Laguna State Poly U: Platform Tech Module 3
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Questions and Answers

What does a program do unless its instructions are executed by a CPU?

Nothing

What is a program in execution called?

A process

What is the purpose of Process Management?

To manage and control all the processes running on the system

What does PCB stand for?

<p>Process Control Block</p> Signup and view all the answers

Which of the following is not a Process state?

<p>Completed (C)</p> Signup and view all the answers

What is CPU Scheduling?

<p>The process of determining which process will own the CPU for execution while another process is on hold</p> Signup and view all the answers

What does the CPU scheduler do?

<p>It selects one of the processes in memory that are ready for execution</p> Signup and view all the answers

Which of the following is not a type of CPU scheduling?

<p>Least Recently Used (LRU) (E)</p> Signup and view all the answers

What is the difference between Preemptive and Non-Preemptive scheduling?

<p>In Preemptive scheduling, a higher priority process can interrupt a lower priority process, while in Non-Preemptive scheduling, the currently executing process runs until it completes or voluntarily releases the CPU.</p> Signup and view all the answers

What is the primary goal of a CPU scheduling algorithm?

<p>To maximize CPU utilization and minimize waiting time for processes</p> Signup and view all the answers

What is the purpose of Disk Scheduling?

<p>To effectively manage the order of I/O requests arriving for the disk.</p> Signup and view all the answers

What is not a benefit of Disk Scheduling?

<p>Increased CPU utilization (C)</p> Signup and view all the answers

Explain the concept of Seek Time and its importance.

<p>Seek Time is the time taken by the disk arm to move from its current position to the desired track where data is stored or retrieved. Minimizing Seek Time is crucial for improving disk performance.</p> Signup and view all the answers

What is Rotational Latency?

<p>Rotational Latency is the time it takes for the desired sector on the disk to rotate into a position where the read/write head can access it.</p> Signup and view all the answers

What is the formula for calculating Disk Access Time?

<p>Disk Access Time = Rotational Latency + Seek Time + Transfer Time</p> Signup and view all the answers

Explain the concept of Disk Response Time.

<p>Disk Response Time is the average time spent by each request waiting for the I/O operation.</p> Signup and view all the answers

What is the primary advantage of using FCFS (First-Come, First-Served) scheduling?

<p>Simplicity and fairness.</p> Signup and view all the answers

What potential drawback does FCFS have in terms of disk performance?

<p>It can lead to inefficient disk head movement, especially when requests are scattered across the disk.</p> Signup and view all the answers

What is the principle behind SSTF (Shortest Seek Time First)?

<p>The disk head services the request with the shortest seek time next.</p> Signup and view all the answers

What is the main advantage of SSTF?

<p>It typically reduces the average response time and increases throughput.</p> Signup and view all the answers

What is the potential drawback of SSTF?

<p>It can lead to starvation, where some requests may never be serviced if there are constantly closer requests arriving.</p> Signup and view all the answers

What is the key characteristic of SCAN Disk Scheduling?

<p>The disk head moves in one direction, servicing requests in that direction, and then reverses direction when it reaches the end of the disk.</p> Signup and view all the answers

What is the key benefit of using SCAN?

<p>It offers higher throughput and a more uniform wait time for requests compared to SSTF.</p> Signup and view all the answers

What is the key difference between SCAN and C-SCAN?

<p>C-SCAN is a circular SCAN, meaning that after reaching the end of the disk, the disk head immediately jumps to the other end and continues scanning.</p> Signup and view all the answers

How does the LOOK algorithm differ from SCAN?

<p>In LOOK, the disk head only moves to the last request in the direction it is currently scanning, instead of going all the way to the end, and then reverses direction.</p> Signup and view all the answers

What is the fundamental difference between LOOK and CLOOK?

<p>LOOK moves back and forth across the disk, while CLOOK only goes to the last request in the current direction before reversing</p> Signup and view all the answers

What is the primary advantage of using a Round Robin scheduler?

<p>Its ability to provide fairness by giving each process a fixed amount of CPU time before moving to the next process.</p> Signup and view all the answers

What is the crucial factor that needs to be determined when implementing a Round Robin scheduler?

<p>The time quantum (q) which defines the slice of CPU time that each process receives before being preempted.</p> Signup and view all the answers

What is the major drawback of a Round Robin scheduler?

<p>It may not be optimal for processes with varying execution times, as a longer process could keep a short process waiting for a long period.</p> Signup and view all the answers

What characteristic of processes makes them well suited for Priority scheduling?

<p>Processes with varying priorities, where some processes are deemed more important than others.</p> Signup and view all the answers

What is a fundamental assumption behind Priority scheduling?

