; TeX output 1998.01.13:1225n@P\2ٓRcmr7Lite$ra teProgramminginCsBY6XQ cmr12Thre/߆T cmtt12CWEBSys[tEemofStructureSdSoftwareDoScu9mentationrK`y cmr10ManUualUUfor4'ExXformÎatemployeGdbyCWEBʨ, whichcanb#eus1eGdtroa ecttUhe app#eqaranceofCWEBtdoGcurments.Section9i#sdTevotUeGdtroacompar*i#sonwitUhLevy/KnurthCWEBh;g nÎallys1ectionUU10surmmÎar*i#seGsallCWEB1codTesrecogni#s1edintUhesourcetUext.*n썫2|{Ycmr8ABOUTXLITERAJTEPRÎOGRAMMINGCWEBxMANUALn@P2A\rbQoutTlit"e Drafteprogramming?卫LitUe rate=programminrgi#saconcepttUhatwasdTevelop#eGd,AimplementUed,Aand=propagatUed=byD.E.KnUurth=intUhe eqarly 1980's,asanÎaturals1equeltrotUheconceptof\structureGdprogramminrg"tUhathadcaus1eGdarevolurtionintUheworldofsoftwaredTevelopmentabGourtadTecadeeqarlie r.S(AttUhi#smoment, anotUhe rdTecadefurtUhe r, onemÎayconcludTeFtUhatlitUe rateFprogramminrghasnotcaus1eGdas#imilarrevolurtion,Is#incemÎanyprogramme rspracticinrgillitUe rateWprogramminrgdonotfeelatallasguilrtyabGourttUhi#sastheywouldiftUheywe retrob#efoundpracticinrgurnstructureGdUUprogramming.)qSoletus rstUUcons#idTe rtUheideqaofstructureGdUUprogramminrgmoreclos1ely*.5F C cmbxti10Structuri>edprogramming WitUhÎourt attUemptingadTe nitionoftUhetUe rm,(8its1eemsf#airtrosaytUhatstruc-tureGdP+programminrginvolveGsdTes#igninrgaprogrambyhie rarchicaldTecompGoqs#itionoftUhetaskathand,andconstructinrgaprogramtUhathasas#imilardTecompGoqsitionintroparts,whe reeqachpart\solveGs"tUhecorreGspond-inrgFJsuUbtask.DThesuUbGdivi#sionoftUheprogrammÎanifeGstsits1elfinitsdivi#sionintrosuUbroutineGs(procedures,furnctions),andattUhemoredTetaileGdlevelintUhesyntacticcompGoqs#itionoftUhÎoqs1erourtineGs(controlstructureGs,bloGcks);tUhi#s1explainswhymUuchemphas#isisplaceGdontUheus1eofsubrourtineGs,handwhylanrguageGswitUhalineqaruprogrammoGdTeland(conditionÎal)jurmpqsastUheGirmÎaincontrolstructure(likeasqs1em|qblylanrguage)donotUformanÎaturalvehicleforstructureGdprogramminrg.sThequeGstionastrowhichcr*itUe riaUshÎouldb#eus1eGdinsuUbGdividinrg}problemsintosmÎalle roneGsi#sdiculttoanswe ringene ral,FburtagoGod}ruleoftUhum|qb}i#stUhatattUhes%levelofabqstractionatwhichataski#sdTe neGditshÎouldb#epoqss#ibletrogiveareasonÎablys#impleinformÎaldTeGsTcr*iptionofitssuUbtasks,inwhichanewlevelofdTetailabGourttUhemetUhÎoGdus1edtrop#e rformtUhetaski#sgiven.(It)wouldb#eniceiftUhesuUbtasksalsohads#impleformÎalspeci cations,]burtingene raltUhi#sistroGomUuch)toask, s#inceRinformÎaldTeGsTcr*iptionsdonotonlyabqstractf*romimplementationdTetails, tUheymÎayalsoconceqalnUurme rousUUobvioussp#eci cationdTetails). 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ConcludinrgZwemÎaysaytUhatstructureGdprogramminrginitstraditionÎalformdo#eGsnotencourageorevenallowtUhelevelofdoGcurmentationtUhatwouldb#edTeGsirableformÎaintUenanceandintUelligibilitybyp#eopleotUhe rtUhanUUtheUUaurthÎoroftheprogram.wRi>equirements forliteri>ateprogramming The3bas#icidTeqaoflitUe rate3programminrgistrotake3afunda-mentallydi e rentstartinrgpGointfortUhepreGs1entationofprogramstrohUumÎanreqadTe rs,!witUhourtanydirecte ectontUheprogramass1eenbytUhecompurtUe r.̘RatUhertUhantropreGs1enttUheprogramintUheforminwhichitwillb#ecompileGd(orexecurtUed),aandtrointUe rcalatecommentstrohelphUurmÎansundTe rstandwhati#sgoinrgon(andwhichs?tUhecompile rwillkindlyignore),tUhepreGs1entationfoGcus1esonexplaininrgtohUumÎanstUhedTeGs#ignandconstructionoftUheprogram,whilepieceGsofactualprogramcoGdTeareins1e rtUedtromÎaketUhedTeGsTcr*iptionpreci#s1eandUtrotUelltUhecompurtUe rwhatitshÎoulddo.sTheprogramdTeGsTcr*iptionshÎoulddTeGsTcr*ib#epartsoftUhealgor*itUhmastUheyoGccurinthedTeGs#ignprocesqs,ratUhe rthaninthecompletUeGdprogramtext.:F*orreqasonsofmÎaintainabilityiti#seGsqs1entialhÎoweve rtUhattUheprogramdTeGsTcr*iptiondTe neGstUheactualprogramtUext;iftUhi#swe redTe neGdinas1eparatUesourcedoGcurment,)tUhenincons#istencieGswouldb#ealmoqstimpoqss#ibletroprevent.n Ifprogramsarewr*ittUen'inawaytUhatconcentratUeGsonexplaininrgtUheirdTes#igntrohUumÎanreqadTe rs,0tUhentheycanb#econsidTe reGdasworksof(tUechnical)litUe rature;iti#sfortUhisreqasontUhatKnurthhasnÎameGdtUhi#sstyleofsoftwareconstructionand dTeGsTcr*iption\litUe rateprogramminrg".Morebackground informÎationabGourttUhi#sconceptanditshi#stroryconceptcanb#efourndinKnUuthsbGook\LitUe rateProgramminrg",CSLI׼LecturenoteGs#27,LelandStanfordJurniorUUUnive rs#ity*,1992(ISBN0-937073-81-4). F*rom|tUhedi#sTcusqsion|abGoveitwillb#ecleqartUhattraditionÎalprogramminrglanguageGsarenotdirectUlysuitablefor'litUe rateprogramminrg..W*eshallnowtrytroformUulatUerequirementsforasystUemtUhatsuppGortslitUe rateprogramminrg.Doing =soweshalleGsp#eciallykeepinmindprogramstUhatevolveaftUe rtUheGiror*iginÎaldTes#ign,pGoqss#iblyalrtUe r*ingce rtainpartsoftUhatdTeGs#ign,aandpGoqss#iblybeGinrgreqalis1eGdbydi e rentpe rsons,asinceitisinsuchUUcas1eGstUhattheb#ene tsoflitUe rateUUprogramminrgareparticularlycrucial. The/doGcurmentationpartsoftUheprogramdTeGsTcr*iptionshÎouldallowfortUhesamef*reeGdomofexpresqs#iontUhatonedwouldhaveinanordinÎarytUechnicalpap#e r.F!ThismeqanstUhattUhedoGcurmentdTeGsTcr*ibinrgtUheprogramshÎouldcons#istofformÎattUeGdtext,ratUhe rthanb#eGinrgaplaintUext le.`ThisdoeGsnotexcludTetUhepoqss#ibilitytUhattUhesourceMi#swr*ittUenasaplaintext le,burttUhenitshÎouldundTe rgosomeformofproGcesqs#inrgMtoproGducetUheactual %programdTeGsTcr*iption.XbThedoGcurmentshÎouldmoreove rcontainf*ragmentsofaprogramwr*ittUeninsometraditionÎal(structureGd)programminrglanguage,insuchawaytUhattUheycanb#emechanicallyextractUeGdandarranrgeGdlintoacompletUeprogram;intUheformÎatteGddocurmentontUheotUhe rhandlayourtandchÎoiceoffontsforUUtUheGs1eprogramf*ragmentsshÎouldb#esoastromaximi#s1ereqadrability*. 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ThisnÎameisfolloweGdby` !", cmsy10'andtUheprogramcoGdTetUhatconstiturtUeGstUhemoGduleits1elf;,tUhi#siscalleGduadTe ninrgoccurrenceoftUhemodulenÎame.&(W*emÎakeadi#stinctionb#etweentUhewords`s1ection'and`moGdule',$4us#inrgtUheforme rforanUurm|qb#ereGdportionoftUheWEBdoGcurment,$4andtUhelattUe rforanÎameGdportionof^UtUheprogramdTeGsTcr*ib#ed^Ubyit.)A^RmoGdulenÎamecanalsob#eus1eGdintUhebGody^UofsomeotUhe rmoGdule,`eitUhe rb#efore%oraftUe ritsdTe nitionintUhedoGcurment,to%repreGs1enttUhecorreGspondinrg%pieceofprogramtUext.6WEBf#acilitatUeGsaflocatinrgaftUhedTe nitionofamoGdulef*romtUheplacewhe reiti#sus1eGdbyaurtomÎaticallyincorpGoratinrgtUheLnurm|qb#e rofthedTe ninrgs1ectionintUhemoGdulenÎame.WTheactualprogramtUexti#stUhenconstructUeGdbyrecurs#ively{replacinrgmoGdulenÎameGsbytUhetUextsp#eci eGdintUheGirdTe nition(tUhi#sshÎouldofcours1efollowtUhegrammÎaticalstructureoftUheprogram, BleGsttUhemoqstbas#icpr*incipleGsoflitUe rateprogramminrgb#eviolateGd).Alprogramlf*ragmentoGccurrinrgattUheoutUe rmoqstleveli#sdistinrguisheGdlbytUhef#acttUhatiti#snotheqadTeGdbyamoGduleUUnÎame. MoqstmoGdulenÎameGswillhavejustonedTe ninrgoGccurrence,~andwillalsob#erefe renceGdjustonce;SinbotUhcas1eGs3tUhe remÎayhoweve r3b#eexceptions,&where3amoGdulenÎamehasmoretUhanoneoGccurrenceoftUheindicatUeGdkind.xIfWamoGdulei#smUulrtiplyrefe renceGd,X,tUhi#ssimplymeqanstUhattUhecorreGspondinrgWpartoftUheprogramtUexti#srepeqatUeGdidTenticallyinmoretUhanoneplace.NIfamoGdulenÎamehasmoretUhanonedTe ninrgoGccurrence,tUhentUhetUextofthecorreGspondinrgmodulei#sobtaineGdbyconcatUenÎatinrgtUheprogramf*ragmentsofallitsdTe nitionsintUheordTe rinwhichtUheyoGccurintUhedoGcurment.kInas#imilarfashionallf*ragmentswitUhÎourtmoGdulenÎamearecom|qbineGdintroan\unnÎameGdmodule".KXThes1earetUheonlyoccas#ionswhe retUheordTe rinwhichtUhes1ectionsare!givencanhaveanye ectontUhe nÎalprogram;oapartf*romtUhi#sthelitUe rate!programme rhascompletUef*reeGdomUUofordTe rinrgtUhes1ectionsinawaytUhatf#acilitatUeGsurndTe rstandinrgUUtUheprogramasmUuchaspGoqss#ible. W*e! neeGdnotdi#sTcusqsallaspectsofWEB(systUemshe re,TburtafewpGointstUhatcontr*iburtUetolitUe rate! pro-gramminrg]byimprovinrgreqadability]shÎouldb#ementioneGd.The]prope r]formÎattinrgofallprogramf*ragmentsi#saurtomÎaticallytakencareofbytUheWEBF systUem,@providinrgauniformstyleofpreGs1entation.SThesystUemalsomprovidTeGsalargeamourntofcroqss-refe renceminformÎation;ytUhi#sgreqatlyf#acilitatUeGsreqadinrgtheprogramands1eqarchinrgtforsp#eci cpieceGsofcodTe.