高级编程语言课件

高级编程语言Compilers（编译器）Compiler

Aprogramthattranslatesahigh-levellanguageprogramintomachinecodeHigh-levellanguagesprovidearichersetofinstructionsthatmakestheprogrammer’slifeeveneasierthanworkinginassemblylanguage.Aslongasacompilerforthehigh-levellanguageiswrittenforaspecificcomputer,programswritteninthehigh-levellanguagewillrunonthatcomputer.Wesaythatahigh-levellanguageismachine-independent.Machinelanguageandassemblylanguagearemachine-dependent.Compilers（编译过程）Figure8.1CompilationprocessInterpreters（解释器）InterpreterAtranslatingprogramthattranslatesandexecutesthestatementsinsequenceAnassemblerorcompilerproducesmachinecodeasoutputandthatoutputisthenexecutedinaseparatestepAninterpretertranslatesastatementandthenimmediatelyexecutesthestatementInterpreterscanbeviewedassimulators

JavaIntroducedin1996Portability(i.e.machine-independence)wasofprimaryimportanceJavaiscompiledintoastandardizedmachinelanguagecalledBytecodeAsoftwareinterpretercalledtheJVM(JavaVirtualMachine)takestheBytecodeprogramandexecutesitProgrammingLanguageParadigmsFigure8.2

PortabilityprovidedbystandardizedlanguagesversusinterpretationbyBytecodeProgrammingLanguageParadigmsFigure8.2

PortabilityprovidedbystandardizedlanguagesversusinterpretationbyBytecodeFourProgrammingLanguageParadigmsImperativeorproceduralmodelFORTRAN,COBOL,BASIC,C,Pascal,

Ada,andC++FunctionalmodelLISP,Scheme(aderivativeofLISP),andMLLogicprogrammingmodelPROLOGObject-orientedmodelSIMULAandSmalltalkC++isasanimperativelanguagewithsomeobject-orientedfeaturesJavaisanobject-orientedlanguagewithsomeimperativefeaturesFunctionalityofImperativeLanguagesImperativelanguagestypicallyusethefollowingtypesofinstructions:SequencingExecutestatementsinsequenceuntilaninstructionisencounteredthatchangesthissequencing

SelectionDecidewhichactiontotakeIteration(looping)Repeatanaction BothselectionanditerationrequiretheuseofaBooleanexpressionAnIntroductiontotheImperativeFeaturesofJava

Many,butnotall,high-levellanguageshaveimperativefeatures.Javaisobject-orientedalso,butwewilldelaydiscussingthatpartofthelanguageinitially.First,wewillconcentrateontheimperativefeaturesthatJavashareswithC++.Almostalloftheearlyhigh-levellanguageswereimperativelanguages.StructureofJavaProgram//Prologuecomment–whattheprogramdoes//WrittenbyJ.Q.Programmer,10/20/01publicclassName{//classnamestartswithacapitalletterpublicstaticvoidmain(String[]args){

statement1;//Semicolonseparatesstatements

statement2;//Programbody

….

}//endofmethodmain'sdefinition}//endoftheclassdefinitionVariableVariableAlocationinmemorythatcontainsadatavalueandisreferencedbyanidentifier

Inassemblylanguage,avariablecorrespondstoadatamemorylocationthatistaggedwithalabel.Thelabelistheidentifier.Forexample,count.data5Inourassemblylanguage,wehadnorulesforformingidentifiers,butinmosthighlevellanguages,onlycertaincombinationsofcharacterscanbeused.

