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

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Here is a comprehensive breakdown of:

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Day 01 – Part 16: Scheduling Queues in Operating System

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

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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.

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Types of Scheduling Queues

1⃣ Job Queue

• Contains all processes in the system.

• Includes processes that are:

  • New (not yet admitted)

  • Waiting for CPU

  • Performing I/O

• Think of it as the master list of all jobs submitted to the OS.

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

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2⃣ Ready Queue

• Holds all processes that are ready to execute but are waiting for CPU.

• Managed by the short-term scheduler.

• These are loaded into main memory (RAM).

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.

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3⃣ Device Queue (I/O Queue)

• Contains processes waiting for an I/O device (printer, disk, etc.).

• Each I/O device has its own queue.

• Handled by the device scheduler.

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

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Process State Transitions and Queues:

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Summary Table:

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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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GATE Tip:

• Questions often ask “Which queue does a process move to after an I/O request?”

  • Answer: Device Queue

• Also expect diagrams, state transitions, and MCQs on scheduler types.

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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