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AFirstBookofANSIC

FourthEditionChapter3ProcessingandInteractiveInput1AFirstBookofANSIC,FourthEditionObjectivesAssignmentMathematicalLibraryFunctionsInteractiveInputFormattedOutput2AFirstBookofANSIC,FourthEditionObjectives(continued)SymbolicConstantsCaseStudy:InteractiveInputCommonProgrammingandCompilerErrors3AFirstBookofANSIC,FourthEditionAssignmentThegeneralsyntaxforanassignmentstatementis variable=operand;Theoperandtotherightoftheassignmentoperator(=)canbeaconstant,avariable,oranexpressionTheequalsigninCdoesnothavethesamemeaningasanequalsigninalgebralength=25;isread“lengthisassignedthevalue25”Subsequentassignmentstatementscanbeusedtochangethevalueassignedtoavariablelength=3.7;length=6.28;4AFirstBookofANSIC,FourthEditionAssignment(continued)TheoperandtotherightoftheequalsigninanassignmentstatementcanbeavariableoranyvalidCexpression sum=3+7; product=.05*14.6;Thevalueoftheexpressiontotherightof=iscomputedfirstandthenthecalculatedvalueisstoredinthevariabletotheleftof=Variablesusedintheexpressiontotherightofthe=mustbeinitializediftheresultistomakesenseamount+1892=1000+10*5isinvalid!5AFirstBookofANSIC,FourthEditionAssignment(continued)Ifwidthwasnotinitialized,thecomputerusesthevaluethathappenstooccupythatmemoryspacepreviously(compilerwouldprobablyissueawarning)6AFirstBookofANSIC,FourthEditionAssignment(continued)=hasthelowestprecedenceofallthebinaryandunaryarithmeticoperatorsintroducedinSection2.4Multipleassignmentsarepossibleinthesamestatement a=b=c=25;All=operatorshavethesameprecedenceOperatorhasright-to-leftassociativityc=25;b=c;a=b;7AFirstBookofANSIC,FourthEditionImplicitTypeConversionsDatatypeconversionstakeplaceacrossassignmentoperatorsdoubleresult;result=4;//integer4isconvertedto4.0Theautomaticconversionacrossanassignmentoperatoriscalledanimplicittypeconversionintanswer;answer=2.764;//2.764isconvertedto2Heretheimplicitconversionisfromahigherprecisiontoalowerprecisiondatatype;thecompilerwillissueawarning8AFirstBookofANSIC,FourthEditionExplicitTypeConversions(Casts)Theoperatorusedtoforcetheconversionofavaluetoanothertypeisthecastoperator (dataType)expressionwheredataType

isthedesireddatatypeoftheexpressionfollowingthecastExample:Ifsumisdeclaredasdoublesum;,(int)sumistheintegervaluedeterminedbytruncatingsum’sfractionalpart9AFirstBookofANSIC,FourthEditionAssignmentVariationssum=sum+10isnotanequation—itisanexpressionthatisevaluatedintwomajorsteps10AFirstBookofANSIC,FourthEditionAssignmentVariations(continued)11AFirstBookofANSIC,FourthEditionAssignmentVariations(continued)12AFirstBookofANSIC,FourthEditionAssignmentVariations(continued)Assignmentexpressionslikesum=sum+25canbewrittenusingthefollowingoperators:+=-=*=/=%=sum=sum+10canbewrittenassum+=10price*=rateisequivalenttoprice=price*rateprice*=rate+1isequivalenttoprice=price*(rate+1)13AFirstBookofANSIC,FourthEditionAccumulatingThefirststatementinitializessumto0ThisremovesanypreviouslystoredvalueinsumthatwouldinvalidatethefinaltotalApreviouslystorednumber,ifithasnotbeeninitializedtoaspecificandknownvalue,isfrequentlycalledagarbagevalue14AFirstBookofANSIC,FourthEditionAccumulating(continued)15AFirstBookofANSIC,FourthEditionAccumulating(continued)16AFirstBookofANSIC,FourthEditionCountingAcountingstatementisverysimilartotheaccumulatingstatement