JavaRulesforCreatingIdentifiersUseanycombinationofdigits,letters,and_(theunderscoresymbol),butdon'tstartwithadigit.Javaisacase-sensitivelanguagei.e.eachofthefollowingisdifferent:

this THIS thIS

ThIs...Anidentifiercanbeofanylength.Aprogrammer-chosenidentifiermaynotbeareservedwordi.e.awordintheJavalanguagesuchasclass,public,int,etc.StrongTypingStrongtyping

TherequirementthatonlyavalueofthepropertypecanbestoredintoavariableDatatypeAdescriptionofthesetofvaluesandthebasicsetofoperationsthatcanbeappliedtovaluesofthetypeJavaisstronglytyped.PrimitiveDataTypesinJavaandManyOtherHigh-LevelProgrammingLanguagesIntegernumbersRealnumbersCharactersBooleanvaluesStringsIntegers（整型）Typicallythesearewholenumbers,theirnegatives,andzero.TherangeallowedvariesdependinguponhowmanybytesareassignedtorepresentanintegervalueSomehigh-levellanguagessupportseveralintegertypesofdifferentsizes–i.e.short,long,Operationsthatcanbeappliedtointegersarethestandardarithmetic(add,subtract,multiply,divide)andrelationaloperations(equality,lessthan,lessthanorequalto,greaterthan,greaterthanorequalto,inequality).Reals

（实数型）Thesearetypicallyfractionalnumbers.Liketheintegerdatatype,therangevariesdependingonthenumberofbytesassignedtorepresentarealnumberManyhigh-levellanguagessupporttwosizesofrealnumbersTheoperationsthatcanbeappliedtorealnumbersarethesameasthosethatcanbeappliedtointegernumbersRecall-Toacomputerscientist,2and2.0aredifferentastheyarestoreddifferently!Thefirstisaninteger;thesecondisareal.Characters（字符型）IttakesonebytetorepresentcharactersintheASCIIcharactersetTwobytesareneededtorepresentcharactersintheUnicodecharactersetOurEnglishalphabetisrepresentedinASCII,whichisasubsetofUnicodeApplyingarithmeticoperationstocharactersdoesn’tmakemuchsenseComparingcharactersdoesmakesense,sotherelationaloperatorscanbeappliedtocharactersThemeaningof“lessthan”and“greaterthan”whenappliedtocharactersis“comesbefore”and“comesafter”inthecharactersetBoolean（布尔）TheBooleandatatypeconsistsoftwovalues:trueandfalseNotallhigh-levellanguagessupporttheBooleandatatypeIfalanguagedoesnotsupportaBooleantype,thenyoucansimulateBooleanvaluesbysayingthattheBooleanvaluetrueisrepresentedby1andfalseisrepresentedby0Strings（字符串）AstringisasequenceofcharactersconsideredasonedatavalueForexample:“Thisisastring.”Contains17characters:oneuppercaseletter,12lowercaseletters,threeblanks,andaperiodNotalllanguagessupportstringsasadatatype.TheoperationsdefinedonstringsvaryfromlanguagetolanguageTheyincludeconcatenationofstrings(i.e.pastingthemtogether),comparisonofstringsintermsoflexicographicorder(i.e.alphabeticalorder)theextractingofsubstrings.DeclarationsDeclaration

Astatementthatassociatesanidentifierwithavariable,anaction,orsomeotherentitywithinthelanguagethatcanbegivenanamesothattheprogrammercanrefertothatitembynameDeclarations8-26DeclarationsinJavaEachidentifier(variable)mustbedeclared.Avariabledeclarationconsistsofadatatypefollowedbyalistofoneormoreidentifiersofthattype.Javahasmany"primitive"datatypesthatcanbeused.Oneswewilluse:

intamount;//integerdeclarationdoublesize,height;//realdeclarationcharanswer;//characterdeclarationStringName;//stringdeclaration

booleanx;Thecomputerneedstoknowthetypethatthebitsrepresent.AssignmentstatementAssignmentstatement

Anactionstatement(notadeclaration)thatsaystoevaluatetheexpressionontheright-handsideofthesymbolandstorethatvalueintothememorylocationnamedontheleft-handsideAssignmentsinJavaFormat:

Examples:

intA,B,C;//declarationscharletter=‘A’;//declarationandassignmentB=2;//assignmentsC=5;A=B+C;A=A+1;//ThisisavalidassignmentArithmeticoperations:

+,-,*,/,%variable=expression;ConstantsNamedconstant

Alocationinmemory,referencedbyanidentifier,thatcontainsadatavaluethatcannotbechangedduringtherunoftheprogram.Format:finaltypevariable=value;Examples:finaldoublePI=3.14;finalStringmyName=“Irina”;finalint

courseID=171;AssignmentStatementPage238PracticeProblemsNewNumber

andNextareintegervariablesinaJavaprogram.WriteastatementtoassignthevalueofNewNumbertoNext.WhatwillbethevalueofAverageafterthefollowingstatementsareexecuted?intTotal=277,Number=5;doubleAverage;Average=Total/Number;Next=NewNumber;Thevalueofaverageis55(integerdivision),butitisstoredasadouble–i.e.55.0InputinJavaUntilVersion5.0,Javawasnoteasytouseforkeyboardinput.Consequently,thetextintroducedaclasscalledConsole

tomakeinputsimpler.ThisisnotastandardclassintheJavalanguage.Thisclassallowspromptingandinputtooccuratthesametimeusing:

readInt,readDouble,readCharExample:doublespeed=Console.readInt("Enterthespeedinmph:");Youneedtoknowthisonlysoyoucanreadtheprogramsinthetext.WewilluseadifferentclassaswewilluseVersion5.0ofJava.PracticeProblemDeclareanintegervaluecalledquantity.

WriteastatementusingtheConsoleclassthatpromptstheusertoenteranintegervalueinapreviouslydeclaredvariablecalledquantity.intquantity;quantity=Console.readInt(“Enteranintegervalueforquantity.”);OutputinJavaFormatSystem.out.println(string);Ifthestringisempty,ablanklineisprinted.Thestringcanbecomposedusingtheconcatenationoperation,+,thatcombinesvaluesandstrings.Example:inti=10;intj=20;System.out.println("Thiswilloutputthevalueofi"+i+"andthevalueofj"+j+".");Becareful:Ifyouincludeblankswhenyousplitastringforoutput:System.out.println(“Doingthiscouldputextrablanks whereyoudon’twantthem”);println

vsprintSystem.out.println(string);printsthestringandthenissuesaCRcharacterwhichbringsthecursordowntothenextline.System.out.print(string);printsthestringandleavesthecursorattheendofthestring.Thisoneisusedwhenpromptingforinput.PracticeProblemsAprogramhascomputedavalueforthevariableaveragethatrepresentstheaveragehightemperatureinSanDiegoforthemonthofMay.Writeanappropriateoutputstatement.Whatwillappearonthescreenaftertheexecutionofthefollowingstatement?

System.out.println(“Thisis”+”goodbye”+”,Steve”);System.out.println(“Theaveragehightemperatureis”+average);Thisisgoodbye,SteveWe'llUseaClassIntroducedinJava5.0forInput–Namely,theScannerclass//Exampleofuseofscanner

importjava.util.Scanner;//inputtheScannerlibrary

publicclassExample2

{publicstaticvoidmain(String[]args)

{Scannersc=newScanner(System.in);

System.out.print("Enterthefirstnumber");

intfirst=sc.nextInt();

System.out.print("Enterthesecondnumber");

intsecond=sc.nextInt();

intsum=first+second;

System.out.println("Thesumis"+sum);

}

}

InputSummaryImporttheScannerclasswith:importjava.util.Scanner;Setuptheinputsream: Scannerstdin=newScanner(System.in);wherestdinisyourchoiceofanameforthescanner.Toinputanything,firstissueaprompt:

System.out.print("Enteranddescribeithere>");InputUsingtheScannerClassToinputaninteger:

anint=stdin.nextInt();or

int

anint=stdin.nextInt();ifthevariableanintisnotdeclared.Toinputadouble:doubleadouble=stdin.nextDouble();Toinputastring:Stringastring=stdin.nextLine();Thisstoresinastringeverythingfromthescannertotheendoftheline.HandlingcharDataScannersc=newScanner(System.in);

