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Operating System Concepts Chapter1

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    About the Presentations• The presentations cover the objectives found in the

    opening of each chapter.

    • All chapter objectives are listed in the beginning ofeach presentation.

    • You may customize the presentations to fit yourclass needs.

    • Some figures from the chapters are included. Acomplete set of images from the book can be foundon the nstructor !esources disc.

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    Chapter 1

    Introducing OperatingSystems

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    After completing this chapter, you shouldbe able to describe: Innovations in operating systems

    development The basic role of an operating system The major operating system software

    subsystem managers and their functions The types of machine hardware on whichoperating systems run

    "nderstanding #perating Systems$Si%th &dition 3

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    "nderstanding #perating Systems$Si%th &dition 4

    The di erences among batch,interactive, real-time, hybrid, andembedded operating systems

    Multiprocessing and its impact on theevolution of operating system software

    irtuali!ation and core architecturetrends in new operating systems

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    "perating systemsManage computer system hardware andsoftware

    This te#t e#plores:$hat they are%ow they wor&$hat they do

    $hy they do it This chapter describes:

    %ow operating systems wor& The evolution of operation systems

    "nderstanding #perating Systems$Si%th &dition 5

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    The "perating (ystem (oftwareach time the user sends a command, the "(

    must ma&e sure that the command ise#ecutedIf it.s not e#ecuted:

    It must arrange for the user to get a messagee#plaining the error/

    "nderstanding #perating Systems$Si%th &dition

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    The 0ser Interface The component uni1ue to each "(/0sers issue commands to the "(/

    "nderstanding #perating Systems$Si%th &dition 8

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    The four essential managers of every"(:

    Memory Manager

    2rocessor Manager3evice Manager4ile Manager

    These managers are the basis of all "(/ ach manager wor&s closely with theother managers and performs its uni1ue

    role regardless of which speci+c "( isbeing discussed/

    "nderstanding #perating Systems$Si%th &dition 9

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    "nderstanding #perating Systems$Si%th &dition 10

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    5etwor& Manager )+fth subsystemmanager*

    A networ& was not always an integral part of

    operating systemsarly systems were self-contained with all

    networ& capability added on top of e#istingoperating systems/

    5ow most "( routinely incorporate a 5etwor&Manager/Assumes responsibility for networ&ing tas&s3iscussed further in 'hapters 6 7 89

    "nderstanding #perating Systems$Si%th &dition 11

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    "nderstanding #perating Systems$Si%th &dition 12

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    egardless of the si!e or con+guration ofthe system, each of the subsystemmanagers must perform the followingtas&s:

    Monitor its resources continuouslynforce policies that determine: $ho gets what, when, and how much

    Allocate the resource )when appropriate*3eallocate the resource )when appropriate*

    "nderstanding #perating Systems$Si%th &dition 13

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    Network Manager"perating systems with networ&ing capability4ifth essential manager

    'onvenient way for users to share resourcesetains user access control

    esources include:%ardware )'20s, memory areas, printers, tapedrives, modems, and dis& drives*(oftware )compilers, application programs,and data +les*

    "nderstanding #perating Systems$Si%th &dition 14

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    In charge of main memoryandom Access Memory ) AM*

    esponsibilities include:

    2rotecting the space in main memoryoccupied by the "( itself/'hec&ing the validity of each re1uestIf it is a legal re1uest, allocates a portion ofmemory that isn.t already in use In a multiuser environment:

    setting up a table to &eep trac& of who is usingwhich section of memory

    "nderstanding #perating Systems$Si%th &dition 15

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    esponsibilities include:$hen the time comes to reclaim memory, theMemory Manager deallocates memory/

    "nderstanding #perating Systems$Si%th &dition 16

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    3etermines how to allocate the CentralProcessing Unit )'20*/

    ;eeps trac&s of the status of each process/

    An instance of program e#ecution Monitors whether the '20 is e#ecuting a

    process or waiting for a A3 or $ IT to+nish e#ecution/

    "nce the 2rocessor Manager allocates theprocessor, it sets up the necessaryregisters and tables/