<p>Processes with higher priorities will remain in the ready queue until they are executed.</p> Signup and view all the answers

Explain the key concept of Shortest Job First (SJF) scheduling.

<p>SJF prioritizes the process with the shortest burst time, aiming to minimize the average waiting time.</p> Signup and view all the answers

What is the primary advantage of using SJF?

<p>It yields the shortest average waiting time for a given set of processes, making it an efficient method for batch systems.</p> Signup and view all the answers

What is the fundamental drawback of SJF?

<p>The actual burst time is rarely known beforehand, making it difficult to accurately implement SJF.</p> Signup and view all the answers

What is the core principle of Shortest Remaining Time First (SRTP) scheduling?

<p>The scheduler chooses the process with the shortest remaining time to complete its execution.</p> Signup and view all the answers

What is the primary objective of Disk Scheduling?

<p>Seek time minimization and efficient disk head movement.</p> Signup and view all the answers

What makes SRTP a preemptive algorithm?

<p>It can interrupt a currently executing process if a new process arrives with a shorter remaining burst time.</p> Signup and view all the answers

What are some of the key performance metrics for Disk Scheduling algorithms?

<p>These include Seek Time, Rotational Latency, Transfer Time, Disk Access Time, and Disk Response Time.</p> Signup and view all the answers

What is the primary advantage of using a preemptive scheduling algorithm?

<p>It allows for greater responsiveness by interrupting a process with a long execution time to allow a higher priority process or a process with a short execution time to be executed.</p> Signup and view all the answers

Flashcards

Program

A piece of code that can be executed by a computer. It represents a passive entity, containing instructions but not currently running.

Process

A program in execution. It represents an active entity using system resources to perform a specific task.

Process Control Block (PCB)

A data structure maintained by the OS for each process, containing information about the process's state, resources, and execution context.

Process State

A condition of a process at a specific instant of time. It describes the current state of a process.

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Process Creation

A process is created when a program is loaded into memory, ready to be executed.

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Process Termination

A process is terminated when its execution is completed, or when it encounters an error.

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Process Management

The job of the OS is to manage all the running processes of the system, including allocating resources and scheduling their execution.

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Thread

A unit of execution within a process. Multiple threads can exist within a single process, and they can execute concurrently.

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CPU Scheduling

The process of selecting which process will get access to the CPU for execution. The OS decides which process to run next.

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CPU Burst

The time a process spends using the CPU to execute instructions.

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I/O Burst

The time a process waits for I/O operations, such as disk read/write, to complete.

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Preemptive Scheduling

A type of CPU scheduling where a process can be interrupted and replaced by another process even if it hasn't finished its current task.

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Non-Preemptive Scheduling

A type of CPU scheduling where a process keeps using the CPU until it completes its task or explicitly yields the CPU.

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Burst Time

The time required by a process to complete its execution.

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Arrival Time

The time when a process enters the ready queue and is waiting for its turn to be executed.

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Finish Time

The time when a process finishes its execution and exits the system.

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Multiprogramming

The ability of the OS to manage multiple programs in memory concurrently, switching between them to keep the CPU busy.

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Waiting Time

The amount of time a process waits in the ready queue before getting access to the CPU.

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Response Time

The time from when a request is made to when the first response is produced.

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Turnaround Time

The total time from when a process is submitted to when it completes its execution.

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Interval Timer

A method used to ensure a process doesn't monopolize the CPU. When a specific process is allocated the CPU, a timer is set for a certain interval, and the process is interrupted after that interval.

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Dispatcher

A module in the OS responsible for giving control of the CPU to a specific process. It performs tasks like context switching and switching between user and kernel modes.

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Gantt Chart

A graphical representation of the scheduling of processes over time. It shows the execution timeline of each process and when they occupy the CPU.

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First Come First Served (FCFS)

A CPU scheduling algorithm that uses a First-In, First-Out (FIFO) approach. Processes are executed in the order in which they arrive in the ready queue.

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Shortest Job First (SJF)

A CPU scheduling algorithm that prioritizes executing the process with the shortest burst (execution) time first.

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Non-Preemptive Priority Scheduling

A non-preemptive priority scheduling algorithm where each process is assigned a priority, and processes with higher priority are executed first.

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Preemptive Priority Scheduling

A preemptive priority scheduling algorithm where a process with a higher priority can interrupt and replace a process with lower priority even if the lower priority process is currently running.

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Round Robin Scheduling

A CPU scheduling algorithm where each process gets a fixed amount of time (time quantum) to execute. After the time quantum expires, the process is preempted and another process gets its turn.