System.out.print("Answeryesorno:");

ans=sc.next();//readsnextstringfromthelineNowtoseewhattheansweris,youmusttestifthevariableansisayornot.Therearetwowaystodothis:if(ans.charAt(0)=='y')….orif(ans.equals("y"))…Caution-watchthetypeofquote.''denotesacharacter""denotesastringMostofmyexamplesontheslideswillusetheConsoleclassasthecodeisabitsmallerandfitsontheslidesbetter.ControlStructuresControlstructureAninstructionthatdeterminestheorderinwhichotherinstructionsinaprogramareexecutedStructuredprogrammingAprogrammingmethodologyinwhicheachlogicalunitofaprogramshouldhavejustoneentryandoneexitSequence,selectionstatements,loopingstatements,andsubprogramstatementsarecontrolstructuresBothselectionanditerationrequiretheuseofaBooleanexpressionBooleanExpressionsABooleanvariableisalocationinmemorythatcancontaineithertrueorfalse.Typically,falseisrepresentedasa0andtrueasa1oranynonzerointeger.Booleanexpression

Asequenceofidentifiers,separatedbycompatibleoperators,thatevaluatestotrueorfalseBooleanexpressioncanbeABooleanvariableAnarithmeticexpressionfollowedbyarelationaloperatorfollowedbyanarithmeticexpressionABooleanexpressionfollowedbyaBooleanoperatorfollowedbyaBooleanexpressionBooleanExpressionsArelationaloperatorbetweentwoarithmeticexpressionsisaskingiftherelationshipexistsbetweenthetwoexpressionsForexample,

xValue<yValueAnansweristrueorfalse.==!=JavaCaution:equaltois==,not=inJava.BooleanOperators

inJavaOperatorSymbol!not&&and||orBecarefultonotuseasingle&orasingle|asthosearedifferentoperations.Trueorfalsefora=2;b=3;andc=-1 1.(a<b)&&(a>c) 2.(a!=b+c)||(b-c>a) 3.!(a+b>c)||(a<=b) 4.(a-b>=c)||a>c&&b-2<cAnswers:truetruetrue4.trueSelectionStatementsTheif

statementallowstheprogramtotestthestate

oftheprogramvariablesusingaBooleanexpressionSelectionStatements

Flowofcontrolof

if-then-elsestatementSelectionStatementsSelectioninJavaFormat:if(Booleanexpression){Firstsetofstatements}else{Secondsetofstatements}if(A>B){Max=A;Min=B;}else{Max=B;Min=A;}ImportantNote:TheBooleanconditionisinparentheses,elsepartmaybeabsent,nobracketsarenecessaryifasetconsistsofonestatement.Example:SelectionStatementsinPseudocodeSameinJavaif(temp>90)

System.out.println(“Texasweather:wearshorts”);elseif(temp>70)

System.out.println(“Idealweather:shortsleevesarefine”);elseif(temp>50)

System.out.println(“Alittlechilly:wearalightjacket”);elseif(temp>32)

System.out.println(“Texasweather:wearaheavycoat”);else

System.out.println(“Stayinside”);PracticeProblemWhatistheoutputfromthefollowingsectionofcode?intnumber1=15;intnumber2=7;if(number1>=number2)System.out.println(2*number1);elseSystem.out.println(2*number2);30PracticeProblemWhatisanoutputfromthefollowingsectionofcode?

int

quotaThisMonth=7;

int

quotaLastMonth=quotaThisMonth+1;if((quotaThisMonth>quotaLastMonth)||(quotaLastMonth>=8)){System.out.println(“Yes”);

quotaLastMonth=quotaLastMonth+1;}else{System.out.println(“No”);

quotaThisMonth=quotaThisMonth+1;}YesPracticeProblemsWhatistheoutputfromthefollowingcodesegments?inta=1,b=2,c=3;if(a<b) System.out.println(“Yes”);elseSystem.out.println(“No’);System.out.println(“OK”);YesOKinta=1,b=2,c=3;if(a>b) System.out.println(“Yes”);System.out.println(“OK”);OKOtherSelectionCommands