    "nderstanding #perating Systems$Si%th &dition 17

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    $hen the job is +nished or the ma#imumamount of time has e#pired, The2rocessor Manager reclaims the

    processor/ The 2rocessor Manager has two levels of

    responsibility:%andle jobs as they enter the system

    %andled by

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    Monitors every device, channel, and controlunit/

    esponsibilities include:

    'hoosing the most e=cient way to allocate all ofthe system.s devices:2rinters, ports, dis& drives, etc/>ased on a scheduling policy chosen by the system.sdesigners/

    Accomplished by:Allocating the device(tarting device operation3eallocating the device ma&ing it available to thene#t process or job/

    "nderstanding #perating Systems$Si%th &dition 19

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    ;eeps trac& every +le in the systemincluding:

    3ata +les, program +les, compilers, andapplication programs

    esponsibilities include:nforcing user?program restrictions on who has

    access to which +les by using predeterminedaccess policies/

    'ontrolling what user?programs are allowed todo with +les once they access them/ The 4ile Manager allocates the necessaryresources and later deallocates them )>y closingthem*/

    "nderstanding #perating Systems$Si%th &dition 20

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    The +fth essential manager for those "(with Internet or networ&ing capability/

    2rovides a convenient way for users toshare resources while controlling users.access to them/

    These resources include:%ardware such as: (oftware such as:

    '20s 'ompilersMemory areas Application program2rinters 3ata +les

    Tape drivesModems3is& drives

    "nderstanding #perating Systems$Si%th &dition 21

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    The portion of the "( that users interactwith directly/

    2reviously, the user interface consisted of

    commands typed on a &eyboard anddisplayed on a monitor/ 5ow most systems allow users to choose

    a menu option from a list/

    "nderstanding #perating Systems$Si%th &dition 22

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    ach individual manager must perform itsindividual tas&s and must be able to wor&harmoniously with every other manager/

    e1uires incredible precision 5o single manager performs tas&s in

    isolation/

    "nderstanding #perating Systems$Si%th &dition 23

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    4or e#ample @ someone chooses a menuoption to e#ecute a program/ Thefollowing steps must occur in se1uence:

    The 3evice Manager must receive theelectrical impulses from the mouse or&eyboard, form the command, and send thecommand to the 0ser interface/

    The 2rocessor Manager validates thecommand and sends an ac&nowledgement tobe displayed on the monitor so the userreali!es the command has been sent/

    "nderstanding #perating Systems$Si%th &dition 24

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    $hen the 2rocessor Manager receives thecommand, it determines whether the program mustbe retrieved from storage or is already in memory,and the noti+es the appropriate manager/If the program is in storage, the 4ile Manager mustcalculate its e#act location on the dis& and pass thisinformation to the 3evice Manager, which retrievesthe program and send it to the Memory Manager/

    The Memory then +nds space for it and records itse#act location in memory/ "nce the program is in

    memory, the Memory Manager must trac& itslocation in memory )even if it.s moved* as well asits progress as it.s e#ecuted by the 2rocessorManager/

    "nderstanding #perating Systems$Si%th &dition 25

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    $hen the program has +nished e#ecuting, itmust send a +nished message to the 2rocessorManager so that the processor can be assignedto the ne#t program waiting in line/

    4inally, the 2rocessor Manager must forward the+nished message to the 3evice Manager, so thatit can notify the user and refresh the screen/

    Though oversimpli+ed, this demonstration

    illustrates some of the incredible precisionre1uired for the "( to wor& smoothly/

    "nderstanding #perating Systems$Si%th &dition 26

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    To appreciate the role of the "()software*, we need to discuss theessential aspects of the computer

    system.s hardware:Main memory (RAM)

    $here data and instructions must reside to beprocessed/

    Input/Output de ices (I/O de ices)Includes every peripheral unit in the system:2rinters, dis& drives, '3?3 3 drives, ashmemory, &eyboards, etc/

    "nderstanding #perating Systems$Si%th &dition 27

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    To appreciate the role of the "()software*, we need to discuss theessential aspects of the computer

    system.s hardware:Central processing unit (CPU)

    The brains with the circuitry )chip* to control theinterpretation and e#ecution of instructions/

