a special-purpose processor typically used?
In which situation is a special-purpose processor typically used?
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What is an essential characteristic of a multiprocessor system that increases its reliability?
What is an essential characteristic of a multiprocessor system that increases its reliability?
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What is a primary characteristic of client-server computing?
What is a primary characteristic of client-server computing?
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What distinguishes peer-to-peer (P2P) systems from client-server systems?
What distinguishes peer-to-peer (P2P) systems from client-server systems?
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Which statement about virtualization is true?
Which statement about virtualization is true?
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What types of cloud services can be categorized into public, private, or hybrid clouds?
What types of cloud services can be categorized into public, private, or hybrid clouds?
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Which of the following best describes the role of a file server?
Which of the following best describes the role of a file server?
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How is cloud computing payment structured?
How is cloud computing payment structured?
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What potential disadvantage is associated with traditional client-server systems?
What potential disadvantage is associated with traditional client-server systems?
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What is one of the main features of a hybrid cloud?
What is one of the main features of a hybrid cloud?
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Study Notes
Computer System Components
- Hardware provides the basic computing resources.
- Application programs define how resources are used.
- Operating system controls the hardware and coordinates its use.
Operating System Views
- Operating systems can act as resource allocators by managing resources and assigning them to programs and users.
- Operating systems can act as control programs by managing I/O devices and the execution of user programs to prevent errors or misuse.
Kernel and System Programs
- An operating system comprises the kernel and system programs.
- The kernel runs continuously.
- System programs are associated with the operating system.
- Application programs are not associated with the operating system.
Computer System Organization
- The system bus connects all system components.
- Each device controller manages a specific type of device.
- The CPU and device controllers can execute in parallel.
- The memory controller synchronizes access to the shared memory.
Bootstrap Program
- This program resides in ROM or EEPROM and is also known as firmware.
- It runs when the computer is powered up or rebooted.
- It initializes the system, including the CPU and memory.
- It locates the kernel, loads it into memory, and begins its execution.
Interrupts
- Interrupts signal the occurrence of events.
- A hardware interrupt signals the CPU.
- A software interrupt (or trap) occurs when a system call is executed.
- Each interrupt has a service routine (or handler) which is executed when the interrupt occurs.
- The interrupt vector, stored in low memory, contains the addresses of interrupt service routines.
Storage Structure
- ROM cannot be changed.
- EEPROM can be changed, but not frequently.
- Main memory (RAM) is implemented as DRAM.
- The CPU can only load instructions from main memory.
- The CPU interacts with RAM using load or store instructions.
- Load instructions move data from RAM to a CPU register.
- Store instructions move data from a CPU register to RAM.
Secondary Storage
- Main memory cannot permanently store all programs and data.
- RAM is often too small to store necessary programs and data.
- RAM is volatile, meaning it loses its contents when power is off.
- Secondary storage extends main memory, allowing for permanent data storage.
Caching
- Caches can be used to improve access time or transfer rate.
- Caching involves using high-speed memory to store recently-accessed data, assuming it will be needed again soon.
- Cache coherence ensures that updates to data in a cache are reflected immediately in other copies of that data.
I/O Structure
- Computer systems consist of CPUs and multiple device controllers connected by a common bus.
- Each device controller manages a specific type of device.
- Device controllers have local buffer storage and control registers.
- Device controllers transfer data between peripheral devices and their local buffer storage.
- The operating system provides device drivers which communicate with device controllers and provide a uniform interface to devices.
I/O Operation
- The device driver loads registers within the device controller.
- The device controller determines the action based on the registers.
- The device controller transfers data between the device and its local buffer.
- The device controller generates an interrupt to inform the device driver.
- The device driver returns control to the operating system, optionally returning data if the operation was a read. Device drivers also return status information.
Direct Memory Access
- This method allows the device controller to transfer a block of data directly between its local buffer and main memory, without CPU intervention.
- Only one interrupt per block signals the device driver, instead of an interrupt per byte.
- While the device controller transfers data, the CPU can perform other tasks.
Computer System Architecture
- These systems can be classified as single processor, multiprocessor, or clustered.
Single Processor Systems
- A general-purpose processor executes a complete instruction set and can run user processes.
- Special-purpose processors have a limited instruction set and cannot run user processes.
- Single processor systems have only one general-purpose processor.
Multiprocessor Systems
- These systems have two or more general-purpose processors that communicate closely, sharing resources like the bus, clock, memory, and peripherals.
- These systems are also known as parallel systems or tightly-coupled systems.