variable=variable+fixedNumber;Examples:i=i+1;andm=m+2;Incrementoperator(++):variable=variable+1canbereplacedbyvariable++or++variable17AFirstBookofANSIC,FourthEditionCounting(continued)18AFirstBookofANSIC,FourthEditionCounting(continued)19AFirstBookofANSIC,FourthEditionCounting(continued)Whenthe++operatorappearsbeforeavariable,itiscalledaprefixincrementoperator;whenitappearsafteravariable,itiscalledpostfixincrementoperatork=++n;isequivalentton=n+1;//incrementnfirstk=n;//assignn'svaluetokk=n++;isequivalenttok=n;//assignn'svaluetokn=n+1;//andthenincrementn20AFirstBookofANSIC,FourthEditionCounting(continued)Prefixdecrementoperator:theexpressionk=--nfirstdecrementsthevalueofnby1beforeassigningthevalueofntokPostfixdecrementoperator:theexpressionk=n--firstassignsthecurrentvalueofntonandthenreducesthevalueofnby121AFirstBookofANSIC,FourthEditionCounting(continued)22AFirstBookofANSIC,FourthEditionMathematicalLibraryFunctions23AFirstBookofANSIC,FourthEditionMathematicalLibraryFunctions(continued)Theargumenttosqrtmustbefloating-pointvalue;passinganintegervalueresultsinacompilererrorReturnvalueisdouble-precisionMustinclude#include<math.h>24AFirstBookofANSIC,FourthEditionMathematicalLibraryFunctions(continued)25AFirstBookofANSIC,FourthEditionMathematicalLibraryFunctions(continued)26AFirstBookofANSIC,FourthEditionMathematicalLibraryFunctions(continued)Argumentneednotbeasingleconstant27AFirstBookofANSIC,FourthEditionMathematicalLibraryFunctions(continued)Thestep-by-stepevaluationoftheexpression 3.0*sqrt(5*33-13.91)/5 is(seenextslide)28AFirstBookofANSIC,FourthEditionMathematicalLibraryFunctions(continued)29AFirstBookofANSIC,FourthEditionMathematicalLibraryFunctions(continued)Determinethetimeittakesaballtohitthegroundafterithasbeendroppedfroman800-foottowertime=sqrt(2*distance/g),whereg=32.2ft/sec230AFirstBookofANSIC,FourthEditionMathematicalLibraryFunctions(continued)31AFirstBookofANSIC,FourthEditionInteractiveInput32AFirstBookofANSIC,FourthEditionInteractiveInput(continued)Thisprogrammustberewrittentomultiplydifferentnumbersscanf()isusedtoenterdataintoaprogramwhileitisexecuting;thevalueisstoredinavariableItrequiresacontrolstringasthefirstargumentinsidethefunctionnameparentheses33AFirstBookofANSIC,FourthEditionInteractiveInput(continued)Thecontrolstringpassedtoscanf()typicallyconsistsofconversioncontrolsequencesonlyscanf()requiresthatalistofvariableaddressesfollowthecontrolstringscanf("%d",&num1);34AFirstBookofANSIC,FourthEditionInteractiveInput(continued)35AFirstBookofANSIC,FourthEditionInteractiveInput(continued)ThisstatementproducesapromptAddressoperator(&)36AFirstBookofANSIC,FourthEditionInteractiveInput(continued)scanf()canbeusedtoentermanyvaluesscanf("%f%f",&num1,&num2);//"%f%f"isthesameAspacecanaffectwhatthevaluebeingenterediswhenscanf()isexpectingacharacterdatatypescanf("%c%c%c",&ch1,&ch2,&ch3);storesthenextthreecharacterstypedinthevariablesch1,ch2,andch3;ifyoutypexyz,thenxisstoredinch1,ablankisstoredinch2,andyisstoredinch3scanf("%c%c%c",&ch1,&ch2,&ch3);causesscanf()tolookforthreecharacters,eachcharacterseparatedbyexactlyonespace37AFirstBookofANSIC,FourthEditionInteractiveInput(continued)Inprintingadouble-precisionnumberusingprintf(),theconversioncontrolsequenceforasingle-precisionvariable,%f,canbeusedWhenusingscanf(),ifadouble-precisionnumberistobeentered,youmustusethe%lfconversioncontrolsequencescanf()doesnottestthedatatypeofthevaluesbeingenteredInscanf("%d%f",&num1,&num2),ifuserenters22.87,22isstoredinnum1