PRESENTATION ON OPERATING SYSTEM

OPERATING SYSTEMITS TYPES: TIMESHARING PARALLELDISTRIBUTED&PC OPERATING SYSTEMS

CONTENTSWHY TIMESHARING ?EVOLUTIONMEANINGWORKINGRR SCHEDULINGCOMPLEXITYADAVNTAGES AND DISADVANTAGES

Why were timesharing OS developed?

Less human-computer interactionSingle user was inefficientBecause early mainframes and minicomputers were extremely expensive

The concept was first described publicly in early 1957 by Bob Bemer. The first project to implement a time-sharing system was initiated by John McCarthy in late 1957

The first commercially successful time-sharing system was the Dartmouth Time-Sharing System (DTSS) which was first implemented at Dartmouth College in 1964

Evolution of timesharing OS

Thomas Kurtz (left) and John Kemeney

Meaning of time sharing: “sharing of a computing resource among many users by means of multiprogramming and multitasking”

The meaning

◦Multiprogramming:

◦ more than one processor in close communication, sharing computer bus , clock and memory and peripherals sometimes

◦ Multitasking:◦ method by which

multiple tasks, share common processing resource such as CPU. The CPU executes multiple tasks by switching b/w them so frequently that users may interact each program while it is running.

Working of time sharing sys. The user gives instructions to the OS or to a program

directly using mouse or keyboard and waits for immediate results

Uses CPU scheduling to select a job Programs queued for execution in FIFO order. Like multiprogramming, but timer device interrupts after a

quantum (time slice).◦ Interrupted program is returned to end of FIFO◦ Next program is taken from head of FIFO

OS assigns some time slots to each job. Here,  each job is executed according to the allotted time slots.

               Job1: 0 to 5               Job2: 5 to 10               Job3: 10 to 15

Implementing RR scheduling algorithm.

Considerations influencing choice of time quantum◦ Shouldn’t be so large◦ Shouldn’t be so small

Time quantum= 4 milliseconds

P1 P2 P3 P1 P1 P1 P1 P1

0 4 7 10 14 18 22 26 30

Complexity … Timesharing systems are more complex

then multiprogrammed OS that needs :◦ Memory management and protection◦ Virtual memory: process needs to be swapped in

and out of memory to disk in order to obtain a reasonable time

◦ File systems: online file system is required for users to access data and code

◦ Disk management: as file system resides on collection of disks

◦ Sophisticated CPU scheduling schemes

A time-sharing system (what we call a server nowdays) provides many many people the opportunity to use the system. Technically, even a standard PC is a time-sharing system, because you can run many different programs on it at a time (think Browser, iTunes, Anti-Virus, etc.). The old mainframe systems had a card reader and an output. Only one set of cards could be run through at a time. So, if payroll was running through all 14000 employee's paycheck calculations, you had to wait until they were done. Modern mainframe systems have some time-sharing capabilities by allowing multiple processes to run on the system, but those processes are virtualized, rather than a true sharing system. However, the details of that can be left to others. There are benefits and downsides to every type of system. In a mainframe-style system, all resources are available to the process being run, which benefits large data crunching operations (like payroll). The downside to a mainframe-style system is that only one process can run at a time in each virtual machine.

In a server-style system, all resources are shared among all processes. If a process "runs away" by using more processes than it should, then the other processes suffer, which the end-user sees as a server responding very slowly and/or "timing out". The upside to a server-style system is that you can serve web pages to thousands of people, while at the same time handling thousands of pieces of email.

If you go for a little bit of luxury and the convenience for your vacation, then, timeshares might be the one you're looking for. But if you're on a tight budget, this may not be for you especially with our crisis-stricken economy. The number one disadvantage of this is the cost involve like the maintenance fees.

in short

Time sharing…

Advantages are :◦ CPU efficiency. ◦ each user gets CPU time.

Disadvantage :◦ complex OS required.◦ since all output devices are centralized on a

single PC therefore there will be time delay from one person to another.

Parallel operating systems

Contents:Its meaningworkingTypesApplication and scope

Also known as multiprocessor systems

More than one processor, sharing –computer buses, clock, memory and peripherals.

Parallel operating systems

CPU CPUCPU

MEMORY

How it works?

Principle behind it ◦ Large problems can often be divided into smaller

ones, which are then solved concurrently◦ A parallel system works by dividing the set of

calculations into smaller parts and distributing them b/w the machines on a network

How do the communication takes place?◦ Shared memory◦ Distributed memory

Why were they introduced?

Using a single processor become limiting factor in applications like:◦ weather forecasting, simulation, image

processing, statistical data analysis How the problem was tackled?