- They are commonly found in servers and now on mobile devices like smartphones and tablets.
Advantages of Multiprocessor Systems
- Increased throughput, as more processors complete more work in less time.
- Economy of scale, as sharing peripherals, storage, and power supplies reduces costs.
- Increased reliability, as the system remains operational even if one processor fails.
Clustered Systems
- These systems consist of multiple computers connected via a network.
- They can work together to provide high availability, load balancing, and increased throughput.
- Each computer has its own OS and can communicate through message passing.
Operating System Operations
- Operating systems utilize dual mode and multimode operations, along with timers.
Dual-Mode Operation
- Protects the operating system from errant user programs.
- Two modes exist: user mode and kernel mode (also known as supervisor mode, system mode, or privileged mode).
- User-defined code executes in user mode.
- Only the operating system can execute in kernel mode.
- A mode bit indicates the current mode: kernel (0) or user (1).
- Instructions that could cause harm are privileged.
- Privileged instructions can only be executed in kernel mode, by the OS.
Multi-Mode Operation
- The concept of modes can be extended beyond two.
- A virtualized CPU can have a third mode for the Virtual Machine Manager (VMM).
- VMM mode has more privileges than user mode, but fewer than kernel mode.
- VMM requires these privileges to manage and create virtual machines.
- Different modes are sometimes used by various kernel components.
Timer
- Prevents a user program from running for too long.
- A timer can be set to interrupt the system after a specific time.
- Timers are often implemented using a fixed-rate clock and a counter.
- The OS sets the counter before handing control over to a user program.
- The counter decrements each time the clock ticks.
- When the counter reaches zero, an interrupt occurs, returning control to the OS.
- The OS can treat the interrupt as a fatal error or allow the program more time.
Computing Environment
- Computing environments include traditional computing, virtualization, mobile computing, cloud computing, distributed computing, and real-time embedded systems.
Traditional Computing
- Early computer systems were mainframe computers, primarily used by large organizations.
- Mainframes evolved from batch systems to multiprogramming systems to time-sharing systems.
- Desktop computers were later introduced and gained popularity.
Batch Systems
- Jobs were processed in bulk, one after another.
- Input devices were card readers and tape drives.
- Output was printed by line printers and a memory dump.
- The operating system was a resident monitor for automatic job sequencing.
Distributed Computing
- This approach uses multiple physically separated systems to solve large problems.
- It can take the form of client-server computing or peer-to-peer computing.
Client-Server Computing
- A distributed system model where server systems fulfill client system requests.
- Servers can be compute-servers or file-servers.
- File servers allow clients to create, update, read, and delete files.
- Compute servers process client requests, execute actions, and return results.
Peer-to-Peer Computing
- Another model of distributed computing.
- A node joins the peer-to-peer system.
- All nodes are peers, each acting as a server when providing services or a client when requesting services.
- This model offers an alternative to client-server systems where the server is a bottleneck.
Virtualization
- Allows for the creation of virtual machines that act like real computers.
- A single computer (host) can run multiple virtual machines (guests).
- The host and guests share resources, but each has its own operating system.
- The virtual machine manager manages guest machines, their resource use, and protects them from each other.
Cloud Computing
- Provides computing as a service, with users paying based on usage.
- Uses virtualization to run millions of virtual machines on thousands of servers.
- Cloud services can be public, private, or hybrid.
- Public clouds are available to anyone through the internet.
- Private clouds are owned and used only by a company.
- Hybrid clouds combine public and private cloud components.
- Cloud services can provide infrastructure, platform, or application as a service.
- Software as a service (SaaS) provides applications (e.g., Google Docs).
- Platform as a service (PaaS) provides a software stack (e.g., Google Firebase).
- Infrastructure as a service (IaaS) provides servers or storage over the internet.
Mobile Computing
- Involves devices like smartphones, tablets, and laptops with wireless connectivity.
- Operating systems in these devices are designed to be lightweight and efficient.
- They support battery-efficient features, touch-screen interfaces, and mobile internet browsing.
Real-Time Embedded Systems
- Used in situations where real-time performance is crucial.
- They often have strict timing constraints and are commonly found in industrial equipment, medical devices, and automotive systems.
- They often have a dedicated operating system tailored to the application's specific requirements.
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Description
Explore the fundamental components of computer systems, including hardware, application programs, and operating systems. This quiz delves into how these elements interact, manage resources, and operate efficiently within a computer. Understanding these concepts is crucial for anyone delving into computer science.