    'ontrols the operation of the entire computersystem/All storage references, data manipulations, andI?" operations are initiated or performed by the'20/

    "nderstanding #perating Systems$Si%th &dition 28

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    Computer classi!cation0ntil the mid-86B9s, computers wereclassi+ed by capacity and price/

    Main"rameA large machine in si!e and in internalmemory capacity/

    The I>M CD9, introduced in 86DE, is a classice#ample of an early mainframe/

    The I>M CD9 Model C9 re1uired 8F-s1uare-footair-conditioned room to house the '20, theoperator.s console, a printer , a card reader, anda &eypunch machine

    "nderstanding #perating Systems$Si%th &dition 30

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    Main"rame# The '20 was G feet high and D feet wide%ad an internal memory of DE; )large for itsday*

    A price tag of H 99,999 in 86DE dollars/>ecause of its si!e and price at the time, itsapplications were generally limited to largecomputer centers/

    Minicomputer#3eveloped to meet the needs of smallerinstitutions/"ne of the early minicomputers was mar&etedby 3igital 1uipment 'orporation/

    The 232-F was less than H8F,999/"nderstanding #perating Systems$

    Si%th &dition 31

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    Minicomputer#3eveloped to meet the needs of smallerinstitutions/"ne of the early minicomputers was mar&etedby 3igital 1uipment 'orporation/

    The 232-F was less than H8F,999/(maller in si!e and memory capacity/'heaper than mainframes/

    Today, computers that fall betweenmicrocomputers and mainframes are oftencalled midrange computers/

    "nderstanding #perating Systems$Si%th &dition 32

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    $upercomputer#3eveloped for primarily for governmentapplications needing massive and fastnumber-crunching ability to carry out militaryoperations and weather forecasting/>usiness and industry became interested inthe technology when the massive computersbecame faster and less e#pensive/A 'ray supercomputer is a typical e#amplewith D to thousands of processors performingup to /E trillion oating-point operations persecond )tera ops*/

    "nderstanding #perating Systems$Si%th &dition 33

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    $upercomputer#"ften used to perform the intricatecalculations re1uired to create animatedmotion pictures/%elp oil companies in their search for oil byanaly!ing massive amounts of data/

    "nderstanding #perating Systems$Si%th &dition 34

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    Microcomputer3eveloped to o er ine#pensive computationcapability to individual users in the late 86B9s/

    arly models featured a revolutionary amount

    of memory @ DE;/ Their physical si!e was smaller than theminicomputers of that time, though larger thanthe microcomputers of today/

    ventually, microcomputers grew to

    accommodate software with larger capacity andgreater speed/ The distinguishing characteristic of the +rstmicrocomputer was its single-user status/

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    %orkstations2owerful microcomputers developed for useby commercial, educational, andgovernment enterprises/

    Typically networ&ed together and are used tosupport engineering and technical users whoperform:

    Massive mathematical computations

    'omputer-aided design )'A3*"ther applications re1uiring powerful '20s,large amounts of main memory, and e#tremelyhigh-resolution graphic displays/

    "nderstanding #perating Systems$Si%th &dition 36

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    $er ers2owerful computers that provide speciali!edservices to other computers or client?server

    networ&s/#amples can include:2rint serversInternet servers

    -Mail serversach performs critical networ& tas&s/

    "nderstanding #perating Systems$Si%th &dition 37

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    Ad ances in computer tec&nology(ince the mid-86B9s, rapid advances incomputer technology have blurred the

    distinguishing characteristics of earlymachines/ 2hysical si!e, cost, and memory capacity

    The most powerful mainframes today havemultiple processors coordinated by the2rocessor Manager/(imple mainframes still have a large mainmemory, but now they.re available in des&-si!ed cabinets/

    "nderstanding #perating Systems$Si%th &dition 38

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    Ad ances in computer tec&nology5etwor&ing is an integral part of moderncomputer systems because it can connectwor&stations, servers, and peripheral devicesinto integrated computing systems/5etwor&ing capability has become a standardfeature in many computing devices:

    2ersonal organi!ers, personal digital assistants

    )23As*, cell phones, and handheld $eb browsers/At one time, computers were classi+ed bymemory capacity now they.re distinguishedby procesor capacity classi+cation/

    "nderstanding #perating Systems$Si%th &dition 39

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    Ad ances in computer tec&nologyMoore.s Jaw

    In 86DG, Intel e#ecutive Kordon Moore observed

    that each new processor chip contained roughlytwice as much capacity as its predecessor, andeach chip was released within 8F- E months ofthe previous chip/%e predicted that the trend would causecomputing power to rise e#ponentially overrelatively brief periods of time )Moore.s Jaw*/

    "nderstanding #perating Systems$Si%th &dition 40

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    "perating systems for large and smallcomputers fall into +ve categoriesdistinguished by:

    esponse timer%ow data is entered into the systems/

    'i e Categories#>atch (ystems

    Interactive (ystemseal-Time (ystems%ybrid (ystems

    mbedded (ystems

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    atc& $ystems#3ate from the earliest computers

    elied on stac&s of punched cards or reels ofmagnetic tape for input

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    Interacti e $ystemsKives a faster turnaround than batch systems/(lower than real-time systems/Introduced to satisfy the demands of users whoneeded fast turnaround when debugging programs/

    e1uired the development of time-sharing software:Allows each user to interact directly with the computersystem via commands entered from a typewriter-li&eterminal/

    The "( provides immediate feedbac& to the user andresponse time can be measured in fractions of asecond/

    "nderstanding #perating Systems$Si%th &dition 43

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    Real time $ystems#0sed in time-critical environments wherereliability is &ey and data must be processed

    within a strict time limit/(ystem response time must meet thedeadline or ris& signi+cant conse1uences/(ystems also need to provide contingencies

    to fail gracefullyMust preserve as much of the system.scapabilities and data as possible to facilitaterecovery/

    "nderstanding #perating Systems$Si%th &dition 44

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    Real time $ystems# Two types of real-time systems, depending onthe conse1uences of missing the deadline:

    %ard eal-time (ystems:is& total system failure if the predicted time

    deadline is missed/(oft eal-Time (ystems:

    (u er performance degradation, but not totalsystem failure, as a conse1uence of a misseddeadline/

    "nderstanding #perating Systems$Si%th &dition 45

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    Real time $ystems#Although it.s theoretically possible to converta general-purpose "( into a real-time system

    by merely establishing a deadline, theunpredictability of these systems can.tprovide the guaranteed response time thatreal-time performance re1uires/

    Most embedded systems and real-timesystem environments re1uire "(s that arespecially designed to meet real-time needs/

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    *y+rid systemsA combination of batch and interactivesystems/

    Appear to be interactive because individualusers can access the system and get fastresponses/Accepts and run batch programs in thebac&ground when the interactive load is light/

    Ta&es advantage of the free time betweenhigh-demand usage of the system and low-demand times/Many large computer systems are hybrids/

    "nderstanding #perating Systems$Si%th &dition 48

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    ,m+edded systems'omputers placed inside other products toadd features and capabilities:

    %ousehold appliancesAutomobilesngine performance, bra&ing, and navigation

    3igital music playerslevators

    2acema&ers

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    ,m+edded systems3esigned to perform a speci+c set of programs5ot interchangeable among systems

    >efore a general-purpose "( such as Jinu#,05I , or $indows can be used in an embeddedsystem:

    The system designers must select whichcomponents from the entire "( are needed in thatparticular environment/

    The +nal version of the "( will include only thenecessary elements/Any unneeded features or functions will bedropped/

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    -. 0s# !rst generation (-. 0 1 -.22)A time of vacuum tube technology andcomputers the si!e of classrooms/

    ach computer was uni1ue in structure andpurpose/Jittle need for standard os software becauseeach computer.s use was restricted to a fewwor&ing professionals wor&ing on mathematical,

    scienti+c, or military applications/A typical program would include everyinstruction needed by the computer to performthe tas&s re1uested/

