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Whatissoftware(SW)?SWis

notonlyprogramsbutalsoallassociateddocumentation,andconfigurationdata

thatmaketheseprogramsoperatecorrectly.Morespecifically,aSWsystemconsistsof

separateprogramsconfigurationfilessettinguptheseprograms

systemdocumentationdescribingthestructureofthesystemingooddetailuserdocumentationexplaininghowtouseandoperate

thesystem.

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TwoClassesofSWProducts Genericproducts These are stand-alone systems that are produced by a

development organization and sold on the open market

to any customer who is able to buy them. Examples of this type of product include software for

PCs such as databases, word processors, drawingpackages, and project-management tools.

It also includes so-called vertical applications designedfor some specific purpose such as library informationsystems, accounting systems, or systems for maintainingdental records

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TwoClassesofSWProducts Customorbespokeproducts

A software contractor develops the software especiallyfor that customer.

Examples of this type of software include controlsystems for electronic devices, systems written tosupport a particular business process, and air trafficcontrol systems.

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An important difference between these types ofsoftware is that, in generic products, the organizationthat develops the software controls the softwarespecification. For custom products, the specification isusually developed and controlled by the organizationthat is buying the software.

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WhatisSoftwareEngineering(SE)? SWengineeringisanengineeringdiscipline concerned withallaspectsofSWproductionstartingfromtheearlystageofsystemspecificationthroughtothe

maintenance ofthesystemafterit has startedtobeused. Engineering discipline

Engineers make things work. They apply theories, methods andtools where these are appropriate. However, they use them

selectively and always try to discover solutions to problems evenwhen there are no applicable theories and methods. Engineersalso recognize that they must work t organizational and financialconstraints so they look for solutions within these constraints.

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WhatisSoftwareEngineering

(SE)? All aspects of software production Software engineering is not just concernedwith the

technical processes of software development. It alsoincludes activities such as software project managementand the development of tools, methods and theories tosupport software production.

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DifferencebetweenSEand

Computer Science(CS)...? ComputerScience......isconcernedwiththeoriesandmethodswhich

establishabasisfor computersandSWsystemswhile...

SoftwareEngineering...

...isconcernedwiththepracticalproblemsofproducing

SW.

CSis asessentialforSWengineersas......physicsisfor electricalormechanicalengineers.

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Computer science theory, however, is often mostapplicable to relatively small programs. Eleganttheories of computer science cannot always be appliedto large, complex problems that require a softwaresolution.

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ThePioneeringEra(1955-1965)Newcomputerswerecomingoutalmosteveryyearor

two,renderingexistingonesobsolete.

Softwarepeoplehadtorewritealltheirprogramstorunonthesenewmachines.

Programmersdidnothavecomputersontheirdesksandhadtogotothe"machineroom".

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wererunbyJobsThePioneeringEra-2signingupformachinetimeorbyoperationalstaff.puttingpunchedcardsforinputintothemachine'scard

readerandwaiting

for

results

tocome

back

on

theprinter.

Thefieldwassonewthattheideaofmanagementbyschedulewasnon-existent.

Makingpredictionsofaproject'scompletiondatewas

almostimpossible.

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ThePioneeringEra-3Computerhardwarewasapplication-specific.Scientific

andbusinesstasksneededdifferentmachines.

Duetotheneedtofrequentlytranslateoldsoftwaretomeettheneedsofnewmachines,high-orderlanguageslikeFORTRAN,COBOL,andALGOLweredeveloped.

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ThePioneeringEra-4Hardwarevendorsgaveawaysystemssoftwareforfree

ashardwarecouldnotbesoldwithoutsoftware.Afew

companies

sold

the

service

of

building

customsoftwarebutnosoftwarecompaniesweresellingpackagedsoftware.

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ThePioneeringEra-5Thenotionofreuseflourished.Assoftwarewasfree,

userorganizationscommonlygaveitaway.GroupslikeIBM'sscientificusergroupSHAREofferedcatalogsofreusablecomponents.

Academiadidnotyetteachtheprinciplesofcomputerscience.

Modularprogramminganddataabstractionwere

alreadybeingusedinprogramming.