%Notonlyi#stUhenurm|qb#e rofthe( rst)ts1ectiondTe ninrgamoGduleincor-pGoratUedUinitsnÎame,#burtintUhatdTe ninrgs1ectionindicationsarealsogivenoftUhes1ection(s)inwhichtUhemoGdulei#sus1ed,andpoqss#iblyofanyfurtUhe rdTe ninrgoGccurrencesoftUhesamemoGdulenÎame.AttUheendoftUhe,?doGcurmentanalphab#eticallysortUeGdindTexi#saddeGd,4wli#stinrgforeqachidTenti e ralltUhes1ectionsinwhichiti#sdTe neGd$orus1ed;tUheprogramme rmÎayalsoaddadditionÎalentr*ieGstrotUheindTexbyindicatinrgintUheprogramsource=tUhatce rtains1ectionsshÎouldb#erefe renceGdforparticulartUe rms.+AA=li#stofallmoGdulenÎameGsi#salsogiven,XwhichWmÎayhelploGcatinrgtUhepartoftUheprogramdTeqalinrgwitUhsomei#sqsue.xQSoinmÎanywaystUheWEBsystUemtr*ieGstroaidhUumÎanundTe rstandinrgoftUheprogram,burtofcours1etUhelitUe racyoftUheprogramme rwillalwaysUUremÎaintUhedTeci#siveUUfactrorintUhisreGspect.3Wh9aftTaCWEBprogramloQokslikeEnough4nowofgene ralcons#idTerations,lletustur#nourattUentiontrotUheCWEBsystUemtUhi#smÎanuali#sreqallyabGourt.Theb#estwaytroleqar#nabGourtiti#sprobablytroreqadaCWEBdoGcument.The reforeweincludTeasmÎall|burtcompletUeCWEBprogramb#elow;tUhe|programisabGourtassmÎallaspoqss#ible|witUhÎourtrendTe r*ingadTecompGoqs#ition/intromodulespointUlesqs.eTheexamplei#snotintUendTeGdasashÎowpieceofprogramminrglitUe racy*,burtMZitdTemonstratUeGsvqar*iousasp#ectsoftUhesystUem.oTheindTexattUheendoftUheprogrami#sincludTeGd,NburtnottUhe/li#stofthefourmoGdulenÎameGsintUhi#sprogramorthetableofcontUents.[One/willnoticetUhatsomesym|qbGolsapp#eqartrobedi e rentf*romtUheGirocialrepres1entationinC ,forinstancetUheasqs#ignmentop#e ratror`=e'app#eqarsasi`(',tUheequalityop#e ratror`== b'as`=',tUhelogical\and"and\or"op#e ratrors`&& b'and`|| b'as`^'and`_'reGsp#ectively*,?tUhe9vqar*iable`f1 b'as` b> cmmi10fٓRcmr71|s',?andtUhenUullpGointUe r`NULL\'as` ';thusthepGoqss#ibilities9oftUhetyp#eGs1ettinrgsystUemUUareus1eGdtroimproveUUtUheapp#eqaranceoftUheprogram.n썫6WHAJTXACWEBPRÎOGRAMLOOKSLIKECWEBxrMANUALn@P1. Compar1ing<_t"ext leQs.Thi#sSisanentirelytr*ivialprogram,tUhattUeGstswhetUhe rtwotUext leGsareequal, andUUifnotso,pGointsourttUhe rstUUpGointofdi e rence.{#include 6 #include 6 t9yp(eQdef4Wlc9harMobQooJlcI;2. ThewdourtUlineoftUheprogrami#ssimple.W*ereqadcharactUe rsf*rombGotUhinpurt lesintroc1׫andc2urntiltUhecompar*i#sonUUiscompletUe.qLineandcolurmncountsaremÎaintaineGdin$': cmti10lineandc}'ol.#de n9e 6leftىffmar}'ginAO31=leftmoqstUUcolurmnnUum|qb#e r;changeUUto0ifyouprefe r= hF*urnctions@5i in tmain *(intɱn;c9har#(ar}'g6{)  fFILE1I6Jf1|s; f2;=tUheUUtwoinpurt leGs=in t%˱c1|s;c2;c}'ol޷(leftىffmar}'gin4;long,line@M(1;{hOp#en`tUhe leGsf1.andf2|s,ctakinrgtUheGirnÎameGsf*romtUhecommÎandlineorf*romtUhetUe rminÎal;fnincas1eof(anUUe rrorforwhichnorecove ryi#spGoqssible,UUcallexitk(1)@6ihSeqarchUUfor rstUUdi e rence,leavinrgc1C6=c2ȫifandonlyifadi e rencewasfournd@3ihRepGortUUtUheourtcomeoftUhecompar*i#son@4iret9ur(n7٫0;=succeGsqsfulUUcompletion= g3. TheheqartoftUheprogrami#stUhissimpleloGop.MJWhenwereqachtUheendofoneoftUhe leGs,tUhe leGsmÎatchifandHlonlyiftUheotUhe r lehasalsoreqacheGditsend.myF*ortUhi#sreqasonthetUeGstc1C=c2|s,KwhichrequireGscharactUe rstrob#ereqadf*rombGotUh les,mUustprecedTetUhetUestfor leend;whenonlyone leends,iti#stUheforme rtUeGstwhichUUbreqakstUheloGop.{hSeqarchUUfor rstUUdi e rence,leavinrgc1C6=c2ȫifandonlyifadi e rencewasfournd@3i while芫((c1C(getc(f1|s))=(c2(getc(f2|s))8^c16=EOFh)if(c1C='\n'h)f++G line"b|;c}'ol(leftىffmar}'gin4;gels9?e5++Uc}'ol'; {Thi9sXco_"r"hOp#enhwtUhe leGsf1andf2|s,m@takinrgtUheGirnÎameGsf*romtUhecommÎandlineorf*romtUhetUe rminÎal;rincas1eofan e rrorUUforwhichnorecove ryi#spGoqssible,UUcallexitk(1)@6i O!cmsy7n;++G ar}'g ;=ignoreUU\argurment"0,whichi#stUheprogramnÎame= if(n=0)fop}'enadffrv le+k(&f1|s;"First file to compare"h; );op}'enadffrv le(&f2|s;"Second file to compare"h; );g els9?eif(n=1) ff1C(stdinDX;if((f2C(fop}'enK(ar}'g;r}'eadffmode0%ѫ))= )fprintf 6("Could not open file %s.\n"h;ar}'gz);exita(1);g g els9?eif(n=2) fop}'enadffrv le:k(&f1|s;"Give another first file"h;ar}'g++!ë);op}'enadffrv le:k(&f2|s;"Give another second file"h;ar}'gz); g els9?e5fprintf 6("No more than two command line arguments are allowed.\n"h);exita(1);g Thi9sXco@Par}'g: 2 fe,6. bQooJl+[: 1 fe,c5.buf: 7 fe.c}'ol Lɫ: 2 fe,y3,4.c1|s: 2 fe,3,4.c2|s: 2 fe,3,4.EOFF_: 3,4.exita: 6.f: 7 fe.ush : 7.fop}'enG3: 6,r7.f1|s: 2 fe,3,6.f2|s: 2 fe,3,6.getc2Ы: 3.isff rst: 5 fe.leftffmar}'gin0%: 2 fe,03.line\: 2 fe,m3,4.>@Pmain "): 2 fe. ऱn: 2 fe.name : 7 fe.op}'enff le: 6,Uj7Ujfe Uk.printfګ: 4,#U5,6,7.pr}'ompt=: 7 fe.r}'eadffmode"SD: 6 fe,;7.sc}'anf |X: 7.stdin ]: 6.stdoutȫ: 7.theff le: 4,l!5l!fe l".0n썫8WHAJTXACWEBPRÎOGRAMLOOKSLIKECWEBxrMANUALn@PSome*ari>emarksabouttheexampleprogram ReqadinrgZotUheprogramshÎouldnotcaus1egreatproblemstro anyone6f#amiliarwitUhtheC lanrguage,'ExX'smÎatUh moGdTe),producinrgtUhesameformÎattUeGdourtʪputwitUhÎoutus#ingtUhef#acilitieGsofCWEB&h.QBurteventUheniti#sprefe rableOtrous1eCWEB%instUeqad,Pb#ecauseitwilltUhenguarantUeethatallidTenti e rsmentioneGdinsuchawayintUhe=doGcurmentationpartofas1ectionorinacomment,willb#eincludTeGdintUheindTexattUheendoftUheprogram.AlrtUhÎoughinmanycas1eGsarefe rencewouldhaveb#eengene ratUeGdanywaybytUheprogramf*ragmentintUhesames1ectionS(ashapp#ensinallcas1eGsforourexampleprogram),StUhismechanismSensureGstUhatevenremÎarksabGourttUhe8us1eofvqar*iableGsandfurnctionsmÎadTeins1ectionstUhatcontainnoprogramf*ragmentatallcanb#etraceGdf*romz(tUheindTex.?Incidentally*,\identi e rsz(tUhatareus1eGdonlyinamodulenÎamearenotindTexeGd,\whichi#swhytUhe reUUi#snoreferencetrox2intUheindTexentryforexitk. WhenanindTexentryi#srecordeGd,whetUhe rf*romwithinaprogramf*ragmentorapieceofC coGdTeem|qb#eddTedin)tUext,tUheoGccurrencemÎayb#e aggedas`dTe ninrg',dep#ending)ontUhecontUext;8thi#shappens)forinstanceintUhecas1eofparametUe rsinanANSI/ISO1stylefurnctionheqadinrg,:ofvqar*iabledTeclarationsandoflab#els. IfatleqastoneXoGccurrenceofanidTenti e rinsomes1ectioni#sadTe ninrgone,tUhentUhecorreGspondinrgXs1ectionnUurm|qb#e rintheindTexxentryfortUhatidTenti e rwillb#eurndTe rlineGd.