    "nderstanding #perating Systems$Si%th &dition 51

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    -. 0s# !rst generationA typical program would include everyinstruction needed by the computer to

    perform the tas&s re1uested/It would give e#plicit directions to the cardreader

    $hen to begin, how to interpret the data on thecards, when to end

    The '20%ow and where to store the instructions inmemory, what to calculate, where to +nd the data,where to send the output/

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    -. 0s# !rst generationA typical program would include every instructionneeded by the computer to perform the tas&sre1uested/

    The output device$hen to begin, how to print out the +nished product, how toformat the page, when to end/

    The machines were operated by the programmersfrom the main console/

    To debug a program, the programmer would:(top the processor

    ead the contents of each register, ma&e the correctionsin memory locations/

    esume operations/

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    -. 0s# !rst generation To run programs, the programmers wouldhave to:

    eserve the machine for the length of time theyestimated it would ta&e to e#ecute theprograms/

    As a result the machine was poorly utili!ed/ The '20 processed data and made calculationsfor only a fraction of the available time/

    The entire system sat idle betweenreservations/

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    -. 0s# !rst generationIn time:

    'omputer hardware and software became morestandard

    The e#ecution of a program re1uired fewersteps and less &nowledge of the internalwor&ings of the computer/'ompilers and assemblers were developed totranslate into binary code the nglish-li&ecommands of the evolving high-levellanguages/

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    -. 0s# !rst generationudimentary operating systems started to

    ta&e shape with the creation of:MacrosJibrary programs(tandard subroutines0tility programs3evice driver subroutines

    2rewritten programs that standardi!ed the wayinput and output devices were used/

    "nderstanding #perating Systems$Si%th &dition 56

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    -. 0s# !rst generation These early programs were at a signi+cantdisadvantage

    They were designed to use their resourcesconservatively at the e#pense ofunderstandability/Many programs used convoluted logic only theoriginal programmer could understandIt was nearly impossible for anyone else todebug or change a program later on/

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    -.20s# second generation (-.22 1 -.32)3eveloped to meet the needs of new mar&ets

    Kovernment>usiness researchers

    The business environment placed much moreimportance on the cost e ectiveness of the system/'omputers were still very e#pensive )H 99,999*

    Throughput had to be ma#imi!ed to ma&e such an

    investment worthwhile for business use The usage of the system had to be drasticallyincreased/

    "nderstanding #perating Systems$Si%th &dition 59

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    -.20s# second generation (-.22 1-.32)

    Two widely adopted improvements:

    'omputer operators were hired to facilitateeach machine.s operation

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    -.20s# second generation (-.22 1-.32)

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    -.20s# second generation (cont4d5)>ut, even with batching techni1ues, thefaster second-generation computers allowede#pensive time lags between the '20 andthe I?" devices/

    A job with 8D99 cards could ta&e B6 seconds tobe read by the card reader and only G secondsof '20 time to assemble or compile/

    The '20 was idle 6EL of the time and busyonly DL of the time it was dedicated to that job/

    This resulted in poor overall system use/

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    -.20s# second generation (cont4d5)ventually, several factors helped improve

    '20 performance:I?" devices speed gradually became faster

    Tape drives, dis&s, and drums To use more of the available storage area in theI?" devices, records were grouped into bloc&sbefore they were retrieved or stored/

    >loc&ing(everal logical records are grouped within one

    physical record/

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    -.20s# second generation (cont4d5)Access methods developed

    Added to object code by lin&age editor To reduce the speed discrepancy between the I?"and the '20, an interface (control unit) wasplaced between them to act as a bu er /

    An interim storage area that wor&s as a temporaryholding place/As the slow input device reads one record, the

    control unit places each character of the record intothe bu er/$hen the bu er is full, the entire record is 1uic&lytransmitted to the '20/

    "nderstanding #perating Systems$Si%th &dition 65

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    -.20s# second generation (cont4d5) The process is just the opposite for outputdevices:

    The '20 places the entire record into thebu er, which is then passed on by the controlunit at the slower rate re1uired by the outputdevice/

    An early form of spooling was developed bymoving oNine the operations of card reading,printing, and OpunchingP/

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    -.20s# second generation (cont4d5) Techni1ues were developed to:

    Manage program libraries'reate and maintain each data dire t accessaddress'reate and chec& +le labels/