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Disk Scheduling

The process of managing I/O requests to the disk. The OS decides the order in which disk requests are served, aiming to optimize disk access time and throughput.

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Shortest Seek Time First (SSTF)

A disk scheduling algorithm that prioritizes serving the request with the shortest seek time (distance between the current head position and the requested track).

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First Come First Served (FCFS) (Disk Scheduling)

A disk scheduling algorithm that serves requests in the order they arrive in the queue.

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Study Notes

Laguna State Polytechnic University Self-Paced Learning Module, Platform Technologies, Module 3

  • This module is for educational use only.
  • Unauthorized reproduction, use, and dissemination are strictly prohibited.
  • The intellectual property within the module is protected under Republic Act 8293.
  • Fair use of copyrighted work is permitted for criticism, comment, news reporting, teaching, scholarship, and research.

Intellectual Property

  • The module is for educational purposes only.
  • Unauthorized reproduction, use, or dissemination is strictly prohibited.

Process and Disk Management

  • Students will understand process management and methodologies.
  • Students will analyze CPU algorithms.
  • Students will use different CPU algorithms.
  • Students will understand the concept of Disk Scheduling.
  • Students will analyze different disk scheduling algorithms.

Operating System and Process Management

  • A program executes instructions provided by a CPU.
  • A program in execution is called a process.
  • Operating systems manage system resources in a convenient and efficient manner..
  • Processes may need to share resources.
  • Resources needed by one process at one time can make systems inconsistent.

Difference between Program and Process

  • A program is a piece of code; it can be a single or a million lines of instructions.
  • A process is a program in execution.

Process Control Block (PCB)

  • Every process is represented by a PCB (also known as a task control block) in the operating system.
  • PCB includes process state, program counter, CPU registers and scheduling information.
  • It stores accounting and business information, memory management, I/O status.

Process Creation and Termination

  • Processes are created by other processes or system calls.
  • A process may terminate naturally after completing its execution.
  • A child process may be terminated by its parent, or if an error occurs.
  • Processes are terminated for excessive memory needs.

Process Thread

  • A thread is an execution unit within a process.
  • Threads can run concurrently.
  • Threads improve application performance using parallelism.

CPU Scheduling

  • CPU scheduling allocates the CPU to processes when the CPU is idle.
  • Scheduling is deciding which threads get access to resources in a given moment or period.
  • CPU utilization , throughput, turnaround time, waiting time , and response time are all considered.

CPU Burst, I/O Burst

  • CPU burst: Time a process uses the CPU to execute instructions.
  • I/O burst: Time a process needs to wait for an I/O operation to complete (e.g., writing to disk or waiting for network).

CPU Scheduling Methods

  • Preemptive Scheduling: Tasks are assigned priorities; higher priority tasks run first, potentially interrupting lower ones.
  • Non-preemptive Scheduling: One task uses CPU until it finishes or voluntarily yields control.

Scheduling Criteria

  • CPU Utilization (How often the CPU is being used)
  • Throughput (How much work is done by the processor per given time)
  • Turnaround time (time from submission to process completion)
  • Waiting time (time a process waits in the ready queue)
  • Response time (time from submitting a request to the first response)

Interval Timer

  • Is a method related to preemption that sets a timer.
  • Forcing process to yield the CPU before burst ends.

Dispatcher

  • The module that gives control of CPU back to a process.

Scheduling Algorithms

  • First Come, First Served (FCFS)
  • Shortest Job First (SJF)
  • Priority Scheduling
  • Round Robin (RR)

Disk Scheduling

  • Disk scheduling is scheduling I/O requests coming to the disk .
  • Multiple I/O requests may need to be scheduled
  • Large movements of the disk arm can make the process inefficient.
  • Criteria for Disk Scheduling: Fairness, throughput, and minimal travelling head time.
  • Algorithms: First Come, First Served (FCFS), Shortest Seek Time First (SSTF), SCAN, C-SCAN, LOOK, C-LOOK

Disk Scheduling Algorithms

  • First-Come-First-Served (FCFS)
  • Shortest Seek Time First (SSTF)
  • SCAN
  • C-SCAN
  • LOOK
  • C-LOOK

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LSPU Self-Paced Learning Module (SLM) - Module 3 - Process and Disk Management PDF

Description

This self-paced learning module from Laguna State Polytechnic University covers key concepts in platform technologies, including process and disk management. Students will analyze CPU algorithms and understand disk scheduling methods relevant to operating systems. Engage in this educational course to enhance your comprehension of essential computing principles.

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