Encyclopedia of Computer Science and Technology

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Python 393Perl is still a popular scripting language for UNIX andWeb-related applications. Perl contains a powerful builtinregular expression and pattern-matching mechanism, aswell as many other built-in functions likely to be useful forpractical scripting. Python, on the other hand, is a moregeneralized and more cleanly structured language that islikely to be suited for a wider variety of applications, andit is more readily extensible to larger and more complexapplications.Further ReadingLutz, Mark. Learning Python. 3rd. ed. Sebastapol, Calif.: O’Reilly,2007.———. Programming Python. 3rd ed. Sebastapol, Calif.: O’Reilly,2006.Python Programming Language—Official Web site. Available online.URL: http://www.python.org/. Accessed August 17, 2007.Zelle, John M. Python Programming: An Introduction to ComputerScience. Wilsonville, Ore.: Franklin, Beedle & Associates,2004.
Qquality assurance, softwareModern software programs are large and complex, and containmany interrelated modules. If a program is not thoroughlytested before it goes into service, it may containerrors that can result in serious consequences (see risks ofcomputing).In the early days of computing, programmers generallytested their code informally and nonsystematically. Theassumption was that after the program was given to the usersany problems that arose could be fixed through “patches”or replacement versions containing bug fixes. Today, however,it is increasingly recognized that assuring the qualityand reliability of software requires a systematic, comprehensiveprocess that begins when software requirements are firstspecified and continues after the program has been released.Any program is designed to meet the needs of a specifictype of users for specific applications. Therefore, thefirst step must be to make sure that users are able to communicatetheir requirements and that the software engineersunderstand the users’ needs and concerns. Detailedwritten specifications, flowcharts, and other depictions ofthe program can be reviewed by user representatives (seeflowchart and case). The specifications can be furtherexplored by creating a prototype or demonstration of theprogram’s features (see presentation software). Since aprototype can be dynamic and let users have simulatedinteractions with the program, it may reveal usability problemsthat would be hard to spot from charts or documentation.The result of this initial verification process shouldbe that the users agree that the program will do what theyneed and that they will be comfortable using it.In moving from design to implementation (writing theactual code), the developers must first choose an appropriateapproach (see algorithm) and data representation.Choosing an algorithm that is known to be sound is preferable,but if an algorithm must be modified (or a new onedeveloped), developers may be able to take advantage ofmathematical techniques that will suggest, if not totallyprove, the algorithm’s accuracy and reliability.As the programmers write the code, they should try touse best practices (see software engineering). Doing soensures that the code will be readable and organized insuch a way that the source of a problem area can be identifiedeasily, and any “fix” that must be made will be lesslikely to have unforeseen side effects.Developers can also include special code that will facilitatetesting. This code can include assertions—statements that testspecified conditions (such as variable values) at key points inthe program, displaying appropriate messages if the valuesare not within the proper range. Large, complex programscan also include diagnostic modules that give the developers asort of virtual console that they can use to monitor conditionswhile the program is running, or “drill into” particular areasfor closer inspection (see bugs and debugging).Although a certain amount of testing and debugging canand should be done while the code is being written, moreextensive and systematic testing is usually performed aftera preliminary version of the program has been completed.(This is sometimes called an alpha version.) There are twobasic approaches to designing the tests. “White box” tests usethe developer’s knowledge of the code to design test data thatwill test all of the program’s structural features (see proce-394
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Encyclopedia ofComputer scienceand
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C on t e n t sAcknowledgmentsivintr
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I n t r od u c t ion to t h eR e v
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Introduction to the Revised Edition
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AdaAdaStarting in the 1960s, the U.