    Timer interrupts were developed to:Allow job sharing

    2revent in+nite loops on programs that weremista&enly instructed to e#ecute a single seriesof commands forever/

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    -.30s# t&ird generation3esigned with faster '20s(peed sill caused problems with slower I?"devicesMultiprogramming

    Introduced the concept of loading manyprograms at one time and sharing the attentionof a single '20/

    Allowed each program to be serviced in turn,one after anotherIntroduced the concept of the interrupt

    The '20 was noti+ed of events needing operatingsystem services

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    -.30s# t&ird generationIntroduced the concept of the interrupt )contid*

    The '20 was noti+ed of events needing operatingsystem services

    $hen a program issued a print command, itgenerated an interrupt re1uesting the services ofthe I?" processor and the '20 was released tobegin e#ecution of the ne#t job/2assive Multiprogramming @ The "( didn.tcontrol the interrupts but waited for each job toend an e#ecution se1uence/If a job was '20-bound, it could tie up the '20for a long time while other jobs had to wait/

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    -.30s# t&ird generationIntroduced the concept of the interrupt )contid*

    To resolve this problem, the "( was given a moreactive role with the advent of active

    multiprogramming/Allowed each program to use only a preset sliceof '20 time/$hen time e#pired, the job was interrupted andanother job was allowed to begin e#ecution/

    The interrupted job had to wait until it wasallowed to resume e#ecution later/ The idea of time-slicing soon became common inmany time-sharing systems/

    "nderstanding #perating Systems$Si%th &dition 70

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    -.30s# t&ird generation2rogram scheduling

    Initiated with second-generation systems'ontinues today'omplicated by the fact that main memory wasoccupied by many jobs2roblem resolved by sorting jobs into groupsand then were loaded into memory according toa preset rotation formula/

    "ften determined by priority or memoryre1uirements/

    "nderstanding #perating Systems$Si%th &dition 71

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    -.30s# t&ird generationIn addition to scheduling jobs, handlinginterrupts, and allocating memory, the "(also had to resolve con icts whenever two

    jobs re1uired the same device at the sametime/4ew major advances were made in datamanagement/

    "nderstanding #perating Systems$Si%th &dition 72

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    -.60sven faster '20s

    The +rst 'ray supercomputer was released in86BD/(peed continued to cause problems with slowerI?" devicesMultiprogramming schemes to increase '20use were limited by the physical capacity of themain memory which was a limited resource andwas very e#pensive/

    The solution was virtual memory Too& advantage of the fact that the '20 couldprocess only one instruction at a time/

    "nderstanding #perating Systems$Si%th &dition 73

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    -.60s$ith virtual memory, the entire programdidn.t need to reside in memory beforee#ecution could begin/

    The program would be divided into parts andwould be &ept in secondary storage, bringingeach part into memory only as it was needed/2rogrammers of second-generation

    computers had used this concept with the rollin?roll out programming method )overlays* toe#ecute programs that e#ceeded the physicalmemory of those computers/

    "nderstanding #perating Systems$Si%th &dition 74

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    -.60sAt this time there was also growing attentionto the need for data resource conservation/3atabase management software became apopular tool

    It organi!ed data in an integrated manner,minimi!ed redundancy, and simpli+ed updatingand access of data/

    A number of 1uery systems were introducedthat allowed even the novice user to retrievespeci+c pieces of the database/

    "nderstanding #perating Systems$Si%th &dition 76

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    -.60s These 1ueries were made via a terminal whichmandated a growth in terminal support anddata communication software/2rogrammers soon became more removedfrom the intricacies of the computer/Application programs started using nglish-li&ewords, modular structures, and standardoperations/

    This trend toward the use of standardsimproved program management becauseprogram maintenance became faster andfaster/

    "nderstanding #perating Systems$Si%th &dition 77

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    -.70s3evelopment in the 86F9s dramatically improvedthe Cost/per"ormance ratio of computercomponents%ardware was more e#ible hardware with logicalfunctions built on easily replaceable circuit boards>ecause it was less costly to create these circuitboards, more "( functions were made part of the

    hardware itself )+rmware*A program is permanently held in read-only memory) "M* as opposed to being held in secondarystorage

