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Day 01Part 16- Scheduling Queue in Operating System, Job Queue, Ready Queue and Device Queue.

Day 01Part 16- Scheduling Queue in Operating System, Job Queue, Ready Queue and Device Queue

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Day 01 โ€“ Part 16: Scheduling Queues in Operating System

Topic: Job Queue, Ready Queue, Device Queue
For: GATE / B.Tech / Operating System Fundamentals


What are Scheduling Queues?

In an operating system, scheduling queues are used to manage processes during their life cycle. At any time, a process is in one of several queues depending on its state.


Types of Scheduling Queues

1โƒฃ Job Queue

Example: When a process is created, it enters the job queue first.


2โƒฃ Ready Queue

Example: When a process has all the resources except CPU, it waits in the ready queue.

Key Point: Only one process gets CPU at a time; others wait here.


3โƒฃ Device Queue (I/O Queue)

Example: If a process needs to read from disk, it is moved to the diskโ€™s device queue.


Process State Transitions and Queues:

mermaid
flowchart LR
NEW[New Process] -->|Admitted| ReadyQ[Ready Queue]
ReadyQ -->|Dispatched| CPU
CPU -->|I/O Request| IOQ[Device Queue]
IOQ -->|I/O Complete| ReadyQ
CPU -->|Exit| Terminated

Summary Table:

Queue Managed by Purpose
Job Queue Long-term scheduler Holds all processes
Ready Queue Short-term scheduler Holds processes ready for CPU
Device Queue I/O scheduler Holds processes doing I/O

Quiz: Test Your Understanding

  1. A process is moved from the ready queue to CPU. What is this action called?

    • A) Interrupt

    • B) Dispatch

    • C) Admit

    • D) Block

  2. Which queue holds processes waiting for I/O?

    • A) Job Queue

    • B) Ready Queue

    • C) Device Queue

    • D) None


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Day 01Part 16- Scheduling Queue in Operating System, Job Queue, Ready Queue and Device Queue.

CSC 553 Operating Systems Types of Scheduling

Process Scheduling