(GSingle-lettUe rxidTenti ers,tUhexsp#ecialidTenti e rNULLx(app#eqar*inrgas)` '),^andkeywordsoftUhelanrguagearecons#idTe reGdsouUbiquitoustUhatnoindTexrefe renceGsfortUhemaregene ratUeGd, exceptQtUhÎoqs1ethatareurndTe rlineGd;Se.g., intUheexampletUhe rei#snoreferencetroxj6fortUhevqar*iablen.F*orϪkeywordstUhi#smeqanstUhattUheywillnotapp#eqarintUheindTexatall(urnleGsqstUheprogramme rexplicitUlymÎarksce rtain oGccurrencesasdTe ninrg);)#notUehÎoweve rtUhatidTenti e rsdTe neGdinat9yp(eQdef-(*dTeclaration(likebQooJlQointUheUUexample)willb#eindTexeGd,eventUhÎoughtheyares1etinbGoldf#acejustlikekeywordsare.FurtherЃattributesofCWEBmpri>ograms Anasp#ectofCWEBprogramstUhatdoeGsnotstandourtve rycleqarlyin ourminiatureexamplei#stUhatitallowss1etsofrelatUeGdsectionstrob#egroupeGdtrogetUhe rinto\chaptUe rs".EachZchaptUe ri#sidTenti eGdbyitstitUle,[whichapp#eqarsinbGoldfaceaftUe rtUhenurm|qb#e rofits rsts1ection;#\inourǬexamples1ections1and8startnewchaptUe rs.Thedivi#sionǬintrochaptUe rshasafewmoree ectsontUhedoGcurment,?whichwe resuppreGsqs1edinourexample,?s#incetUheywouldintUe rferewitUhtheove rallstructureoftUhi#s rmÎanual:LeqachchaptUe rstartsonaf*reGshpage,9itstitUleapp#eqarsintUherurnningheqadofallitspageGs,9andallchaptUe rKtitUleGsarecollectUedintUhetableofcontUents.n(StylechanrgeGssuchasemployeGdintUhi#smÎanualareeqasytroobtain,Ys#incetUhestylei#snotdTetUe rmineGdbytUheCWEBrsystUem,YburtratUhe rbyas1eparatUeformÎatcons#istinrgof^TU>'ExXmÎacroqs;ctafewsmallchanrgeGs^tostandrardformÎatcanchanrgetUheove rallapp#eqaranceoftUhedoGcurment,anditwouldb#eequallyeqasytrochanrgeforinstancetUhepages#izeortUhesym|qbGolsus1edtrorepres1entop#e ratrors.) The reji#soneimpGortantpGointlefttroexplainabGouttUheexample,whichi#stUhesp#ecialpGoqsitionoftUhelineGs ՠn썍CWEBxMANUALWHAJTXACWEBPRÎOGRAMLOOKSLIKE9n@PstartinrgOwitUh#de n9e/Hand#include27.`AltUhÎoughtheyloGoklikeordinÎarypreproGcesqsorOlines,;whichOcould haveotUhe rcompilationurnits(andevenbytUheprogramproGduced>asmÎainourtʪput).RIt>allowsoneforinstancetrostatUefunctionprototyp#edTeclarationstUhatgotrotUheheqadTe r leandtUhemÎatchinrgfunctiondTe nitionsintUhe%C program%intheimmeGdiatUevicinityofoneanotUhe rwitUhintheCWEBѦdoGcurment.aThemoGdulewitUhthe lenÎameلcanrefe rtrosuUbmoGdules,HandلsoontroanydTeptUh,HjustliketUhemoGdulesلcontr*iburtingلtotUhemÎainoutʪput.Thi#sqpGoqssibilityqshÎouldbeus1eGdwitUhsomerestrainthÎoweve r,&9lestqreqadTersqhavediculrty ndinrgouttowhich le~/tUheprogramf*ragmentdTe neGdbysomemoGdulewillb#es1ent.VThepreproGcesqsor~/lines~/tUhatarehandleGdbyCWEBswillnormÎallyonlyb#ecomepartoftUhemÎainprogramourtʪput,"notofanyadditionÎalourtʪput leGs;JtUhi#sprovidTeGsKonevqalidreqasonforsometimeGsbypasqs#inrgtUhef#acilitieGsofCWEBr,andincorpGoratinrg#de n9e/&and#include1alsetup The^:programme rcreqatUeGsaplaintext leus#inrgtUheformÎatexplaineGdb#elow,swhichcontainsnbGotUhprogramf*ragmentsandcommentary*,andhas lenÎameextUens#ion`.w b';!fe.g.,tUhe lef*romwhichtUhe};exampleabGovewasproGduced};i#scompare.w6ë(itisincludTeGdintUheCWEBx!ϫdistr*iburtion).xThe};CWEBҫsystUemcons#istsoftwourtilityprograms`CTANGLE%FS'and`CWEAVE V'tUhatcanb#eapplieGdtrotUhi#ssource le.WInordTe rtocreqatUeTanexecurtableTprogram,onei#sqsueGstUhecommÎand`ctangle?compareOF;',whichwillreqadtUhe lecompare.wandwr*itUea lecompare.c6containinrgtUhecorreGspondinrgڬC program.UThi#s lecantUhenb#eproGcesqs1edintUheordinÎaryX(waybyanyC^compile rtroproGduceanexecurtableprogram.zAT*oproGduceapr*intUeGddocurmentontUheսothe rսhand,onei#sqsueGstUhecommÎand`cweave?compareJ>',whichwillagainreqadtUhe lecompare.w3 ,andtUhi#s4.(Thi#s les1e rveGsasinpurtfortUhetyp#eGs1ettinrgprogramTU>'ExX:bygivinrgtUheOcommÎand`tex?compare:FG'itwillb#eproGcesqs1ed,oandtUhereGsulrti#sa lecompare.dvi>K.^This lecanbeeGitUhe rpreviewedorconve rtUedtrohardcopyoutʪputbytUhesystUemdTep#endentprogramsfortUhi#spurpGoqs1ethataccompanyaTU>'ExX.DeGspitUetUhesomewhatelabGoratUeprocesqs#inrgtra8jector*ieGs,itwillb#ecomeapparenttUhattUheprogramme rUUhasgoGodcontrolove rtUhe nÎalreGsulrtproduceGdinbotUhcas1es.  Aword&ofexplanÎationabGourttUhenÎameGsofCWEBanditsconstituentprograms.]bTheinitialCދ'sstandfortUheprogramminrg@language,ëofcours1e;tUhereGstoftUhenÎameGsaretUhesameastUhÎoqs1echÎoqs1enbyKnUurthfortheor*iginÎalWEBͫsystUemn(whichexi#stUeGdlonrgb#eforetUheW*orldWidTeWeTb).nTheCWEB8lanrguageallowsonetros1eparatUelydTeGsTcr*ib#eTsmÎallpartsofaCXprogramandtUheGirintUe rconnections,bGotUhformÎal(viamodulerefe rences)andinformÎal0V(bysomes1emÎanticrelationship);witUhsomef#antasytUhi#sevokeGstUheimÎageofaweTbofconnectUeGdpieceGs.i0Thes1e#partsarelineqar*i#s1eGdquitUedi e rentUlyintheGirpres1entation#forhUurmÎanreqadability#tUhanintUhe\ocial"forminwhichtUheyarepreGs1entUedtrotUheC ҫcompile r,landiti#stUheprogramCTANGLE,}tUhatdo#eGstUhesomewhatJcomplicatUeGdreordTe r*inrgtoobtaintUhelattUe rf*romtUheforme r.Thi#sproGcesqsi#straditionÎallycalled\tanrgling" tUhecoGdTe,8[alrtUhÎoughonecouldalsocalliturntangling ifoneprefe rsformÎaltrohUumÎanordTe r.TheCWEAVE#1programintUe rtwineGstUheTU>'ExXandC partsoftUhesourcetUextand\weqaveGs"tUhemtrogetUhe rlikewarpandweft,reGsulrtinginab#eqautifullyformÎattUeGddocurment.DDespitUetUhes1eprettymetaphÎors,youwillb#eforgivenifUUyousometimeGsgettUheGs1enÎameGsmixedup. Thi#sʄgene ralorganisationofCWEBdhassomeimmeGdiatUecons1equences.TFirstʄofall,'oneneeGdstrohavean'*op#e rationÎalTU>'ExXsystUemand(notsurpr*i#sinrgly)aCcompile rinordTertrous1eCWEB;tUheCWEB԰programsformonlyacomparativelysmÎallpartoftUheurtilitieGsneeGdTed.\tSecond,tUheCWEBzlanrguagemustb#esuchtUhatbGotUh vqalidCLcodTeandTU>'ExXinpurtcanb#ede r*iveGdmechanicallyf*romit,xwhichareratUhe rdi erentformÎats.Neve rtUheleGsqstheCWEBlanrguagei#squitUesimple:NtUhisisbecaus1eforalmoqstalloftUheCWEBsourcetUexttherequireGdQ1formÎati#seitUhe rthatofTU>'ExXorthatofC g.e\ThemÎainfurnctionoftUhesp#eci cCWEB(commÎandsi#stroEstructuretUhesource leanddTetUe rminewhichpartsoftUheinpurtwillb#eproGcesqs1edfurtUhe rinwhatway*.FinÎally*,asomewhaturnfortunÎatUecons1equenceofCWEBDM'ssetupi#stUhate rrorsmÎayb#edTetUecteGdbyanyoneofCTANGLE%FS,DtUhe퀬C 6compile r,CWEAVE%andTU>'ExX.TheknowleGdgeabGourtC 6andTU>'ExXbuilrtintotUheCWEBa\programsi#sf#ar"df*romsucienttroensuretUhattheywillalwaysproGducee rror-f*reeourtʪput"dcoGdTe,,altUhÎoughofcours1etheydotUheGirb#estnottrointroduceanye rrorstUhems1elveGs.