    "nderstanding #perating Systems$Si%th &dition 78

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    -.70s The job of the programmer changeddramatically

    >ecause many programming functions were being

    carried out by the system.s software, theprogrammer.s tas& is much simpler and lesshardware dependent/

    The industry moved to multiprocessing%aving more than one processor

    More comple# languages were designed tocoordinate the activities of the multipleprocessors servicing a single job

    Allowed parallel program e#ecution"nderstanding #perating Systems$

    Si%th &dition 79

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    -.70s The evolution of personal computers andhigh-speed communications spar&ed themove too networ&ed systems and distributed

    processingnabled users in remote locations to share

    hardware and software resources These systems re1uired a new &ind of "( @

    one capable of managing multiple sets ofsubsystem managers, as well as hardwarethat might reside half a world away/

    "nderstanding #perating Systems$Si%th &dition 80

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    -.70s$ith network operating systems , usersgenerally

    >ecame aware of the e#istence of many

    networ&ed resources'ould log in to remote locations'ould manipulate +les on networ&ed computersdistributed over a wide geographical area

    5"( were similar to single-processor "( inthat each machine ran its own local "( andhad its own users/

    "nderstanding #perating Systems$Si%th &dition 81

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    -.70s The di erence was in the addition of a networ&interface controller with low-level software todrive the local "(, as well as programs to allowremote login and remote +le access/$ith distri+uted operating systems , userscould thin& they were wor&ing with a typicaluniprocessor system when, in fact, they wereconnected to a cluster of many processors

    wor&ing closely together/0sers didn.t need to &now which processor wasrunning their applications or which devices werestoring their +les/

    "nderstanding #perating Systems$Si%th &dition 82

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    -.70s These details were all handled transparentlyby the "(/

    The disadvantage of such a comple# "( wasthe re1uirement for more comple# processor-scheduling algorithms/'ommunications delays within the networ&sometimes meant that scheduling algorithms

    had to operate with incomplete or outdatedinformation/

    "nderstanding #perating Systems$Si%th &dition 83

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    -..0s The demand for Internet capability in themid-8669s spar&ed the proliferation ofnetwor&ing capability/

    The $$$, conceived in a paper, by Tim>erners-Jee made the Internet accessible bycomputer users worldwide, not just theresearchers who had come to depend on itfor global communications/$eb accessibility and e-mail becamestandard features of almost every "(/

    "nderstanding #perating Systems$Si%th &dition 84

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    -..0s$eb accessibility and e-mail becamestandard features of almost every "(/

    Increased networ&ing, however, also spar&edIncreased demand for tighter security toprotect hardware and software

    The decade also produced a proliferation ofmultimedia applications demandingadditional power, e#ibility, and devicecompatibility for most "(/

    "nderstanding #perating Systems$Si%th &dition 85

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    -..0sA typical multimedia computer housesdevices to perform audio, video, and graphiccreation and editing/

    These functions can re1uire speciali!eddevices such as:

    Microphone3igital pianoMusical Instrument 3igital Interface )MI3I*3igital camera3igital video disc drive )3 3*

    "nderstanding #perating Systems$Si%th &dition 86

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    -..0s"ptical disc drives )'3*(pea&ers

    Additional monitors2rojection devices'olor printers%igh-speed Internet connections

    These computers also re1uire speciali!edhardware )controllers, cards, busses* andsoftware to ma&e them wor& properly/

    "nderstanding #perating Systems$Si%th &dition 87

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    -..0sMultimedia applications need large amountsof storage capability that must be managed

    gracefully by the "(/

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    8000s The new century emphasi!ed the need for "ss too er improved e#ibility, reliability, and speed/

    To meet this need, the concept of virtual machineswas developed and became commercially viable/9irtuali:ation#

    The creation of partitions on a single server, witheach partition supporting a di erent "(/

