os types.ppt

7/27/2019 os types.ppt

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Operating System Fundamentals

Dr. Ashraf Said

Math. & Comp. Sc. Dept.Faculty of Science

Alexandria University

Lecture 1 : Introduction and Concepts


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Outline

What is an Operating System? Types of Computer Systems Simple Batch Systems

Multi-programmed Batched Systems

Time-Sharing Systems

Personal-Computer Systems

Parallel Systems

Distributed Systems Real-Time Systems

Handheld Systems


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What is an Operating System?

A software that controls the hardware.

Processors, storage, input/output devices,

communication devices and data.

A software that manages the hardware.

A software that acts as a resources allocator.
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How Can We Define Operating

System?Operating System (OS) is a program that

controls the execution of application

programs. It is also defined as being themean through which controlling of allocation

and usage of hardware resources and

coordinating of all software activities within acomputer is done.


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Where Can an OS Fit?


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Operating System Objectives

Convenience: Makes the computer more convenient to use.

Ease of Communication: Between Computer and user through a friendly

user interface. Among system components.

Abstraction: Hardware-independent programming model.

Efficiency: Allows computer system resources to be used in

an efficient manner.


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Operating System Objectives (contd)

Monitoring and Alerting: Monitors and alerts failures and problems.

Ability to Evolve:

Permit effective development, testing, and introduction of

new system functions without interfering with the services.

Protection:

A layer of security is to be added to ensure that a certain

level of security is maintained to protect users data.

Increasing performance: Maximizing the throughput and Minimizing time needed to

execute command.


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Services Provided by the Operating

System Program development: Such as editors and

debuggers.

Program execution:

Load program and data, initialize environment. Access to I/O devices:

Attempt to read from and write to the ports and units.

Controlled access to data: Access protection.

System access: User authentication.


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System (contd) Error detection and response:

In case of error occurring, an error message

should be displayed.

Internal and external hardware errors: Memory error.

Device failure.

Software errors: Arithmetic overflow.

Access forbidden memory locations.


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System (contd) Accounting:

Collect statistics.

Monitor performance.

Is used to anticipate future enhancements?

Is usedfor billing users?


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Functions of an Operating System on a

Network

1. Sharing H/W among users.

2. Allowing users to share data.

3. Preventing users from interfering with oneanother.

4. Scheduling resources among users.

5. Organizing data forsecure and rapidaccess.

6. Handling network communications.


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Components of Computer System Input devices

Processing devices (Central Processing Unit) Output devices

Storage devices

Applications software

Word Processing Spreadsheet - Database

System software

Operating System - Utilities Users, orend users, are the people in the computing environment

who need the output that computer systems produce. Programmers are the people whose job it is to write programs to

supply this information.


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Layers of Computer System


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Computer-System Operation I/O devices and the CPU can

execute concurrently.

Each device controlleris

responsible of a particular

device type.

Each device controller has alocal buffer(memory).

CPU moves data from/to main memory to/from local buffers

I/O is from the device to local buffer of controller.


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Storage-Device Hierarchy

Storage systems organized in

hierarchy.

Speed

Cost

Volatility


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What is a Kernel?

Module Kernel is responsiblefor:

Memory allocation.

Garbage collection Object finalization

Module termination

Interfacing to theunderlying operating

system, and clock functions


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Types of Computer Systems

Simple Batch Systems

Multi-programmed Batched Systems

Time-Sharing Systems

Personal-Computer Systems Parallel Systems

Distributed Systems

Real-Time Systems Handheld systems


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Simple Batch System

Runs only one job at a time.

Smoothed transition between jobs to getmaximum utilization.

Programs/data submitted in groups or

batches.


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Multi-programmed Batch System

Usesjob scheduling to increase resources

utilization.

Stores more than one program in memory.

Based on the fact that any one job rarely

utilizes all computer resources.

When one job is waiting for an I/O, other can

use CPU and/or any other I/O.


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Time Sharing System

Uses time sharing to switch between multiple

jobs.

Interactive. Provides a low response time to

users.

Developed to large numbers of simultaneously

interactive users.

A program shares in time only if it exists inmemory.


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Personal System (Desktop)

Every user has his own memory, processors,

and I/O devices.

Became possible after investing micro-

processors.

Computing may be distributed to the sites

rather than central place.