&Abr*ightpGointintUhecas1eofC тe rrors,i#stUhattUhe#lin9edirectiveGsproduceGdbyCTANGLE-;enÎabletUhecompile rtroreferdirectUlytrolineGsintheCWEB{source leinitse rrorsUUmeGsqsages,ratUhe rthantrotheintUe rmeGdiateUUC X leUU(burtTU>'ExXdo#eGsnothaveUUasimilarfacility). It]followsf*romtUheGs1ef#actstUhattUheCWEBAprogramme rmUustb#eacquaintUeGdbotUhwithCi֫andwithTU>'ExX;hÎoweve r,tUhedTepthoftheknowleGdgerequireditnottUhesameinbGotUhcas1es.'Obviously*,onecannotwr*itUeacompurtUe r{programwitUhÎoutagoGod{undTe rstandinrg{oftUheprogramminrglanguageus1eGd,tbutave rysup#er cialknowleGdge>ofTU>'ExXwillsuce:inmoqstcas1esnoTU>'ExXp#e rtis1e>beyond>tUhebas#icfactsinchaptUe rs>2{6ofTheTU>'ExXbGooki#sRrequired(burtpleqas1edon'tskipchaptUe r2,asonlytroGomÎanyp#eoplehavedone).iThereqasonforYtUhi#sistUhatonerarelyneeGdstroinstructTU>'ExXtrodosophi#sticatUeGdformÎattinrg.iIti#struetUhattUheprop#e rtyp#eGs1ettinrg$rofcomputUe rprogramsi#sasuUbtle$rmÎatte r,X8burtiti#sprecis1elytUhisparttUhatistaken$rcareofbyCWEAVE#(evenforrefe renceGstroC constructsintUhecommentary),]andtUheprogramme rcanjustconcentratUe Tn썍CWEBxMANUALٚHOÎWXTOCREAJTEACWEBPROGRAM11n@Ponwr*itinrgsyntacticallycorrectChcoGdTe.OntUheotUhe rhandtUhefullpGowe rofTU>'ExXi#savqailableifonewi#sheGs tro|us1eit,͆forinstancetoilluminÎatUetUheprogramwiththinrgslikecomplicatUeGdtableGs,͆ormÎatUhformulaeofadi e rentUUnÎaturetUhantUhÎoqs1eoGccurr*inrginacomputUe rprogram. SincetUheCWEBcommÎandsdTeqalonlywitUhthestructureoftUhesource le,$,notwitUhitscontUents,$,tUheycanb#eve ry&br*ief:4tUheycons#istof`@e'followeGdbyoneotUhe rcharactUe r,andarecommonlyrefe rreGdtroascontrolcodTes.F*orinstance,`@ b'(i.e.,`@e'followeGdbywhitUespace)indicatUeGstUhestartofanews1ection,and`@c b'mÎarkstUhestartoftUheC partofas1ectiontUhatcontr*iburtUeGstotUheunnÎameGdmodule.WControlcodTesmÎayplacedatanypGoqs#itionwitUhinthesourcelineGs,alrtUhÎoughiti#scustomÎarytoplacetUheoneGsdTe ninrgtUhecoars1estructureoftUhesourceC leattUheb#eginninrgofalineforb#ettUe rvisibility*.[lInsomecas1eGsacontrolcodTemÎarkstUheb#eginninrgofa(pieceoftUexttUhatwillb#einte rpreteGdbyCWEBinasp#ecialway*,asforinstance`@< b'whichstartsamoGdulenÎame;tUhekendoftUheGs1econtroltUextsHi#salwaysmÎarkeGdbytUhesp#ecialcoGdTe`@> b'.JyThecharactUe r`@e'wass1electUeGdb#ecaus1eWitisquitUeurncommonbGotUhinC ]XandinTU>'ExXsourcecodTe,X burtintUhÎoqs1ecaseGswhe reonedo#eGsneeGdtropasqsUUontUhecharactUe rits1elf(e.g.,inC Xstr*inrgsandcomments)itshÎouldb#ewr*ittUenas`@@ b'. W*e nowdi#sTcusqstUhevqar*iouscontrolcoGdTes,group#ed bytUheGirfurnction.He reweshalltreqatonlytUhemoqstimpGortant[controlcoGdTes,whichareus1edregularlyinordinÎaryprograms.9T*reqatmentofanUurm|qb#e rofadditionÎalcontrolcoGdTes,מtUhateitUhe rs1ervefor neturninginsp#ecialcas1eGs,מorareintUendTedtroalloweme rgency xeGsinurnforeGs1een&scases,/i#s&sdTefe rredtroalatUe rs1ection,/inordTernottroconfus1enoviceCWEBBuse rs.b&F*ortUhecoGdTes&sthatare]!di#sTcusqs1eGd,_wedohÎoweve rprovidTefulldetailsoftUheGirus1e;amoqstoftUheGs1ecanb#eskipp#eGdon rst]!reqadinrg.AUUsurmmÎaryofallCWEB1controlcoGdTesUUcanb#efoundantUheendoftUhi#smÎanual.\Sei>ctioningcodes:)o`Ka@* Q',M`Ka@',`Ka@~' ThemoqstimpGortantcontrolcoGdTesaretUhÎoqs1ethatsp#ecifythedivi#sionofLtUheCWEBFprogramintros1ections.The rearetUhreecoGdTesLthatindicatUetUhestartofanews1ection, andaretUhe reforecalleGds1ectioninrgcoGdTes.eEachoftUhemhasaslightUlydi e rente ect,%bandeqachs1ectionmUuststartwitUhɢoneofthem(i.e.,as1ectioni#sneve rimplicitUlystartUeGd).ήThetUhrees1ectioninrgcoGdTesɢare`@* b',`@',and`@~ b',A~of'ExXZtUexttUhatfollowsi#signoreGd,[0aslonrgastUhe rei#snocompletUelyblankline(whichTU>'ExXwouldintUe rpretastUheUUendoftUheparagraphtUhatstartUeGdwitUhthes1ectionnUurm|qb#e r). As1ectionstartinrgwitUh`@* b'willstartanewchaptUe roftUheCWEBdoGcurment;itshÎouldb#efolloweGdbytUhetitUleofthechaptUe r,Ewhichi#stUe rminÎateGdbytUhetwo-charactUe rs1equence`. b'(againtUhespacemightb#eanywhitUespacecharacte r).-ThetitUlei#snotrecognis1eGdbyCWEBitself,^burtratUhe rbyTU>'ExX,asadTelimitUeGdmÎacroargurment^y*.3Thi#symeqanstUhatifonewantstrohaveanoGccurrenceoftUhes1equence`. b'intUhetitUleits1elf,Bthi#scanwb#eachieveGdwbyencloqs#inrgtUhetitUle(burtnotthe`. b'tUe rminÎatinrgit)inbraceGs..IfonewantstroputotUhe rtUhinrgs}thanplaintUextinachaptUe rtitUle,oneshÎouldb#eawaretUhatiti#sconve rtUeGdtroupp#e rcas1eintUherurnningheqads/WofpageGsandalsowr*ittUentrotUhetableofcontUents/W le;XonlyitemstUhatb#ehaveprop#e rlyurndTe rtUheGs1eop#e rationsshÎouldbeus1eGdinachaptUe rtitUle.0-Aqpartf*romi#sqsuinrgatitUlethatwillapp#eqarins1eve ralplaceGs,as1ectionstartinrgachaptUe rwillforceapagebreqakb#eforeit,anditwillcaus1etUhes1ectionnUurm|qb#e rtob#epr*intUeGdonUUtUhetUe rminÎaldur*inrgtUheexecurtionofCTANGLE+andCWEAVE#[,asaprogreGsqsreport. AsafeqatureforadvqanceGdus1e rsofCWEB,HsomeextrainformÎationmÎayb#esupplieGdwitUhthe`@* b'controlcoGdTe:if!Liti#simmeGdiatUelyfolloweGdby`*e'orbyadTecimÎalnUurm|qb#e r,+than!Lthi#sisnotincludTeGdintUhechaptUe rtitUle,+burtratUhe rhEintUerpreteGdhEasanindicationhEoftUhe\level"oftUhechaptUe r.HerehE`@**F_'indicatUeGstUhestartofagroupinrgof8s1ectionsevencoars1e rtUhanachaptUe r,)>andtUhegroupinrgstartUeGdby`@*n'b#ecomeGs ne rasnincreqas1eGs,)>witUh`@*0F_'ucorreGspondinrgtounÎador#neGd`@* b'.Thee ectoftUhi#sleveldTep#endsontUhedTe nitionoftUheTU>'ExXmÎacroqstUhatformÎattUhechaptUe rtitUleandtUhelineGsintUhetableofcontUents,c`\N b'reGsp#ectively`\contentslineDA',ctrowhichtUheleveli#spasqs1eGdas rstargurment(for`@**F_'tUheleveli#s1);Ritcoulde ectforinstancetUhefontus1eGdfortUhe|chaptUe rtitUleortheamourntofindTentationoftUhattitUleinthetableofcontUents.IIntUhedTef#aulrtde nitionsofetUheGs1emÎacroqstheleveli#slargelyignoreGd,hexcepttUhat`@*n'willnotforceapagebreqakforn@s,hwhe reesi#sUUtUhevqalueofthe`\secpagedepthDA'regi#stUe r,whichi#ss1etinitiallytro2. off= V^y The refore,&ifnocorrectUlysp#eci eGdtitUlefollows`@* b',&tUhenCWEAVE(Jwill ndnotUhinrgwrong,&butTU>'ExXwillcomplain abGourta\RqunÎawayargument"ofamÎacrotUhattUheprogramme rdidnotexplicitUlywr*itUe(nÎamely`\N b');UUtUhi#sisoneoftUhesTcar*ie rerrormeGsqsagetUhatnoviceus1e rscancomeacroqss,UUsopleqas1eb#ewar#neGd. Dn썫12HOÎWXTOCREAJTEACWEBPROGRAMٚCWEBx6KMANUALn@P In9contrasttro`@* b',ras1ectionstartinrg9witUh`@~ b'instUeqadof`@ b'willtieits1elftrotUhepreviouss1ection,rin tUhe$s1ensetUhatapagebreqakb#etweentUheGs1esectionswillb#eavoidTeGd.5Morepreci#s1elytUhisiswhathapp#ens:normÎallyCWEAVE';willinstructTU>'ExXtrobreqakpageGsonlyb#etweens1ections(exceptwhenonei#stroGolargetoGo tlonas#inrglepage)andputasmÎanys1ectionsoneqachpageaspGoqss#iblelsuUb8jecttrothi#sreGstr*iction;x'hÎoweve r,as1ectionstartinrgwitUh`@~ b'willb#econsidTe reGdtrobecontinUuationofthepreviouss1ectionfortUhepurpGoqs1eofpage1breqakinrg.'A1s#ituationwhe reonewouldus1e`@~ b'i#stUhefollowinrg:*suppGoqs1ewedTe neafurnction,handalso9wanttrostatUeitsprotrotyp#e,>whichwillb#elonrgtoadi e rentmoGdule,>s#inceithastroapp#eqarearlie rintUheprogramuorevenonas1eparatUe(heqadTe r) le.AunÎaturalplacetrogivetUheprotrotyp#eintUheCWEBqdoGcurmenti#sdirectUly`b#eforethefurnction,sotUhatitcaneqas#ilybes1eentUhattheprotrotyp#emÎatcheGstUheactualdTe nition.NowwitUhÎourtsp#ecialmeqasureGstUhe rei#sasuUbqstantialchancetUhatapagebreqakwilloGccurb#etweentUheGs1etwos1ections,I s#inceEtUheshÎorts1ectionwitUhtheprotrotyp#emight tonanalreqadypartially lleGdpage,I whe reqastUhelarge rhcs1ectionwitUhthedTe nitionmightnot.BystartinrgtUhelattUe rs1ectionwitUh`@~ b',m&itcanb#eachieveGdtUhatinUUsuchcas1eGstUheforme rs1ectioni#smoveGdtrogetUhe rwitUhthelattUe rtrothenewpage. D Like\anyotUhe rs1ectiontUheve ry rsts1ectionstartswitUhss1ectioninrgcoGdTe(usually`@* b'),]andanytUexttUhatmightrMpreceGdTeiti#snotpartofanys1ection;tUhi#stUextissaidtrobe\inlim|qbGo".