Another Simple Program: Adding Two Integers

AnotherSimpleProgram:AddingTwoIntegers


•  Thisprogramusestheinputstreamobjectstd::cinandthestreamextrac<onoperator,>>,toobtaintwointegerstypedbyauseratthekeyboard,computesthesumofthesevaluesandoutputstheresultusingstd::cout.

Note:‘<<‘iscalled‘inser<onoperator’


•  Variabledeclara0on:

•  number1,number2,sumarethenamesofvariables•  Avariableisaloca<oninthecomputer’smemorywhereavalue

canbestoredforusebyaprogram.•  Thesedeclara<onsspecifythatthevariablesnumber1,number2,

andsumaredataoftypeint,meaningthatthesevariableswillholdintegervalues,i.e.,wholenumberssuchas7,–11,0and31,914.

•  Allvariablesmustbedeclaredwithanameandadatatypebeforetheycanbeusedinaprogram.

•  Severalvariablesofthesametypemaybedeclaredinonedeclara<onorinmul<pledeclara<ons.Wecouldhavedeclaredallthreevariablesinonedeclara<onbyusingacomma-separatedlistasfollows:int number1, number2, sum;!


•  Variable’sname– Aseriesofcharactersconsis<ngofleQers,digitsandunderscores(_).

– DoesNOTbeginwithanumber.– C++iscasesensi<vei.e.,uppercaseandlowercaseleQersaredifferent,soa1andA1representdifferentvariables.

– MustNOTbeaspecialcharactere.g.,&,%,$,… – MustNOTbeakeyword.(Whatisakeyword?)


•  Variable’stypes–  We’llsoondiscussthetypefloatforspecifying

decimalnumbers,andthetypecharforspecifyingcharacterdata.•  Decimalnumbersarenumberswithdecimalpoints,

suchas3.4,0.0and–11.19.•  Acharvariablemayholdonlyasinglelowercase

leQer,asingleuppercaseleQer,asingledigitorasinglespecialcharacter(e.g.,$or*).

–  Typessuchasint,float,andchararecalledfundamentaltypes.

–  Fundamental-typenamesarekeywords.


•  PlacementofVariableDeclara0ons– Declara<onsofvariablescanbeplacedalmostanywhereinaprogram,buttheymustappearbeforetheircorrespondingvariablesareusedintheprogram.


•  ObtainingtheFirstValuefromtheUser

–  displaysEnterfirstinteger:followedbyaspace.Thismessageiscalledapromptbecauseitdirectstheusertotakeaspecificac<on.

–  usesthestandardinputstreamobjectcin(ofnamespacestd)andthestreamextrac<onoperator,>>,toobtainavaluefromthekeyboard.

–  Usingthestreamextrac<onoperatorwithstd::cintakescharacterinputfromthestandardinputstream,whichisusuallythekeyboard.


•  ObtainingtheSecondValuefromtheUser


•  Calcula0ngtheSumoftheValuesInputbytheUser

–  Thisassignmentstatementaddsthevaluesofvariablesnumber1andnumber2andassignstheresulttovariablesumusingtheassignmentoperator=


•  DisplayingtheResult

– displaysthecharacterstringSumisfollowedbythenumericalvalueofvariablesumfollowedbystd::endl—aso-calledstreammanipulator.

– Thenameendlisanabbrevia<onfor“endline”andbelongstonamespacestd.Thestd::endlstreammanipulatoroutputsanewline.

MemoryConcepts

•  Variablenamessuchasnumber1,number2andsumactuallycorrespondtoloca<onsinthecomputer’smemory.Everyvariablehasaname,atype,asizeandavalue.

Arithme<c

•  C++providesthemodulusoperator,%,thatyieldstheremainderamerintegerdivision.Themodulusoperatorcanbeusedonlywithintegeroperands.Theexpressionx%yyieldstheremainderamerxisdividedbyy.Thus,7%4yields3and17%5yields2.

Arithme<c•  Examples,

Arithme<c•  RulesofOperatorPrecedence

C++appliestheoperatorsinarithme<cexpressionsinapreciseorderdeterminedbytheserulesofoperatorprecedence,whicharegenerallythesameasthoseinalgebra:1.  Operatorsinexpressionscontainedwithinpairsof

parenthesesareevaluatedfirst.Parenthesesaresaidtobeatthe“highestlevelofprecedence.”Incasesofnested,orembedded,parentheses,suchas(a*(b+c)),theoperatorsintheinnermostpairofparenthesesareappliedfirst.

2.   Mul0plica0on,division,andmodulusopera<onsareappliednext.Ifanexpressioncontainsseveralmul<plica<on,divisionandmodulusopera<ons,operatorsareappliedfromlemtoright.

3.   Addi0onandsubtrac0onopera<onsareappliedlast.Ifanexpressioncontainsseveraladdi<onandsubtrac<onopera<ons,operatorsareappliedfromlemtoright.

Arithme<c•  Examples

1:2+(2-2)*(2+2)/2=?2:3+3-3*(3/3)=?3:(4+4–4*4)/((4+4)*-1)=?4:(22%4–1)/2+1/2=?

ModifytheProgram

•  Writeaprogramthattakesthreeintegersfromtheuserandoutputsthefollowingopera<on:

Decisionmaking(EqualityandRela<onalOperators)

•  Theifstatementallowsaprogramtotakealterna<veac<onbasedonwhetheracondi<onistrueorfalse.–  Ifthecondi<onistrue,thestatementinthebodyoftheifstatementisexecuted.Ifthecondi<onisfalse,thebodystatementisnotexecuted.

– Condi<onsinifstatementscanbeformedbyusingtheequalityoperatorsandrela<onaloperators.


•  Ifstatement if(condi<on){ //dosomething… }



•  Let’swriteaprogramthatcomparestwointegers!


using namesapce std!isadirec<vethatenablesaprogramtouseallnamesinanystandardC++headersuchas<iostream>

LabAssignment#1

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Another Simple Program: Adding Two Integers