◦ Dividing it into modules◦ Combining with network based service resulting in

distributed computing

Types of multiprocessingAsymmetric multiprocessing

◦ Each processor is assigned a specific task;◦ Master processor schedules and allocated work to slave

processors◦ More common in extremely large systems

Symmetric multiprocessing (SMP)◦ Each processor runs and identical copy of the operating

system◦ Many processes can run at once without performance

deterioration◦ Most modern operating systems support SMP

Advantages Increased throughput: as there are no. of

processors are increased Economy of sale: save money as they can

share peripherals, mass storage and power supplies

Increased reliability: failure of one processor will not halt the entire system but only slows it

graceful degradation fail-soft systems

PARAM 8000

Intel ASCI Option Red Supercomputer

Distributed operating systems

Distribute computation among many processors.

Loosely coupled -no shared memory, various communication lines ,each processor has its own local memory; processors communicate with one another through various communications lines, such as high speed buses or telephone linesclient/server architectures

A Distributed System

resources

server

client

network

SITE A SITE B

SITE C

communication

Loosely coupled Multiprocessing configuration

Advantages Resources Computation speed up – load

sharing Reliability Communications Sharing

Establishing distributed systems Requires networking infrastructure Local area networks (LAN) or Wide area

networks (WAN) May be either client-server or peer-to-

peer systems

General structure of client server

client

server

client client client

network

Advantages and applications

Benefits: Apps:

◦ resource sharing ◦ computation speed-

up◦ reliability◦ communication -e.g.

email

◦ digital libraries, digital multimedia

Personal computing operating systems

• Single user systems, portable.• I/O devices -keyboards, mice,

display screens, small printers.• Laptops and palmtops, Smart

cards, Wireless devices.• Single user systems may not

need advanced CPU utilization or protection features.

• Advantages: user convenience, responsiveness, ubiquitous

Contents Older Operating System

◦ MS-DOS◦ Microsoft Windows like:-◦ Window NT◦ Window 95◦ Window 98 Common Operating System◦ Window XP◦ Window ME◦ Window CE◦ Linux

Operating systems widely used in PC’s The operating system of a computer performs

basic tasks such as: recognizing information from the keyboard and mouse, sending information to the monitor, storing of information to the hard drive, and controlling device peripherals as printers and flatbed scanners.  

Operating systems provide the basis for running common applications such as word processors and Internet browsers. Operating systems are also responsible for running Assistive Technology applications such as screen magnifiers, and applications that read text aloud. 

MS-DOS

Window NT

Window 95

Window 98

Older operating systems

Ms- Dos

Command-line interface

Prompt – system is waiting for you to do something

Single user single-tasking OS

Command line interface

16-bit OS, powerful, fast

Strong security Versions

◦ NT Workstation◦ NT Server

Drawbacks◦ Lacks support for older Windows and MS-DOS

software and hardware◦ Complex to learn and use◦ Requires more memory and processing power

Windows NT (new technology)

Windows 95 and 98

Self-contained OSDOS commands still availableStart programs by

Start buttonDouble clicking the icon

Long file names up to 255 characters

XP means eXperience-Desktop computer

2 versions Professional Client Personal Client

New and updated features Start Menu and Taskbar improvements Faster start-up, Fast user switching

Windows XP

Multimedia support -- Windows Media Player 7 Jukebox

◦ Record music CDs as digital files Windows Movie Maker

◦ Basic video editing Windows Image Acquisition

◦ Scanner and digital camera Reliability Features

◦ System File Protection◦ Auto Update◦ System Restore

Windows ME millennium edition

Where used Embedded systems

◦ Industrial controllers◦ Robots◦ Office equipment◦ Cameras◦ Telephones◦ Home entertainment devices

Pocket PC Internet appliance market

Subset of Windows Less memory

Smaller screens

Little or no file storage

Provides Internet connectivity

Windows CE (Consumer Electronics)

LINUX-like OS Open-source software

◦ Download it free◦ Make changes◦ Restriction – any changes must be freely available to the public

PC Setup◦ PC comes with Windows installed◦ Install LINUX in a dual-boot configuration

Advantages over Windows◦ Extremely stable◦ Internet support◦ Reinstallation is simpler

Disadvantage◦ Scarcity of applications

Linux

Operating system Features Examples

Timesharing Simultaneous user interaction, on-line file systems

Multics file system (1965), Unix (1974)

Parallel Hierarchical systems, extensible kernels, parallel programming concepts, secure parallel languages

RC 4000 system (1969), 13 Venus system (1972),14 Boss 2 system (1975),

Personal computing Graphic user interface OS 6 (1972),Pilot system (1980)

Distributed Remote servers VFS file server (1979),Unix united RPC (1982),Amoeba system (1992)

Summary ….

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