ȮThismÎatUe r*ialisignoreGdby2CTANGLE)y5,jFand2copieGdlitUe rallyintrotUheTU>'ExX lebyCWEAVE(l(exceptfortUhereplacementof`@@ b'by`@e'),followinrgtUhe rstlinewhichalwaysreqads`\input?cwebxmacOF;'(inordTe rtroloadtUhestandrardformÎat).ThepurpGoqs1eoftUhetUextinlim|qboi#stroallowisqsuinrgTU>'ExXcommÎandstUhatapplytrotUhewhÎoledoGcurment(suchasmÎacrodTe nitions,+pGoqss#iblymoGdi cationsoradditionstrotUhestandrardformÎat),+orproGducinrgatitUlepageoranDintroGductionpreceGdinrgtUhes1ectionsoftUheCWEBdoGcurment.?NocontrolcoGdTesarealloweGdintUhelim|qbGotUextu(well,}almoqst;tUhe rearetwoexceptions,}tUhatwillb#ementioneGdb#elow).Thelasts1ectionendss#implyattUhe~endoftUheCWEBXsource le;tUhe rei#snowaytroaddmÎatUe r*ialafte rit(orels1ewhereourts#idTetUhes1ections).Howeve r,= CWEAVE&zZwill6app#endsomemÎatUe r*ialattUheendits1elf(urnleGsqsiti#sinvokeGdwitUha`-x b' ag):banindTexofQidTenti e rus1eGs,ali#stofmodulenÎameGs,andatableofcontUents.Becaus1eQtUheindTexi#ss1eqamleGsslyQattacheGdtro@tUhelasts1ection,{Piti#scustromÎarytogivetUhats1ectiontUhetitUle\IndTex"andnottroincludTeanyprogramf*ragmentUUinit.?Subsei>ctioningcodes: `Ka@d Q',`Ka@h',`Ka@f',`Ka@c',`Ka@<?:::I@>=3' Eachs1ection,asdTelimitUeGdbytUhes1ectioninrgcoGdTes,contains/aTU>'ExXpart(alrtUhÎoughitmayb#eempty),and/inadditionatmoqstoneC ޔpart,whichalwayscomeGsattUheendoftUhes1ection,andze roormoreintUermeGdiateparts,ofwhichtUhe rearetUhreekinds:tUhÎoqs1etUhat sp#ecify#de n9e. and#include5 {directiveGs,vandformÎatdTe nitions(s1eeb#elow).*IntUe rmeGdiate partscanb#e]giveninanarbitraryordTe r,aslonrgastUheycomeaftUe rtUheTU>'ExXpartandb#eforetUheC part,ifpreGs1ent.MTheb#eginninrg@ofanypartotUhe rtUhantUheTU>'ExXpart(whichstartsdirectUlyaftUe rthes1ectioninrgcoGdTe)i#smÎarkeGdbyant>appropr*iatUecontrolcoGdTe,{whichi#scalleGdasuUbqs1ectioninrgcoGdTe;tUhes1et>codTesareoptionÎalt>intUhes1enset>thattUheytkneeGdonlyb#egiveniftUhecorreGspondinrgparti#spres1ent.TheendoftUheTU>'ExXparti#sdTetUe rmineGdbytUhe rstUUsuUbqs1ectioninrgcoGdTe,orinabqs1enceofanyoftUhembytUhenexts1ectioninrgcoGdTe. TheC part,8ifpreGs1ent,b#eginsattUhe rstoGccurrenceof`@< b'or`@c';tUheforme rstartsadTe ninrgoGccurrenceofȬamoGdulenÎame,andtUhelattUe ri#sus1eGdwhentUheC ?partb#elonrgstotUheunnÎameGdmodule.BTheȬcodTe`@c b'mÎayalsob#ewr*ittUenas`@C b'(infactallalphabeticcoGdTesareequivqalenttrotUheirupp#e rcas1ecourntUerparts).JKOncetUheC kIpartofas1ectioni#sstartUeGd,anyfurtUhe rmoGdulenÎameGsareintUe rpretedasmodulesrefe rencesratUhe rthanas"dTe ninrgoGccurrences.VA"Pmodule"nÎame,UwhetUhe rdTe ninrgornot,Ucons#istsofTU>'ExXcoGdTebetweentUhe`@< b'andtUhenextoGccurrenceof`@> b'.eAsameqasureagainstaccidTentalmi#sintUe rpretationofmoGdulenÎameGs,%cduefor9instancetroaforgottUen`@ b'or`@c',?DtUhecloqs#inrg`@>'ofadTe ninrgoGccurrencemUustb#efollowed9(optionÎallywitUhHsomewhitUespaceinb#etween,burtnonewline)byoneof`=e',`== b',`+='Hand`+==F_',whileforanon-dTe ninrgoGccurrence!tUhi#smustnotb#ethecas1e.+ThepGoqss#ibilitieGs!`+= b'and`+==F_'areincludTeGdfortUhÎoqs1ewholiketUheGirsourceGcoGdTeforcontinUuationsGofmodulestrores1em|qbletUhepr*intUedourtʪput,butGtUhedi#stinctioni#signoreGdbyCWEB\:Iit{wills#implypr*int`'aftUe rtUhe rst{dTe ninrgoGccurrenceofamodulenÎameand`+'aftUe ranyfurtUhe rdTe ninrgUUoGccurrences. The_suUbqs1ectioninrgcoGdTestUhatmÎarktheb#eginninrgofintUe rmeGdiate_partsare`@d b',`@h',and_`@f'.OftUheGs1etUheZ rsttwosp#ecifypreproGcesqsordirectiveGsforresp#ectivelyamÎacrodTe nitionandtUheinclus#ionofaheqadTe r le,,/and!tUhelastsp#eci eGsaso-calledformÎatdTe nition.`ThecoGdTes`@d b'and`@h'willb#ereplaceGdby#de n9ereGsp#ectivelyby#include5M'inbGotUhtheprogramandtUhepr*intUeGddocurment.dW*ealreqadymentioneGdhÎowtUhee ect0^ofus#inrg`@d b'or`@h'di e rsf*romtUhatofus#inrg#de n9e/or#include6H%directlyintheCpartofthe kn썍CWEBxMANUALٚHOÎWXTOCREAJTEACWEBPROGRAM13n@Ps1ection:}tUhe^0directivewillb#emoveGdtrotUheb#eginninrgoftUheC j le,`gandincas1eof`@h b',`gtUheheqadTe r lewillb#e sTcanneGd2fortyp#eGdTefde nitions.JfHe rewementionafewmorepGointstUhatarerelevqantwhenwr*itinrgtUhesource le.  MacrogdTe nitionsfollowinrg`@d b'arenotline-or*ientUeGdliketUhÎoqs1einC :eve rytUhinrguptotUhenextsuUbqs1ectioninrgorks1ectioninrgcoGdTei#sconsidTe reGdtrobelonrgtotUhemÎacro,qandnewlineGsneeGdnotb#eesTcap#ed,qasCTANGLE,gwilltakecareofeGsTcapinrganynewlineGswhilewr*itinrgtotUheC^ le.[The rearesomemildreGstr*ictionsontUhereplacementptUextofa`@d b'mÎacrodTe nition:parentUheGs1espandbraceGsshÎouldb#ebalanced(tUhi#sisadTelibe ratUerequirement,mÎadTeZinorde rtroallowdetUectionofprogramminrge rrorstUhatwouldotUhe rwi#s1ebeve ryhardtrotrack;mtUheesamerequirementalsohÎoldsforeqachcompletUeC y:partofas1ection),iandnomoGdulenÎameGsshÎouldb#erefe renceGd.ItisnotpGoqssibletrous1eotUhe rpreproGcesqsordirectivesinmÎacrodTe nitionseGitUhe r,burttUhati#sb#ecaus1ectUhisisalreqadyimpGoss#ibleinC U.$AftUe ra`@h b'commÎand,fatleastonenewlineshÎouldoGccurb#eforetUhenextUUs1ectioninrgorsuUbqs1ectioninrgcoGdTe. 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TheFmheqadTe r lesp#eci eGdaftUer`@h b'its1elfshÎouldofcoursecontainordinÎaryC ;coGdTeratUhe rtUhanCWEB6inpurt;aftUe rall,ղitwillb#ereqaddirectUlybytheC ȫcompile r.'ExXmÎacroqs; XtUhementioneGdidTenti e rswilltUhe reforeb#ewr*ittUen-trotUheTU>'ExX leas`\TeX\'reGsp#ectively`\NULLY',5"whichcaus1eGstUhemtrob#etyp#eGs1etas`TU>'ExX'- resp#ectively` '.`Thi#smechanismgiveGstUheus1e rtUheabilitytrochanrgetUheapp#eqaranceofidTenti e rsinanydTeGs#iredway*,s#implynbydTe ninrgtUhemÎacroappropr*iatUely*.TheclasqsofT;eX`׫i#sintUendTeGdforidenti e rstUhatarestillalpha-b#eticinapp#eqarance(pGoss#iblywitUhlettUe rsbeGinrgaccentUedorshiftUed),%whiletUheclasqsofNULL"Ri#sintUendTeGdforidTenti e rstUhatarerepreGs1entUedbymÎatUhematicalsym|qbGols.bHencetUheTU>'ExXmacrowillb#eproGcesqs1edinhor*i-zontalWmoGdTewitUhitalicfonts1electUeGdintUhe rstWcas1e,andinmÎatUhmoGdTeinthes1econdcas1e.OSimplysayinrg`@f?alphaNULLDA'FsuceGstromÎakealphapr*intas z;KtUheformÎatdTe nitioni#styp#eGs1etas`form}aft$alpha@@ ( z)`'troUUmÎaketUhecorreGspondTenceUUoftUheidTenti e randtyp#eGs1etsym|qbolevidTent. 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Themoqstobviousus1eof`@; b'i#sintUhecas1ealreqadymentioneGdofamÎacroinvoGcationtUhatexpandstroa(compGournd)?statUement:placing?`@; b'aftUe rsuch?amÎacroinvoGcation?willcaus1eittob#erecognis1eGdasastatUementbyCWEAVE#׫,!Lkeepinrgitspars1e rhappywhilenota ectingtUheactualC8program.[KThe reareotUhe rs#ituationsas0wellwhe reonedo#eGsnotwanttroplaceas1emicolon,gnyetwi#sheGsCWEAVE(gtroactasifitwe retUhe re.IfamÎacropstandsforstatUementtUhathapp#enstroendinas1emicolon,7tUheniti#sagoGodidTeqatrosuppresqstUhe nÎals1emicolonintUhedTe nition:RintUhatcas1eallinvoGcationscansupplytUhes1emicolon,andonedo#eGsnothavetroremem|qb#e rwr*itinrg`@; b'instUeqadof`;e'attUheinvoGcationsoftUhi#smÎacro.F*orinstance,"tUhemÎacroreplacementtUextcouldb#e`dohstatementiG~fwhilee@(hconditioni3t)',or`if 3v(hconditioni)hstatUementi:ǧels9?ePhexpreGsqs#ioni-',oreven`if si(hconditioni3t)hstatUementi;Gels9?eNY', whe retUhe nÎalels9?e9wasplaceGdwitUhthepurpGoqs1eofpickinrguptUhefollowinrgs1emicolonasanemptystatUement;"inalltUheGs1ecaseGstUhemÎacroinvoGcationtrogetUhe rwitUhthefollowinrgs1emicolon i#sacompletUestatement tUhatcanb#eus1eGdwitUhÎourtspecialprecaurtion,evenastUhe rstbranchofanif_-els9?e,ǫstatUement.