and.87innum238AFirstBookofANSIC,FourthEditionCaution:ThePhantomNewlineCharacter39AFirstBookofANSIC,FourthEditionCaution:ThePhantomNewlineCharacter(continued)ThefollowingisasamplerunforProgram3.10:Typeinacharacter:mThekeystrokejustacceptedis109Typeinanothercharacter:Thekeystrokejustacceptedis1040AFirstBookofANSIC,FourthEditionCaution:ThePhantomNewlineCharacter(continued)41AFirstBookofANSIC,FourthEditionCaution:ThePhantomNewlineCharacter(continued)42AFirstBookofANSIC,FourthEditionAFirstLookatUser-InputValidation43AFirstBookofANSIC,FourthEditionAFirstLookatUser-InputValidation(continued)Aswritten,Program3.12isnotrobustTheproblembecomesevidentwhenauserentersanon-integervalueEnterthreeintegernumbers:1020.6820Theaverageof10,20,and-858993460is-286331143.333333Handlinginvaliddatainputiscalleduser-inputvalidationValidatingtheentereddataeitherduringorimmediatelyafterthedatahavebeenenteredProvidingtheuserwithawayofreenteringanyinvaliddata44AFirstBookofANSIC,FourthEditionFormattedOutput618124---148Outputisnotaligned45AFirstBookofANSIC,FourthEditionFormattedOutput(continued)618124---148Fieldwidthspecifier46AFirstBookofANSIC,FourthEditionFormattedOutput(continued)47AFirstBookofANSIC,FourthEditionFormatModifiersLeftjustification:printf("%-10d",59);producesthedisplay59٨٨٨٨٨٨٨٨Explicitsigndisplay:printf("%+10d",59);producesthedisplay٨٨٨٨٨٨٨+59Formatmodifiersmaybecombined%-+10dwouldcauseanintegernumbertobothdisplayitssignandbeleft-justifiedinafieldwidthof10spacesTheorderoftheformatmodifiersisnotcritical%+-10disthesame48AFirstBookofANSIC,FourthEditionOtherNumberBases[Optional]Thedecimal(base10)valueof15is15.Theoctal(base8)valueof15is17.Thehexadecimal(base16)valueof15isf.49AFirstBookofANSIC,FourthEditionOtherNumberBases(continued)50AFirstBookofANSIC,FourthEditionOtherNumberBases(continued)Thedecimalvalueoftheletterais97.Theoctalvalueoftheletterais141.Thehexvalueoftheletterais61.51AFirstBookofANSIC,FourthEditionOtherNumberBases(continued)52AFirstBookofANSIC,FourthEditionSymbolicConstantsLiteraldatareferstoanydatawithinaprogramthatexplicitlyidentifiesitselfLiteralvaluesthatappearmanytimesinthesameprogramarecalledmagicnumbersCallowsyoutodefinethevalueoncebyequatingthenumbertoasymbolicname#defineSALESTAX0.05#definePI3.1416Alsocalledsymbolicconstantsandnamedconstants53AFirstBookofANSIC,FourthEditionSymbolicConstants(continued)#signisasignaltoaCpreprocessor54AFirstBookofANSIC,FourthEditionCaseStudy:InteractiveInput55AFirstBookofANSIC,FourthEditionCaseStudy:InteractiveInput(continued)56AFirstBookofANSIC,FourthEditionCommonProgrammingErrorsForgettingtoassigninitialvaluestoallvariablesbeforethevariablesareusedinanexpressionCallingsqrt()withanintegerargumentForgettingtousetheaddressoperator,&,infrontofvariablenamesinascanf()functioncallNotincludingthecorrectcontrolsequencesinscanf()functioncallsforthedatavaluesthatmustbeenteredIncludingamessagewithinthecontrolstringpassedtoscanf()57AFirstBookofANSIC,FourthEditionCommonProgrammingErrors(continued)Terminatinga#definecommandtothepreprocessorwithasemicolonPlacinganequalsignina#definecommandwhenequatingasymbolicconstanttoavalueUsingtheincrementanddecrementoperatorswithvariablesthatappearmorethanonceinthesameexpressionBeingunwillingtotestaprogramindepth58AFirstBookofANSIC,FourthEditionCommonCompilerErrors59AFirstBookofANSIC,FourthEditionCommonCompilerErrors(continued)60AFirstBookofANSIC,FourthEditionSummary