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Advanced Micro Devices (AMD)Image P
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Algolgrammar of the data-descriptio
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ALUdown into component parts or bui
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10 Amdahl, Gene MyronShanahan, Fran
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12 analog and digitalhistory, bring
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14 Andreessen, MarcCompleted in 193
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16 animation, computerAndreessen tr
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18 APLAPL (a programming language)T
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20 application program interfacerat
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22 application softwareURL: http://
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24 arrayIn languages such as C that
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26 artificial intelligenceby tradit
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28 artificial lifewriters such as V
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30 Atanasoff, John VincentAtanasoff
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32 authoring systemsway”—the se
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34 awkthose found in C. There are a
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36 backup and archive systemsthe ec
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38 Backus-Naur formBackus-Naur form
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40 basic input/output systemdecisio
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42 Bell Laboratoriesand the early a
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44 Bezos, Jeffrey P.use if it is to
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46 bioinformaticsand a hierarchy of
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48 biometricsvariety of biometric s
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50 bitmapped imagesuch tasks as gra
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52 blogs and bloggingThe shift oper
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54 boot sequenceoperators (called B
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oadbandTechnically, broadband refer
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Brooks, Rodney 59such as Flickr and
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ulletin board systems 61bugs and de
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66 CTotal = Total + 1;Total += 1;To
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68 C++While attracted to the advant
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70 calculatorthe location of the ca
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72 cascading style sheetsMojave Des
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74 CD-ROM and DVD-ROM“rapid proto
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76 censorship and the InternetIn 20
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78 central processing unitcentral p
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80 CGIIn a newly emerging sector th
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82 characters and stringsAs compute
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84 chess and computersOne of the be
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86 chipsetattached to the silicon s
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90 clock speedSinclair, Joseph T.,
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92 codecMurcah, Mike, Anne Prince,
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94 COMcommon object request broker
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96 compilersuch as a keyword (reser
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98 computer-aided design and manufa
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100 computer crime and securitycomp
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102 computer forensicsa device proc
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104 computer graphicsthe same time,
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106 computer industryso on). By cre
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108 computer industrypackages serve
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110 computer virus• What is the b
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112 computer visionsense on the par
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114 conferencing systemsFeldman, Mi
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116 cookiesunlike most traditional
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118 CORBA“activation” or “val
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120 CraigslistMano, M. Morris, and
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122 CRMtasks can be assigned to dif
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124 cyberneticsMany issues regardin
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126 cyberstalking and harassmentThe
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DdataToday the term data is associa
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130 database administrationsignal m
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132 database management systemMicro
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134 data compressionlocal network,
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136 data securityparticular purpose
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138 data typeswhile a list has one
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140 Dell, Inc.User Interface—The
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142 design patternsdesign patternsD
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144 device driverOne Laptop per Chi
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146 digital cashcould be worked bac
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148 digital dashboardThe ownership
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150 Dijkstra, Edsger W.discs. A big
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152 disaster planning and recoveryT
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154 distributed computingAnother wa
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156 DNSCSCUCVCXCYCZDEDJDKDMDODZECEE
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158 documentation of program codewi
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160 document modelSociety for Techn
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162 DRMresearchers. For example, Al
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164 DVRMPEG file) that is fully com
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166 e-books and digital librariesha
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168 e-commerceRemington Rand. Worki
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170 education and computersApplicat
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172 e-governmentlenges face educati
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174 Electronic Artsteaching softwar
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176 e-maillanguages. However this c
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178 employment in the computer fiel
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180 encapsulationconsist of a combi
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182 Engelbart, DouglasEngelbart, Do
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184 entrepreneurs in computinganaly
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186 error correctionSalvendy, Gavri
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188 expert systemsAnatomy of an Exp
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190 Feigenbaum, Edwardhttp://hissa.
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192 file serverdata integrity. Vers
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194 film industry and computingImpl
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196 firewallcontrolled by a state t
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198 flash and smart mobs(or even pr
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200 flowchartused to hold data. The
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202 FORTRANearly days of microcompu
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204 fuzzy logicdefining and arrangi
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206 Gates, William, IIIGame console
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208 Geographical Information System
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210 Google• downward wage pressur
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212 government funding of computer
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214 graphics formatsof objects so t
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216 grid computingoff. By 2000, vir
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218 Grove, Andrew S.Cavalancia, Nic
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220 handwriting recognitionand othe
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222 hard disk• remote surgery, wh
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224 health, personalTo search a has
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226 history of computingFurther Rea
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228 history of computingThe most st
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230 home officeFacing vigorous comp
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232 HTML, DHTML, and XHTMLFurther R
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234 hypertext and hypermediaImpleme
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236 IBM PCFurther ReadingBashe, Cha
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238 identity theftfrom meetings to
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240 information retrievalinvasion o
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242 information warfareShannon foun
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244 installation of softwareinstall
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246 internationalization and locali
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248 Internettransmission of a messa
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250 Internet censorshipDunaev, Serg
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252 interpreterconsidered to be ISP
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JJavaJava is a computer language si