^9Howeve r,&eintUheGs1ecaseGstUhemÎacrodTe nitionits1elfneeGdsabitofextracare:Tqa`@; b'shÎouldb#ew$placeGdattUheendtrorepreGs1enttUhes1emicolontUhatwillfollowininvoGcations,sotUhatCWEAVE&canprop#e rlyformÎatItUhereplacementtUextoftUhemÎacro.iFinally*,'FitItUhe recanb#epurelyaeGstUheticreqasonsforwantinrgtosuppreGsqsGas1emicolonattUheendofa`|...|Y'construction,Bforinstancewhenrefe rr*inrgtoadTeclarationas`c9harjjp',whichstr*ictUlysp#eqakinrgrequireGsa nÎals1emicolontrob#ecomeadTeclaration;ЮtroletCWEAVE'UxformÎattUhi#sprope rly*,oneshÎouldwr*itUe`|char?*p@;|?D'.,`Constructionslike`ret9ur(n# home[.w b] [(hchanrgeUU lei8[.chF_]j+ Tj-}) UV[hourtʪputUU lei8.<[.c]]]whe re,squarebracketsindicatUeoptionÎality*,bve rticalbarss1eparatUealrte r#nÎativeGs,band,parentUhes1es,areus1edfor groupinrg.VkHe re?hoptionsi0Mi#s?astr*ingofoneormorecharactUe rsdTeGs#ignÎatinrgoptions,asdTeGsTcr*ib#ed?below;tUhe remÎay:b#emoretUhanonesuchstr*inrgofoptions,andtUheymÎayb#egivenb#etweenoraftUe rtUhe leGsnÎameGsinstUeqadofOb#eforetUhem,withOnodi e renceinmeqaninrg.sF*orCWEAVE'\tUhes#ituationi#sentirelys#imilar,excepttUhattUhedTef#aulrtUUextUensionfortUheourtʪput lei#s`.tex\'instUeqadof`.c b'.CommandQlineoptions ApcommÎandq#parametUe rtUhatstartswitUh`+e'or`-'andhasatleqastonemorecharactUe r,ˬs1erveGstrocontroloptionÎals1ettinrgsoftUheprogramb#eGinrginvokeGd.ThecharactUe rsafte rtUheinitialcharactUe rs`+e'or`-'dTenotUeindividualsoptionstUhataretur#neGdonresp#ectivelyo ;optioncharactUe rsarecas1e-ins1ens#itive.UTheτcharactUe r`ie'formsanexception,s#inceitisus1eGdtrosupplyastr*ingargumentratUhe rtUhantroGs1etaswitch;tUheGstr*ingi#stUheremÎaindTe roftUheoptionstr*inrg(followinrgtUhe`ie'),and`+i b'and`-i b'areequivqalent.eAllQToptioncharactUe rswillb#eaccepteGd,SburtonlytUheoneGsli#stUedb#elowhaveanye ectontUheop#e rationUUoftUheprogram.qW*elisttUheswitcheGsintUhedirectiontUhatalrtUe rstUhedTef#aulrts1ettinrg.ҍswitch4pr}'ogramgee e}'ct-b4֫bGotUhgedoUUnotwr*itUeabanne rlinetrotUhetUe rminÎal-p4֫bGotUhgedoUUnotshÎowaprogreGsqsreportontUhetUe rminÎal-h4֫bGotUhgeomitUUcon rmÎationofsucceGsqsfulcompletion-l4CTANGLEgeomitUU#lin9e"֫directiveGs,UUmÎakeC X leloGoknice-x4CWEAVEgedoUUnotattachUUindTexandotUhe rinformÎationattUheendoftUhedoGcurment+d4CWEAVEgerepGortUUf#ailuretrocompletUelypars1epiecesofC XcodTe+t4CWEAVEgewr*itUeUUtUhree leGs,withs1eparatUeoneGsforindTexandli#stofmoGdulenÎameGs+e4CWEAVEgeevenUUourtnUum|qb#e rofpageGsbeforetableUUofcontUents+i4CWEAVEgeaddUUalrtUe r#nÎatives1eqarchpatUhforheqadTe r leGs(takeGsargurment)+f4CWEAVEgeforceUUalinebreqakaftUe reachstatUement+a4CWEAVEgeforceUUallstatUementsUUtrob#eonalinebytUhems1elveGs+u4CWEAVEge\urnÎaligneGdUUbracestyle":qdonotalign`f'and`g've rtically+w4CWEAVEge\widTeUUbracestyle":qforcelinebreqaksb#eforeandaftUe r`f'+m4CWEAVEge\me rgeGdUUdTeclarationsstyle":qdonotforcelinebreqaksb#etweenloGcaldTeclarations+c4֫bGotUhgerurnUUincompatibilityUUmoGdTewitUhLevy/KnurthCWEB+s4֫bGotUhgeshÎowUUmemoryusagestati#sticsUUatcompletion++4֫bGotUhgehandleUUC ++lanrguageUUinstUeqadofCTheoptions`+d b'and`+s b'onlyop#e ratUeifCWEAVE(@0orCTANGLE--wascompileGdwitUhthepreproGcesqsorsym|qbolDEBUG1mreGsp#ectivelykSTAT\dTe nedk(witUhmoqstC ^compile rstUhi#scanbeaccomplisheGdbyincludinrgacommÎandlineUUparametUe r-DDEBUG+reGsp#ectively-DSTAT&whencompilinrgtUheCWEB1systUem). The+options`be',aT`h',and+`p'canb#eus1eGdtrocontroltUheamountofoutʪputtUhatCWEBЫwr*itUeGstotUheus1e rtUe rminÎal;UUtUhecom|qbination`-bph\'willeliminatUete rminÎalourtʪputUUaltogetUherUUwhennoe rrorsareencourntUereGd.TǠn썍CWEBxMANUAL{3INVÎOCAJTIONXOFCTANGLEANDCWEAVE19n@P They option`-l b'ofCTANGLE*8ii#sintUendTeGdeitUhe rforus1ewithbrokencompile rsordTebugge rstUhatcannothandle #lin9edirectiveGsprop#e rly*,porforcas1eGswhe retUheC  lei#sofmoreimpGortancetUhanjustasanintUe rmeGdiate le,forginstancewhentUheprogrami#stransfe rreGdtropeoplewhÎodonotwishtropracticelitUe rategprogramming.Aqpart'f*romomittinrg#lin9e%zdirectiveGsandcommentstUhatindicatUetUhes1ectionnUurm|qb#e rf*romwhichcoGdTeor*iginÎatUeGs,BanDattemptDi#smÎadTetromaketUheCԾ lemorereqadrabletrohUumÎans:theDspacingand(almoqstall)comments?oftUhesource learepreGs1e rved?intUheCourtʪput,2yand?whenmoGdules?aresuUbqstiturtUeGdintootUhe rs,indTentationOlevelsareaccurmUulatUeGd,soastoproGduceindTentationtUhatloGoksnÎatural.DouUbtleGsqslythereGsulrti#s(1notpe rfect(andlineGsmÎaygetquitUelonrg),\but(1iti#sdTe nitelymorereqadrabletUhantUheourtʪput(1normÎallyproGduced.SincelayourtandcommentsoftUhesource leneeGdtrob#epres1e rvedbyCTANGLE*,9tUhi#soptionconsurmeGsUUs#igni cantUlymorememorytUhanitscontrary*. Y TheXoption`+d b'caus1eGsCWEAVE&troi#sqsueawar#ninrgwhenitcouldnotprop#e rlypars1esomepieceofC _coGdTe;tUhi#scouldhappeneGitUhe rb#ecaus1eacoGdTef*ragmenti#sincompletUeintUhes1ensetUhatitdo#eGsnotrepres1entas#inrglecompletUesyntacticentity(asintUhe`|<=n|Y'exampleabGove,orwhenamoGdulebGodyendswitUhalab#elwitUhÎourtafollowinrgstatUement),(\orb#ecaus1etUhecoGdTei#sactuallyurnsyntactic,(\orb#ecaus1eCWEAVE&@hasb#eenfoGoledbyanurnUusual(construction.cInallcas1eGshÎoweve rtUhereGsulrtcanb#e(ve ry)badlyformÎattUeGdourtʪput,1andacorrectionshÎouldb#emadTe;&us1e rswhocareabGourttUhequalityoftUhetyp#eGs1etourtʪputareadvis1eGdtroalwayssettUhi#soption(orwatleqastwhentUhedoGcurmenti#sbeGinrg nÎalis1eGd).مSettinrgtUhe`+d b'switchi#sequivqalenttroplacingacontrolcoGdTe7 `@1 b'attUheb#eginninrgofthe rst7 s1ection;A$tUhenÎatureoftUhewar#ninrgmeGsqsages7 andpGoqss#ible7 remeGdies7 willb#eUUdisTcusqs1eGdlatUe rintUhismÎanUual. Thetwoourtʪput leGstUhattheoption`+t b'willcaus1eCWEAVE%锫trocreqatUeinadditiontroitsmÎainoutʪput le,arecalleGd,hnÎamei$d.idx'ExX le(tUhi#sistUhehardpart)tUhat proGduceswacomparablepr*intUeddocurment.٩IntUhecurrentve rs#iontUhisclaimcanonlybemÎadTeforprogramswr*ittUen@inC .v;awhÎoleheqarteGdattempttrodotUhesameforC v++֫programswouldcoqstasuUbstantial@amourntofextra$work.^ The rearesomÎanydi e renceGsintUhedTetailsofformÎattinrgb#etweenCWEBx andLevy/KnUurthCWEBtUhatGkonecannotexp#ectformÎattUeGdourtʪputtUhati#sidTenticaltrowhatwouldb#eproGducedGkurndTe rLevy/KnUurthCWEB\,UUburttogettUheb#eGstapproximÎation,oneshÎouldinadditiontro`+c b'sp#ecifytUheoptions`+uft\'. D Theoption`+s b'i#sincludTeGdbecaus1etUheCWEBaܫurtilitieGsus1estaticallyalloGcatUedmemoryareqas,whichmÎaytUhe reforewdrurnout;lus#ingtUhi#soptionwdonecans1eehÎowcloqs1eonei#strotUhelimitsofCWEB.ThemoqstimpGortantlimitUeGdMresourcestUhatitprovidTeGsinformÎationabGourtareare: (a)ThenÎametableGsinwhichCTANGLE-FandCWEAVE$.strore(alldi#stinctidTenti e rsandindTexentireGs,]~resp#ectively(module(nÎames((tUheentr*ieGs`idTenti e rs',`moGdulenÎames',and`bytUes'); !8(b)CTANGLE)G'smÎainmemory*,inwhichtUhecompletUeCprogram lepro-ceGsqs1ed?dur*inrgas#inglerunhastob#estoreGd,Dalb#eit?inacompacti eGdform(`replacementtUexts'and`trokens');(c)0CWEAVE#7's0croqss-refe rencememory*,8inwhichalltUhedratafortUheindTexandli#stofmoGdulenÎameGsarestrored(`croqss-refe renceGs');4 (d)Hitspars#inrgbu ers,whichmUustb#eabletrohÎoldanyoneprogramf*ragmentorpieceofC(coGdTe(`sTcrapqs',`tUexts',and`trokens').The