Data may be shared among users throughnetworks.


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Distributed System

Computers that communicate using a network:WAN (Wide area network) orLAN (Local area

network), i.e. independent computers that works

as a single system.

Client-Server:A client is a computer that needsservice.A serveris a S/W or a H/W that do a

single service (Printing, graphics, DB, e-mail).

Peer-To-Peer: Decentralized computers provide

services to peers.

Incremental growth.


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Parallel System

A computer contains two or more CPUs that

share a common bus.

A job Should be split to discrete (independent)

small jobs.

Exponential speed up in computation needs

exponential increase in the number of

processors.


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Real-time System

Often used as a control device in a dedicated

application such as: a. Controlling scientific

experiments, b. Medical imaging systems, c.

Industrial control systems. Well-defined fixed-time constraints.

Real-time system may be eitherhard orsoft

system


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Real-time System (contd)

Hard real-time system: Secondary storage limited or absent

Data stored in short term memory.

Conflicts with time-sharing systems.

Not supported by general purpose OS.

Soft real-time system:

Useful in applications (multimedia, virtual reality).

RequireAdvanced OS features.


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Handheld Systems

Personal Digital Assistants (PDAs)

Cellular telephones

Issues:

Limited memory

Slow processors

Small display screens


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Computer Categories

Computers are generally classified in one of fourcategories: small, or microcomputers; medium-sized, ormidrange computers; large, ormainframecomputers; and super-large, or supercomputers.An emerging new category is mobile devices, as

discussed next.

In general, the larger the computer, the greater itsprocessing power. For example, big computers can

process data at faster speeds and can perform morecomplicated types of processing than can smallcomputers. Big computers can also accommodatelarger, more powerful support devices. **


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Computer Categories

Mobile devices

Microcomputers

Midrange computers

Mainframe computers

Supercomputers


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Mobile DevicesA mobile device is loosely defined as a very small

computing device based on a wireless phone orpager.

Such devices usually offerlimited Internet access in

addition to theirregular functions, such as placingphone calls and sending and receiving pages or

messages.


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Personal Computers

A technological breakthrough in the early 1970s

made it possible to produce an entire CPU on asingle silicon chip smaller than a dime. These

computers-on-a-chip, or microprocessors, can be

mass-produced at a very low cost.

Microprocessors also made it possible to build

inexpensive computer systems small enough to fit on

a desk or your lap.

The small computers at the heart of these systems

have come to be called microcomputers or

personal computers (PCs).


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Personal Computers, contd. Although most microcomputers designed for home or

business use are desktop computers, smaller PCs areavailable. Portable PCs include notebook, tablet,handheld, and pocketcomputers.

PCs designed for network use only are referred to as

network computers orthin clients.PCs or devicesdesigned for Internet access only are called Internetappliances.

Most PC users choose between two major computerplatformswhen they buy a computerPC compatiblesand Macintosh computers. Often, people refer to PC-compatible computers as the Windows platform or as IBM-compatible PCs.


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Personal Computers, contd.

PC compatiblea personal computer based

on Intel microcomputer or compatible CPUs

Macintosha type of personal computer

manufactured by Apple


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Midrange ComputersMidrange computers (orminicomputers) are regarded as

medium-sized computers. Most of them fall betweenmicrocomputers and mainframes in their processingpower.

A small or medium-sizedcompany, for example, may

find a microcomputer system

just too small or too slow to

handle its currentvolume of work.


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Mainframes Mainstay of almost all large organizations

Specialize in high-volume processing of business transactions

Mainframes often operate24 hours a day, serving dozens

of users on terminals

during regular business

hours and processing big jobssuch as payroll and billing late

at night.


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SupercomputersSome organizations, such as large scientific research

laboratories, have extraordinary demands for processingpower.

To meet applications needs such as very fast speeds andextreme degrees of accuracy, a few vendors offer verypowerful computers, called supercomputers.

Many supercomputers today

are created by linking together

multiple PCs or microprocessor

chips.


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Computer Categories vs. Systems

Mobile devices: Handheld systems.

Microcomputers: Desktop systems.

Midrange computers: Desktop & Real-timesystems.

Mainframe computers: Batch & Time-share (Hybrid

systems).

Supercomputers: Parallel & distributed systems.


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Useful Website

www.osdata.com

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