Ch 1. Intro Operating System and Types

8/3/2019 Ch 1. Intro Operating System and Types

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Operating Systems

Lecture 1

BCS-III


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Prepared by: Mazhar Javed Awan 2

Computer System1. Hardware

2. Operating system

3. Applications programs

4. Users


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Computer System HardwareComputer System Hardware

Keyboard Mouse

PrinterRAM/ROM

HD

MemBus

System Bus

Monitor

CD

Processor

Floating Point

Unit

Integer

Unit

Cache

Control

Unit


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History of Computer Systems First generation 1945 - 1955

Technology: vacuum tubes, plug boards

Sign up for time, exclusive use of the machine Languages: none

OS: no operating system

Second generation 1955 - 1965 Technology: transistors, punch cards

Mainframes

Languages: FORTRAN, COBOL,

Jobs

OS: batch systems, libraries

Third generation 1965 1980 Technology: Integrated Circuits

Large mainframes and smaller machines (IBM 360 family)

Minicomputers (DEC)

OS: multiprogramming, large systems (multipart), batch and timesharing, emergenceof Unix

Fourth generation 1980 present Technology: Mass production of integrated circuits (chips and boards)

Personal computers/servers/Internet

OS: embedded -> supercomputer, CP/M -> Windows, PARC->Macintosh, Unix -> Linux/Solaris


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What is an Operating System?What is an Operating System?

Sits between programs & hardware

Sits between different programs

Sits betweens different users

But what does

it do?to provide an orderly and controlled allocation of

the processors, memories and I/O devices

among the various programs competing for them

Real Lif

e Example:Government


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Operating system interface

Hardware

OperatingSystem

Software

ComputerUser


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Operating System Goals

Accept input from input devices

Sends output from input devices

Execute user programs and make solvinguser problems easier.

Make the computer system convenient to

use. Use the computer hardware in an efficient

manner.


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Components of Operating System

Process management

Memory management

Secondary management I/O System

File System

Protection System Command interpreter system


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Operating system types

Single user

Multi user

Batch processing

Multiprogramming Time sharing

Real time system

Distributed system

Client server system Handheld

Embedded


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Single User Systems

Personal computers computer system dedicated to asingle user.

Interactive

User convenience and responsiveness.

Can adopt technology developed for larger operatingsystemsmulti-process, multi-user

Individuals usually have sole use of computer and do notneed advanced protection features.

They are popularly associated with Desk Top operatingsystem which run on standalone systems where no useraccounts are required.

Example: DOS


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Multi-User Systems:

Provides regulated access for a number of users bymaintaining a database of known users.

Refers to computer systems that support two ormore simultaneous users.

Another term formulti-useris time sharing.

Ex: All mainframes and are multi-user systems.

Example: Unix


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Batch Processing: In Batch processing same type of jobs batch (BATCH- a set of

jobs with similar needs) together and execute at a time.

First rudimentary system.

User{ operator

R

educe setup time by batching similar jobs Automatic job sequencing automatically transferscontrol from one job to another.

Resident monitor :

initial control in monitor

control transfers to job

when job completes

control transfers back to monitor


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Batch Processing (Contd):

The OS was simple, its major task was to transfer controlfrom one job to the next.

The job was submitted to the computer operator in formof punch cards. At some later time the output appeared.

The OS was always resident in memory. (Ref. Fig. )

Common Input devices were card readers and tapedrives.

Common output devices were line printers, tape drives,and card punches.

Users did not interact directly with the computer systems,but he prepared a job (comprising of the program, thedata, & some control information).

Advantage: Computer operator load data only oneoperation


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Examples

Payroll Systems

Tax systems

Production of electricity Bills National Insurance contributions


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Multiprogramming:

Multiprogramming is a technique to execute number ofprograms simultaneously by a single processor.

In Multiprogramming, number of processes reside in mainmemory at a time.

The OS picks and begins to executes one of the jobs in themain memory.

If any I/O wait happened in a process, then CPU switchesfrom that job to another job.

Hence CPU in not idle at any time.


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Multiprogramming (Contd):

OS

Job 1

Job 2

Job 3

Job 4

Job 5

Figure dipicts the layout of

multiprogramming system.

The main memory consists of 5

jobs at a time, the CP

U executesone by one.

Advantages:

Efficient memory utilization

Throughput increases

CPU is never idle, so

performance increases.


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OS Features Needed

for Multiprogramming SPOOLing (Simultaneous Peripheral

Operation On-Line)

Memory management

CPU scheduling


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Time Sharing Systems:

Time sharing, or multitasking, is alogical extension of multiprogramming.

Multiple jobs are executed by switchingthe CPU between them.

In this, the CPU time is shared bydifferent processes, so it is called asTime sharing Systems.

Time slice is defined by the OS, forsharing CPU time between processes.

Using multiprogramming to handlemultiple interactive jobs

Multiple users simultaneously accessthe system through terminals.

A job is swapped in and out of memoryto the disk if needed.

Examples Airline booking Systems

Process 1 Process 2 Process 3

OS

CPU


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Real-time Systems Well-defined fixed-time constraints. Often used as a control device in a dedicated application such as

controlling scientific experiments, medical imaging systems,industrial control systems, and some display systems.

System is automatically updated when a change is made due totransaction occur.

The terminals must be connected to the computers. Must be an online system.

Medical imaging systems

Industrial control systems

Traffic Lights

Robots

Flight Simulations


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Real-time Systems types

Hard real-timesystems: Secondary storage limited or

absent, data stored in shortterm memory, or read-onlymemory (ROM)

No virtual memorytimecannot be wasted ontranslation of logical to physicaladdresses

OS code structured for

efficiency Plane landing systems, proces

control in nuclear power plants,respirators, etc.

Soft real-timesystems Output should be produced

within the given time

constraints but if it is not,the result is not lifethreatening

Useful in applications(multimedia, virtual reality)requiring advancedoperating-system features.


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Distributed Systems

Distribute the computation amongseveral physical processors.

Loosely coupled system (clusters?)each processor has its own localmemory; processors communicate withone another through various

communications lines, such as high-speed buses , cross-bar switches,LANS, or telephone lines.

Advantages of distributed systems. Resources Sharing

Computation speed up load sharing

Reliability

Communications Disadvantages: control and OS

functions complicated, anddistributing an algorithm over thenodes is difficult.


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repared by: Mazhar Javed Awan 22

Client Server Systems

In which cooperation and intercommunication

between the various elements of a network is

conducted.

In a client server system, application programsresides in server connected to the LAN.


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P


Handheld Systems

Personal Digital Assistants (PDAs)

Cellular telephones

Issues:

Limited memory

Slow processors

Small display screens.


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P


Embedded system

Different electronic devices are controlled

Permanently store on Rom chip

Uses Mobile phone Microwave

TV sets

Examples Palm OS

Window CE

Ch 1. Intro Operating System and Types

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