reshÎouldb#enoimmeGdiatUeneeGdtroincreqas1etUhes#izeoftUheGs1ememorymareqas,ss#inceevenfortUhemÎainprogramofCWEAVE#st,stUhelargeGstofCWEBz'sowncompilationurnits,stUheus1eofanyoftUheGs1eresourcesi#slesqstUhanathirdoftheamourntavqailable.bThe rei#sonereGsourceofwhichalarge rqf*ractioni#sus1eGd,+8nÎamely`tr*ienoGdTes',+8burtqitsusagedep#endsonlyontUhes1etofgrammÎarruleGsuseGd,which i#sindTep#endent oftUheparticularCWEB vsource le.Whenforsomesource leCWEB vi#sapproachinrgitslimits,oneG9canofcours1etrytrorecompileCWEBΫwitUhlarge rarrays,burtaltUe r#nÎativelyG9onemÎayreGstructuretUhe source le:fwhenoneof(a),(b),6or(c)rurnsout,6onemightcons#idTe rbreqakinrguptUhe leintros1eve rals1eparatUely/proGcesqsed/pieces;guments Any/commÎandlineargurmentstUhatdonothavetUheformofanoptionaretakentroindicatUe lenÎameGs;5JtUheirnUurm|qb#e rcanvqaryf*rom1to3.1The rstonesp#eci eGstUhemÎainsource le,tUhes1econd*(ifpreGsent)indicatUeGstUhechanrge le,`andtUhetUhirdoptionÎallydTe neGsanon-standrardnÎamefortUhemÎain$ourtʪput le.GbThecontUentsandfurnctionoftUhechanrge lei#sdisTcusqs1eGdintUhenexts1ection;he rewewejustindicatUehÎowtUheactual lenÎameGsus1edaredTe r*ivedf*romtUhegiven lenÎameargurments.QAsf#arasCWEB isconce r#neGd]a lenÎamei#scompGoqs1ed]ofabasenÎameandanextUens#ion.LoGoqs1elyspeqakinrg,`(tUheextUensionoftUhemÎain ledTef#aulrtsto`we',tUhatofthechanrge leto`ch b',andtUhatoftUheourtʪput leGstro`ce'or`texF_'forCTANGLEreGsp#ectivelypCWEAVE&ޫ(burtps1eealsotUhedisTcusqsionoftUhe`++ b'optionabGove);~|tUhebas1enÎameGsoftUhechanrge leand{tUhemÎainourtʪput ledTef#aulttotUhatofthemÎain le.:Ifinplaceofachanrge lenÎameanargurment`-e'i#sspeci eGd,,nochanrge lei#sus1eGd;alsoifonlyone lenÎameargurmentwasgiven,,oriftUhechanrge lenÎamewasTsp#eci eGdas`+e',TUtUhentUhedTef#aulrtchanrge lenÎamei#str*ieGd,TUburtifnosuch leexi#sts,TUproGcesqsinrgTproceedswitUhÎourtJachangeJ le.n(Sp#ecifyingtUhechanrge leas`+e'i#sonlyus1efulifatUhird lenÎameargurmenti#sgiven.)The refore,asqsurmingregularnÎaminrgconventions,tUhe rei#snoneeGdtrosp#ecifymoretUhantUhemÎain lenamewitUhÎourtUUextUens#ion,whethe rUUornotachanrgeUU lei#sbeGinrgus1ed. The=6preci#s1eruleGsareasfollows.)jOn lesystUemswhe reanextUens#ionisnotastandrard=6prope rty=6of lenÎameGs,.5like$mtUhatofUNIXJ,.5iti#sasqsurmeGdtUheap#e r*ioGdisavqalidcharactUe rin lenÎameGs;4afull lenÎamei#stUhenformeGdbyconcatUenÎationoftUhebas1enÎame,`ap#e r*ioGdandtUheextUens#ion(notetUhatthi#simplieGsthatonsuchsystUemsCWEBdcannotacceGsqs leswhÎoqs1enamecontainsnop#e r*ioGdatall).Conve rs1ely*,Hastr*inrgdTeGs#ignÎatinga1Zfull lenÎamei#sbrokenupintroabas1enÎameandanextUens#ionattUhelastoGccurrenceofap#e r*iod;\ifnop#e r*ioGdispreGs1ent,tUhenthestr*inrgi#stakentrosp#ecifyabas1enÎameonly*,andi#ssaidtrohavenoextUens#ion.QIftUhe1 rst lenÎameargurmenthasanextUens#ion,gitspeci eGsbotUhbas1enÎameandextUens#ionoftUhemÎainsource le,}otUhe rwi#s1euitspeci eGstUhebas1enÎame,}andtUheextUens#ionistakenutrobe`we'(ifnosuchu leisfournd,}tUhen썍CWEBxMANUAL>SUBSIDIARJYXINPUTFILESANDCHANGEFILES21n@PextUens#ion`webF_'isalsotr*ieGd,(burttUhisfeqatureisobqsoletUe).'Thebas1enÎameoftUhemÎainsource lei#salsotUhe dTef#aulrtubas1enÎameoftUhechanrge leandtUhemÎainourtʪputu le;tUheGirdTef#aulrtextUensionsareasdTeGsTcr*ibeduabove.If'yas1econdandpGoqss#ibly'ytUhird lenÎameargurmenti#spreGs1entandi#snot`+e'or`-',0itove rr*idTeGs'ytUhebas1enÎame,and%-alsotUheextUens#ionifithasone,.oftUhechanrge lereGsp#ectivelyoftUhemÎainourtʪput%- le.aNochanrge lewillb#e89us1eGdeitUhe rifthes1econd lenÎameargurmenti#s`-e',> orifnochanrge lei#sfoundwhentUhes1econd lenÎameargurmentUUi#s`+e'orabqs1ent.R6SuTb s(idiaryTinput leQsan9dchange leQs\AsewehavedTeGsTcr*ib#edeitsofar,tUheCWEB &troGolsreqadasinrglesource le,f*romwhichamÎainoutʪput leandpGoqss#ibly someauxiliaryourtʪput lesareproduced.]Since C Hprograms canb#ebuilrtf*roms1eve ralcompilationurnits,^it\i#snotuncommontUhats1eve ralCWEB@Tsource leGscontr*iburtUeindTep#endentUly\trothesameprogram,^andtUhe remightb#enon-CWEB 5source leGsaswell.RHoweve r,yevenwhati#sconceptuallyas#inrgleCWEBsource,dTeGsTcr*ib#edbyasinrglepr*intUeGddocurment,)mÎayinf#actbecompGoqs1edf*romseve ralinpurt leGs._Twomechani#smsare providTeGdforcom|qbininrginformÎationf*roms1eve ral leGs,^witUhdi erentpurpGoqs1es.K First,^suUbs#idiary leGsmÎayb#ereqadinf*romtUhemÎainsource leinaways#imilartrotUheway#include3 leGsarehandleGdbyaC compile r.IntUhecas1eofCWEBVXhÎoweve r, tUhemÎainpurpGoqs1ei#susuallynottroshareinformÎationamonrgs1eve ralsourceGs,burtme relytoallowbreqakinguplargesource leGsintomoreeqas#ilymÎanageableparts.qdSecondtUhe rei#stUhechanrgeg lemechani#smgalreqadymentioneGdgabove,Зwhichgs1e rvesgtroinstallsystUemdTep#endentgpatcheGstroamÎastUe rsource,UUallowinrgtUhatmÎastUe rtroremainf*reeofsystUemdTep#endencieGs. p荑 WhenalineoftUheform`@ih leUUnÎameiA#'app#eqarsinaCWEBsource le,ACWEBwillreadintUheindicatUeGd leQattUhatpGoint,andcontinUuereqadinrgatthenextlinewhenitreqacheGstUheendoftUhesuUbqs#idiary le.ӺTheh leUUnÎamei59mÎayˎeGitUhe rb#edTelimitUedbywhitUespace,orb#eencloqs1edindouUble-quotUecharacte rsˎ(burtnotinanrglebrackets).mSource leGsmÎayb#eneGstUedintUhi#swayuptro10levelsdTeep.mNotUhinrginthepr*intUeGdCWEBdoGcurment%willindicatUetUheswitchf*romonesource letroanotUhe r,/tnorwilltUhe reb#eanye ectontUheC , le(s)wr*ittUensbyCTANGLE) ƫ,excepttUhat#lin9e#rdirectiveGswillofcours1ealwayspGointtrotUheprop#e rpGointofor*iginforUUeqachpieceofcoGdTewr*ittUentrosuch leGs. LikeforheqadTe r leGs, tUhe rei#sawaytroindicatUetUhatifa leincludTeGdby`@i b'i#snotfourndintUhecurrentdirectrory*,۟analtUe r#nÎativeplacecanb#etr*ieGd;{urnlikeheqadTe r leGshÎoweve rtUhe rei#srelativelylittUleneeGdtrous1etUhi#sT8facility*,TqurnleGsqsonehas leGstUhatareus1efultroincludTeidenticallyinmoretUhanonepro8ject.qhAtmoqstonealrtUe r#nÎative[placetos1eqarchcanb#egiven,anditi#sspeci eGdbyapre xtrobeapplieGdtrotUhe lenÎame,intUhesamewayasforheqadTe r leGs.+Thi#spre xmÎayeitUhe rb#ecompiledintrotUheCWEBprogramsbys1ettinrgtUhepreproGcesqsorsym|qbGolGCWEBINPUTS;equalGtrotUhatstr*ingwhencompilingcommon.c1(anÎalogouslytoCWEBHEADERS=),Jioritcanb#e~4speci eGdatrurntimebys1ettinrgtUheenvironmentvqar*iableCWEBINPUTS8~;whenbGotUhmetUhÎoGdsareus1ed,ltUhelattUe rUUtakeGsprecedTence. The chanrge le,ifpreGs1ent,contains as1equenceof\chanrgeGs",eqachofwhichsp#eci eGstUhereplacementof]oneormorelineGsf*romtUhemÎaininpurtstreqambyanotUhe rs1etoflineGs.EEachchanrgehastUheform`@xhor*iginÎalUUlineGsiFy@yUKhreplacementUUlineGsi%@z,,',8whe re˥eqachoftUhecoGdTes`@x b',8`@y',and˥`@z'oGccupiesalinebyits1elf.cThe++hor*iginÎalUUlineGsiIi#s++anon-emptysetoflineGstUhatshÎouldmatch++exactUlywithsomes1equenceoflineGsinFtUhemÎaininpurtstreqam(exceptforthef#actthattrailinrgwhitUespaceonanylinei#signoreGd).lF*urtUhe rmore,di e rentpchanrgeGsshÎoulda ectnon-ove rlappinrgs1etsoflineGs,wlandtUheGirordTe rintUhechanrge leshÎouldb#etUhesameastUhatoftUhepartsoftUhemÎaininpurtstreqamtUhattUheyreplace.