COMSCI 2101 - PROCESSOR MANAGEMENT (PT1)

PROCESS

basic unit of execution in the operating system

PROCESS

the name we give to a program when it is running in memory.

PROGRAM

a compiled set of instructions that are stored in an executable
file.

PROCESS

the instance of this executable file that the operating system runs, along with its associated resources and current state of execution (e.g.,memory allocation,

JOB SCHEDULER
PROCESS SCHEDULER

The Processor Manager is made up of two sub-managers:

JOB SCHEDULER

High level scheduler

PROCESS SCHEDULER

Low level scheduler

JOB

We describe a collection of processes as a

JOB SCHEDULER

wants to ensure that all components of the operating system are busy, and there is NO COMPONENT that is IDLE.

BATCH JOBS

jobs that are CPU-bound

INTERACTIVE JOBS

jobs that have a lot of I/O operations

PROCESS CONTROL BLOCK

Every process has a field that records their current status, called the

HOLD

When the process is first passed to the Job Scheduler from the
operating system, its status is always set as

READY

When the Job Scheduler passes the process onto the Process
Scheduler, its status is always changed to

PROCESS SCHEDULER

Assigns the CPU to execute processes of those jobs placed on ready queue by Job Scheduler.

PROCESS SCHEDULER

- Determines which jobs will get CPU, when, and for how long.
- Decides when processing should be interrupted.
- Determines queues job should be moved to during execution.
- Recognizes when a job has concluded and should be terminated.

MIDDLE-LEVEL SCHEDULER

In a highly interactive environment there's a third layer
called

MIDDLE-LEVEL SCHEDULER

Removes active jobs from memory to reduce degree of
multiprogramming and allows jobs to be completed faster.

HOLD TO FINISH

When the jobs moves through the system and makes progress, it changes it's states from

1. HOLD
2. READY
3. RUNNING
4. WAITING
5. FINISHED

(JOB AND PROCESS STATUS)
When the job is being processed by the job manager and the
process manager, it is always in one of these 5 states:

HOLD STATE

When a user submits a job and it accepts the job, the job is put on ______ and placed in a queue.

READY STATE

A job is in ______ state when it's ready to run and waiting for the CPU.

RUNNING STATE

When a job is in _______ state, it is being executed.

WAITING STATE

When a job is in ________ state, it means that the job can't continue until a specified I/O operation is done or a resource is allocated.

FINISHED STATE

When a job is in _________ state, it means that the job is done and the output will be returned to the user.

PROCESS CONTROL BLOCK

data structure that contains basic info about the job

Queues

- use PCBs to track jobs.
- PCBs, not jobs, are linked to form
- ____________ must be managed by process scheduling policies and algorithms.