    It turns a single physical server into multiple virtual

    servers, often with multiple "sse1uires the "( to have an intermediate manager to

    oversee each "(s access to the server.s physicalresources/

    "nderstanding #perating Systems$Si%th &dition 90

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    8000s9irtuali:ation#

    $ith virtuali!ation, a single processor can run DEindependent "(s on wor&stations using aprocessor capable of allowing DE separate threads)instruction se1uences* to run at the same time/

    Processing $peed%as enjoyed similar advancement with thedevelopment of multi-core processors/A single chip can hold multiple processor cores/A dual-core chip allows two sets of calculationsto run at the same time/

    "nderstanding #perating Systems$Si%th &dition 91

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    8000sProcessing $peed

    The "( must now manage the wor& of these

    multiple processors and be able to scheduleand manage the processing of their multipletas&s/

    "nderstanding #perating Systems$Si%th &dition 92

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    ;&reads#Multiple actions that can be e#ecuted at thesame time/

    The 2rocessor Manager is responsible forprocessing each job submitted by user/

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    ;&reads#A process has two characteristics:

    It passes through several states )running, waiting,ready* from its initial arrival into the computersystem to its completion/

    Multiprogramming and virtual memory dictate thatprocesses be swapped between main memory andsecondary storage during their e#ecution/$ith conventional processes )heavyweightprocesses*, this swapping results in a lot ofoverhead/

    ach time a swap ta&es place, all process informationmust be saved to preserve the process.s integrity/

    "nderstanding #perating Systems$Si%th &dition 94

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    ;&reads#A thread )lightweight process* is a unit smallerthan a process, which can be scheduled ande#ecuted/

    0sing this techni1ue, the heavyweight process,which owns the resources, becomes a morepassive element, while a thread becomes theelement that uses the '20 and is scheduled fore#ecution/

    (ome "( support multiple processes with a singlethread, while others support multiple processeswith multiple threads/Multithreading allows applications to manage aseparate process with several threads of control/

    "nderstanding #perating Systems$Si%th &dition 95

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    ;&reads#$eb browsers use multithreading routinely/"ne thread can retrieve images whileanother sends and receives e-mail/

    "nderstanding #perating Systems$Si%th &dition 96

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    The +rst "(s were designed as acomprehensive single unit/

    They stored all re1uired elements of the "( inmemory

    Memory allocation2rocess scheduling3evice Allocation4ile management

    'umbersome and time consuming forprogrammers to add new components to the"( or to modify e#isting ones/

    "nderstanding #perating Systems$Si%th &dition 98

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    5ow, the part of the "( that resides in memoryhas been limited to a few essential functions

    2rocess schedulingMemory allocation

    All other functions are provided by specialmodules which are treated as regularapplications

    3evice Allocationasier to add new components or modify

    e#isting ones/"bject-oriented design was the driving forcebehind this new organi!ation/

    "nderstanding #perating Systems$Si%th &dition 99

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    "bjects are self-contained modules thatprovide models of the real world and can bereused in di erent applications/2rogrammers can modify and customi!epieces of an "( without disrupting theintegrity of the remainder of the system/0sing a modular, object-oriented approachcan ma&e software development groups modeproductive than was possible with procedural

    structured programming/

    "nderstanding #perating Systems$Si%th &dition 100

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    "perating system overview 4unctions of "(

    Manages computer system%ardware and software

    4our essential managers$or& closely with the other managers andperform uni1ue role

    5etwor& Manager

    "perating systems with networ&ing capabilityssential hardware componentsMemory chips, I?", storage devices, and '20

    "nderstanding #perating Systems$Si%th &dition 102

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    volution of "(sun increasingly comple# computersun increasingly comple# computer systems

    2rior to mid-86B9s'omputers classi+ed by capacity and price

    3ramatic changes over timeMoore.s Jaw: computing power rises e#ponentially2hysical si!e, cost, and memory capacity

    Mobile society information delivery'reates strong mar&et for handheld devicesIntegral in modern computer systems

    "nderstanding #perating Systems$Si%th &dition 103

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    4ive categories of operating systems>atch, interactive, real-time, hybrid, andembedded

    0se of object-oriented design improves thesystem architecture

    (everal ways to perform "( tas&s 3esigner determines policies to match

    system.s environment 5e#t:

    #plore details of operating system components