+OF*oreqachchanrgeinsucceGsqs#ion,3as1equenceof̆lineGsmÎatchinrghor*iginÎalUUlineGsiHGIi#ss1eqarcheGdfor,andreplaceGdbytUhecorreGspondinrğhreplacementUUlinesiX«;!likefor`@i b' leins1e rtions,tUhereGsulrtingstreqamoflineGswillb#eprocesqs1edintUheusualwayasifitconstiturtUeGdas#inrgle\+CWEB>source\+ le.HThe\mÎaininputstreqam"refe rreGdtohe rei#stUhereGsulrtof(recurs#ively)ins1e rtinrganyauxiliary^ leGsindicatUedby`@i b'lineGsintrotUhemÎainCWEBsource le.9IttUhe reforemÎakeGsnos1ense^trosp#ecify`@i b'in_tUhehor*iginÎalUUlineGsiFH,nori#s`@i b'alloweGdintUhehreplacementUUlineGsiY:itshÎoulds#implynotoGccuranywhe reintUhechanrge le.fOntUheotUhe rhanditi#slegitimÎatUefortUhehor*iginÎalUUlineGsiJQtromÎatchas1equenceoflineGscominrgUUf*rommoretUhanonephys#icalsource le. Theuf#acttUhatinpurti#stUempGorar*ilyswitcheGdtrotUhechanrge lei#snotentirelytransparenttrotUheCWEBdoGcurment,as|itwasintUhecas1eif`@i b' leGs:CWEAVE(CԫwillmÎarkallsectionstUhatwe remoGdi ed|urndTe rcontrolof0tUhechanrge le,gbyattachinrganastUe r*i#sktotUheGirs1ectionnUurm|qb#e r,gandtroallrefe renceGstotUhatnurm|qb#e r.(IfqsomechanrgeGsshÎouldaddorremoveentires1ectionsintUhemiddleoftUheCWEB>source,@xwhichi#salloweGdڠn썫22SUBSIDIARJYXINPUTFILESANDCHANGEFILES>CWEBxEMANUALn@PalrtUhÎoughy[notencourageGd,]thenthes1ectionnUurm|qb#e r*ingy[willbealrtUe reGd,]buty[s1ectionsforwhichtUhi#sistUheonly chanrge+willnotb#e aggeGdwitUhanastUe r*isk.)cIfoneisonlyintUe reGsted+ins1ectionstUhataremoGdi ed,3tUhen+iti#sevenKpGoqss#ibletroreGstr*ictprintinrgtoonlytUhÎoqs1esections, byincludinrgtUheTU>'ExXcommÎand`\changesonly?D'intUheUUtUextinlim|qbGo,prefe rablybymeqansoftUhechanrge le. % In{ordTe rtrof#acilitatUeecientimplementationoftUhechanrge lemechani#sm,%anadditionÎalconstrainti#splaceGd.ontUhechanrgeGs:^ onceanexactmÎatchofalineintUhemÎaininpurtstreqamwitUhthe rst.lineofachanrgei#sKfournd,MtUheremÎaininrglineGsoftUhechanrge(uptotUhe`@y b')shÎouldalsomatch.nAnyemptylineGsimmeGdiatUelyfollowinrg<`@x b'arenotus1eGdformÎatchinrg(andareinf#actcompletUelyignoreGd)sotUhe rst'ExXpartofs1ections(aftUe rall,]'ExXparti#sempty)byplacinrgaTU>'ExXcommentintUhemÎaininpurt,]tUhats1e rveGsme relyasatargetforreplacementbytUhechanrge le. [AlltUextintUhechanrge letUhati#snotpartofachanrgei#signoreGd,excepttUhatthe reshÎouldb#enolineGsstartinrgwitUh`@i b',+`@y',or`@z';VtUhi#stUextcanbeus1eGdforinstancetroexplaintUhepurpGoqs1eofthechanrgetotUhep#e rsoninstallinrgtUheprogramonanewsystUem,ratUhe rtUhantrotUheordinÎaryUUreqadTe roftUheprogram. 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OneshÎouldnotgetcarr*ieGdawaybytUheb#ene tsofchanrge leGstUhÎough:#theyprovidTeonlyaratUhe rcrudTemechani#sm(duetrotUhein exiblemÎatchinrgruleGs),andiftUhe rearemÎanychanrgeGs,tUheywillb#ecomediculrttomÎaintain7whentUhemÎastUe r leevolveGs.DPortabilityi#sstillb#eGstobtaineGdbylimitinrgsystUemdTep#endent7feqatureGsasdmUuchaspGoqss#ible, andifinevitable, con ninrgtUhemtrosomewelldTe neGdpartoftUheprogram.SwIfoneshÎouldwi#shɖtrocreqatUevqar*iantsofaprogramtUhatinvolveɖs#igni cantchanrgeGs,tUhenɖwr*itingɖextUens#ivechanrge leGsi#sprobably)nottUheb#eGstwaytrogo.cDThi#smetUhÎoGdcouldleqadtroaformof\r*igormorti#s"fortUheor*iginÎalve rs#ionoftUheprogram,caus1eGdbyfeqartUhatanyalrtUe rationscouldupqs1etoneoftUhechanrge leGs,eventr*ivialchanrgeGstUhatonlyinvolvetUhecommentary*,orevenjusttUhelayourtoftUhesource le.Ab#ettUe rapproachwouldb#etrocollectrourtineGsofgene ralurtilityasmUuchaspGoqss#ibleintros1eparatUecompilationurnitsus1eGdbyallvqar*iants,eandtro|EcomplementtUheGs1ewitUhcompletUelyindTep#endent|EcompilationurnitstodTe netUhesp#eci cbehaviour|Eofeqachof tUhevqar*iants.B Iti#sce rtainlypGointUlesqs trous1eachanrge leforsuchtUhinrgsasbug xeGsorfurthe rdTevelopmentof[aprogram;^tUhewhÎoleidTeqai#sthatsuchmoGdi cationscanb#emÎadTeintUhemÎastUe r lewhiletUhechanrge leGsforUUvqar*ioussystUemsneeGdlittUleornoadjustment. 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AIgroupIoftUhreecoGdTesIs1e rvestroincludTeadditionÎalentr*iesintUheindTex,K}amidsttUhÎoqs1egene ratUeGdaurtomÎati-callyYbyCWEAVE&nforidTenti e rs.~lItmÎayb#eus1efulforinstancetromÎaintainrefe renceGstroconceptslike`systUemdTep#endencieGs',x orqtroalle rrormeGsqsagesqtUhatcanb#egene ratUeGd.ThetUhreecoGdTesqare`@^ b',x `@.',andq`@?';~tUheydi e r onlyintUhewaytUheindTexentrywillb#etyp#eGs1et.6Ineqachcas1etUheindTexentryi#sspeci eGdasacontroltUexttUe rminÎateGdXby`@> b';controlcodTeandcontroltUextwillb#eremoveGdbyCWEAVE"᮫,burttUhecontroltUextwillapp#eqarin tUheindTex,6followeGdbytUhes1ectionnUurm|qb#e r(s)whe retUhecontrolcoGdTeoccurred.GF*or`@^ b',`@.',6and`@?',tUheindTexentrywillb#es1etreGspectivelyinromÎantyp#e, ;intyp#ewr*itUe rtyp#e, ;andasargurmenttrotUhecontrols1equencev`\9 b'(whichi#surndTe neGdintUhestandrardformÎat,>butwhichtUheprogramme rmÎaydTe neinlim|qbGo).The7 rstpGoqss#ibilityismoqstsuitUeGdforgene ralconcepts,10tUhes1econdforstr*inrgstUhatoGccurintUheprogram,and?#tUhetUhirdforanyfurtUhe rsp#ecialpurpGoqs1eonemÎaytUhinkof.jaTheGs1econtrolcodTescanb#epurteitUhe rintheTU>'ExXpartofas1ectionorwitUhinCXcoGdTe;0thee ectwillb#ethesame,burttUhi#sallowstUheprogramme rtroputtUhewcontrolcoGdTeinsuchaplacetUhatiti#smoqstlikelytroremÎainintUher*ightplaceincas1etUhes1ectionshÎouldb#ereorganis1eGdandpoqss#iblysuUbGdividTed.kLikeforrefe rencestroidTenti e rs,onecanmÎakeanindTexrefe renceurndTe rlineGdUUbypre xinrgtUhecorreGspondinrgcontrolcodTewitUh`@! b'. 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The remi#sanotUhe rus1eof`@+ b',swhichdo#eGsnotcaus1eanybreqakstrob#ecancelleGd,sbutwhe reontUhecontrarytUheףpurpGoqs1ei#sinse rtwhitUespace.GItapplieGswhenalonrgstr*ingconstanti#sneeGdTed,forףwhichtUhestr*inrg-breqakfeqature-i#sus1eGd:13asequenceofstr*inrgsseparatUeGdbywhitespaceonlywillb#econcatenÎateGd-bytUhecompile rintroa2s#inrglestr*ing.fEAltUhÎoughCTANGLE+willcorrectlyins1e rtaspaceb#etween2anytwocons1ecurtivestr*inrgs,9CWEAVE(guidTeGdbysyntaxratUhe rtUhanbylexicalstructure)wills#implyjuxtapGoqs1etUhem;nbyins1e rtinrg`@+ b'b#etweentUhestr*inrgs,oneguarantUeeGstUhatintUhepr*intUeGddocurmenttUhe rewilleGitUhe rb#eahÎor*izontals1eparationor(iftUheRconstituentstr*inrgstUhems1elveGsarealreqadylonrg)alinebreqak.[IncidTentally*,iftUheproblemofbreqakinrgastr*inrg&i#sintUhesource lerathe rthaninthepr*intUeGdourtʪput,bone&canus1etUhetraditionÎalsolurtionofaneGsTcap#ednewlineT\witUhinthestr*inrg;TCWEAVE&awilltreqatthi#sasifthepartsofthestr*inrgwe reontUhesamesourceline.qtIfonewshÎouldcreqatUeastr*inrgintUhi#swaytUhatdo#eGsno tonasinrglelineofoutʪput,Wabreqakwillb#eintroGducedaurtomÎatically[atasomepGoint,whichwillb#etyp#eGs1etasifastr*inrg-breqakwasus1eGd.nInve rylonrgstr*ingshÎoweve riti#sbettUe rtrowr*itestr*inrg-breqaksexplicitUly;aforstr*inrgsbrokenonlybyeGsTcap#ednewlines,4tUhesamelenrgtUhUUlimithÎoldsasformoGdulenameGs(1000charactUe rs).Coi>des;forspecialitemsin,kCcode:~`Ka@p Q',@`Ka@v',`Ka@t',`Ka@&',`Ka@=',`Ka@'' Contraryj8troTU>'ExXtUext,oqpieceGsofC VcoGdTearebrokenupintrotokensbybGotUhCTANGLE++sandCWEAVE",QstroreGdintUe r#nÎallyandourtʪputatsomelatUe rtime>aftUe rhavinrg>undTergone>someproGcesqs#inrg.AjThismÎakeGsitpotUentiallydiculrttoputsometUhingintoC 6coGdTetUhatCWEB>i#snotprepareGdtrohandle.FSinceCei#samUuchmoreregularlanrguagetUhatTU>'ExX,oGccas#ionswhe reonewouldneeGdtrodosuchatUhinrgshÎouldb#equitUerare, yetsomeeGsTcap#emechani#smshaveb#eenprovidTeGd,whichUUwetreqatintUhi#ssubqs1ection. 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