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256 JavaScriptIn 2006 Sun Microsyst
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258 Jobs, Steven Paulan enthusiasti
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260 journalism and the computer ind
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262 Joy, Billwho will be unable to
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264 kernelcould send a message to t
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266 knowledge representationattende
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268 Kurzweil, RayFurther ReadingFre
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LLAN See local area network.languag
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272 laptop computerapplications for
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274 Lessig, Lawrencepleadings and o
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276 library, programadditional copi
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278 linguistics and computingIn his
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280 LISPA Linux system running Open
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282 list processinga rich variety o
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284 Logoa checksum, and two special
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286 LuaNext CharValHere Char$ is a
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288 macroMacDailyNews. Available on
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290 mainframeMaes has participated
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292 map information and navigation
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294 mashupsbefore you buy” softwa
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296 Mauchly, John WilliamMoving fro
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298 measurement units used in compu
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300 medical applications of compute
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302 memory managementTom’s Hardwa
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304 microprocessorMicroprocessor de
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306 Microsoft .NETbrowser had broug
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308 Microsoft WindowsIntroduced in
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310 middlewareBott, Ed, Carl Sieche
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312 minicomputer“How Military Rob
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314 Mitnick, Kevin D.———. “
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316 molecular computingdevice could
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318 Moore, Gordon E.only one gun, w
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320 Motorola CorporationMotorola Co
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322 multimediaa maximum of 640 kB o
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324 multitasking“local” memory
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326 music and video distribution, o
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328 music and video players, digita
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330 natural language processingplac
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332 Net Neutrality• Do not post b
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334 networkGoogle Groups, is the be
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336 neural networkwebmd.com/stroke/
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338 numeric dataselect customer whe
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340 object-oriented programmingPARC
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Page 373 and 374: 360 parallel porthis work. Papert l
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Page 395 and 396: 382 printersarray of magnetically c
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Page 403 and 404: 390 PrologGiven the scope and pace
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Page 419 and 420: 406 RFIDParts of an RFID system. De
Page 421 and 422: 408 risks of computingHafner, Katie
Page 423 and 424: 410 roboticsMac. The MIT computer s
Page 425 and 426: 412 RPGHenderson, Harry. Modern Rob
Page 427 and 428: 414 Rubya file, as with many script
Page 429 and 430: 416 satellite Internet serviceFurth
Page 431 and 432: 418 science fiction and computingre
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Page 447 and 448: 434 smart buildings and homesThis m
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Page 453 and 454: 440 social networkingThere continue
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444 software piracy and counterfeit
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446 sorting and searching• Discma
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448 sound file formatsapproach, and
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450 Spafford, Eugene H.and computer
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452 spreadsheetSpeech recognition b
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454 SQLFurther Reading“Antispywar
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456 stackstackOften a temporary sto
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458 Stoll, CliffordCharles Babbage
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460 structured programmingsuited fo
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462 supply chain managementApplicat
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464 system administratorsystem admi
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Ttablet PCAs the name suggests, a t
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468 TclHaylor, Phil. Computer Stora
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470 technical supportIPv6 Informati
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472 technology policyDuring the 198
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474 telepresence• elimination of
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476 text editortyping commands into
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478 touchscreencode. This would mea
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480 trends and emerging technologie
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482 Turkle, SherryFurther ReadingHe
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Uubiquitous computingTraditionally
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486 USB% who | awk ' { print $1 }'H
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488 user groupsGarofoli, Joe. “Us
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VvariableVirtually all computer pro
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492 videoconferencingconsequence wa
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494 virtualizationused as an expres
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496 VoIPtank crews and even individ
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498 von Neumann, JohnJohn von Neuma
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WWales, Jimmy(1966- )AmericanIntern
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502 Web 2.0 and beyond“Web 2.0”
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504 webcamabout a 75 percent market
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506 Web page design• fluency in t
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508 Web servicesWhen a user types i
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510 Wiener, Norbertcomplexity . . .
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512 wikis and WikipediaWiki softwar
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514 Wirth, NiklausMobile Wireless N
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516 word processingto promote netwo
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518 World Wide WebBy the beginning
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XXMLSeveral markup languages have b
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YY2K problemSherlock Holmes once re
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524 YouTube• excessive time spent
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526 Zuse, Konradneeded would make t
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528 Appendix IRed Herring: The Busi
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530 Appendix IIing company (CTR) in
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532 Appendix II• Users of the new
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534 Appendix II••ibm developed
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536 Appendix II• Bill Gates and P
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538 Appendix II• A consortium cal
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540 Appendix II• Apple released o
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Appendix IIISome Significant Awards
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544 Appendix III1993 Juris Harmanis
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546 Appendix III1972 Paul E. Dirkse
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548 Appendix IIIJohn W. BackusRober
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550 Appendix IIIsity of Manchester
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552 Appendix IIIthereby enhancing A
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554 Appendix IVInternational Webmas
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556 IndexAnalytical Engine 35-36, 3
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558 Indexdata communications over13
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560 Indexgraphics in 106, 194haptic
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562 IndexDertouzos, Michael L. 141D
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564 IndexFFacebook 16, 440-441, 487
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566 IndexIDNA (Internationalizing D
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568 Indexin open-source movement352
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570 IndexMinard, Joseph 239mind 92-
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572 IndexOnStar 71ontologies and da
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574 Indexin object-orientedprogramm
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576 Indexsequential calculator 5ser
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578 Indexterminals in 475-476user i
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580 Indexdatabases in 132developmen
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