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The Stabilizing Era (1965-1980)Thewholejob-queuesystemhadbeen

institutionalizedandsoprogrammersnolongerrantheirjobsexceptforpeculiarapplicationslikeon-boardcomputers.Tohandlethejobs,anenormousbureaucracyhadgrownuparoundthecentralcomputercenter.

Themajorproblemasaresultofthisbureaucracy

wasturnaroundtime,thetimebetweenjobsubmissionandcompletion.Atworstitwasmeasuredindays.

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The Stabilizing Era - 2 IBM360signaledthebeginningofthestabilizingera. Largestsoftwareprojecttodateendingtheeraofafasterandcheaper

computeremergingeveryyearortwo. Softwarepeoplecouldfinallyspendtimewritingnewsoftwareinstead

ofrewritingtheold. The360alsocombinedscientificandbusinessapplicationsontoone

machine.Itofferedbothbinaryanddecimalarithmetic.Withtheadventofthe360,theorganizationalseparationbetweenscientificandbusinessapplicationpeoplecametodiminishandthishadamassiveimpactonthesociologyofthefield.Scientificprogrammerswhousuallyhadbachelordegreesfeltsuperiortobusinessprogrammers

whousuallyheldonlyassociatedegrees. Onescientificprogrammerremarked:"Idon'tmindworkingwith

businessprogrammers,butIwouldn'twantmydaughtertomarryone!"

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The Stabilizing Era - 3ThemassiveO/S,stillcominglargelyfreewiththe

computer,controlledmostoftheservicesthatarunningprogramneeded.

ThejobcontrollanguageJCLraisedawholenewclassofproblems.TheprogrammerhadtowritetheprograminawholenewlanguagetotellthecomputerandOSwhattodo.JCLwastheleastpopularfeatureofthe360.

PL/I,

introduced

by

IBM

to

mergeallprogramminglanguagesintoone,failed.Thedemandforprogrammersexceededthe

supply.

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The Stabilizing Era - 4Thenotionoftimesharing,usingterminalsat

whichjobscouldbedirectlysubmittedtoqueues

ofvariouskindswasbeginningtoemerge,meetingwithsomeresistancefromtraditionalists.

Asthesoftwarefieldstabilized,softwarebecameacorporateassetanditsvaluebecamehuge.

Stabilityleadtotheemergenceofacademiccomputingdisciplinesinthelate60's.

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The Stabilizing Era - 5Manyhigh-hypedisciplineslikeArtificial

Intelligencecameintoexistence.Asthesenewconceptscouldnotbeconvertedintopredicted

benefits,thecredibilityofthecomputingfieldbegantodiminish."StructuredProgramming"burstonthescenein

themiddleofthisera.

Standardsorganizationsbecamecontrolbattle

grounds.Thevendorwhodefinedthestandardscouldgainsignificantcompetitiveadvantagebymakingthestandardsmatchtheirowntechnology.

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The Stabilizing Era - 6

Althoughhardwarevendorstriedtoputabrakeonthesoftwareindustrybykeepingtheirpriceslow,software

vendorsemergedafewatatime.Mostcustomizedapplicationscontinuedtobedonein-

house.Programmersstillhadtogotothe"machineroom"and

didnothavecomputersontheirdesks.

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The Micro Era (1980-Present)

Thepriceofcomputinghasdroppeddramatically

makingubiquitouscomputing(i.e.,computingeverywhere)possible.Noweveryprogrammercanhaveacomputeronhisdesk.

TheoldJCLhasbeenreplacedbytheuser-friendly

GUI.

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The Micro Era - 2Thefieldstillhasitsproblems.Thesoftwarepart

ofthehardwarearchitecturethattheprogrammermustknowabout,suchastheinstructionset,has

notchangedmuchsincetheadventoftheIBMmainframeandthefirstIntelchip.Themost-usedprogramminglanguagestodayarebetween15and40yearsold.TheFourthGenerationLanguagesneverachievedthedreamof"programming

withoutprogrammers"

and

the

idea

ispretty

muchlimitedtoreportgenerationfromdatabases.There

isanincreasingclamorthoughformoreandbettersoftwareresearch.

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