Theif-then-elsestatementisa2-waybranchingcommand.Mostlanguagesprovideanadditionalmultiwaybranchingcommandwhichiscalledsomethingsuchasaswitchoracasestatement.Wewon’tintroducethesyntaxforthosehere.Asweknowfromtheearliercommentthatsaidwhichcommandssufficedtowriteanyalgorithm,weknowtheif-then-elseisallweneedreally.Theotherselectioncommandsjustmakesomecodingabiteasierfortheprogrammer.Supposeweencountera4-waybranchsituation:ifclassisoutput1freshman2sophomore3junior4seniorIfstatementscanbenestedinordertoprovidemultiwaybranches.if(class==1)System.out.println(“freshman”);elseif(class==2)System.out.println(“sophomore”);elseif(class==3)System.out.println(“junior”);elseif(class==4)System.out.println(“senior”);if(class==1)System.out.println(“freshman”);elseif(class==2)System.out.println(“sophomore”);elseif(class==3)System.out.println(“junior”);elseSystem.out.println(“senior”);if(class==1)System.out.println(“freshman”);if(class==2)System.out.println(“sophomore”);if(class==3)System.out.println(“junior”);if(class==4)System.out.println(“senior”);Comparethesethreepiecesofcode: Dotheyprintthesamethingforallvaluesofclass? Dotheydothesameamountofwork?if(class==1)System.out.println(“freshman”);elseif(class==2)System.out.println(“sophomore”);elseif(class==3)System.out.println(“junior”);elseif(class==4)System.out.println(“senior”);LoopingStatementsThewhilestatementisusedtorepeatacourseofactionTherearetwodistincttypesofrepetitions:Count-controlledloopsEvent-controlled

loopsCount-ControlledLoopsRepeataspecifiednumberoftimesUseofaspecialvariablecalledaloopcontrolvariableintcount=1while(count<=limit){…count=count+1;}Count-controlledloopsLoopingStatementsEvent-controlledloopsThenumberofrepetitionsiscontrolledbyaneventthatoccurswithinthebodyoftheloopitselfintn=Console.readInt(“Enteraninteger”);//initializeeventwhile(n>=0) //Testevent{… //Bodyofloopn=Console.readInt(“Enteraninteger”); //Updateevent}PracticeProblemWhatisanoutputfromthefollowingsectionofthecode?

intscores=1;while(scores<20){scores=scores+2;

System.out.println(scores);}3579111315171921PracticeProblemHowmanytimeswillthestatementwiththecommentbeexecutedinthefollowingsectionofcode?

intleft=10;

intright=20;while(left<=right){

System.out.println(left);//Thisstatementleft=left+2;}101214161820–sixtimesAdditionalLoopingCommands

Thewhileloopisknownasapretestloop.Theconditionistestedbeforetheloopisencountered.Iftheconditionisfalse,theloopisnotentered.Wesawearlierthatthewhileloopwastheonlyloopthatwasneededtowriteanyalgorithm.However,mostlanguagesprovideatleasttwootherkindsofloops:Aposttestloop(oftencalledsomethinglikearepeat-untilloop.)Aspecialcount-controlledloopwherethecounterisinitialized,tested,andincrementedautomatically(oftencalledsomethinglikeaforloop).Wewon’tshowthosehere.StoringDatainMoreComplexStructuresThanaSingleCell

Weoftenneeddatastoredinstructuresmorecomplicatedthansinglecells.Allprogramminglanguageshavesomebasicstructures.Modernprogramminglanguageshavemanytypesofcomplexstructuresthancanbeused.Forexample,ifyouwantedtomaintainalistofstudentsinaclassandtheirgrades,youmightwanttokeepsuchinformationasthefollowing:CPSC171Grades

SurnameFirstnameMiddleinitialEmailaddressLab1...LabkHomeworkTest1Test2Test3FinalCourseAlthoughmanyofthesecouldbehandledwithasinglevariableforeach,ifwehavealotofLabgrades,usingadifferentvariableforeachgradeisapain.MultipleDataThatisSimilar

Supposewehadmany,manypiecesofdatasuchasgrades,andweneeded1000ofthese.Wouldyouwanttousegrade0,grade1,grade2,...,grade999forvariablenames?Thinkofthefactthatyouwouldneedtodeclareallofthese.Ifyouwantedtoinputvaluesyouwouldhavetodo1000inputstatements.Outputforallwouldrequire1000outputstatements.And,evenworst,thinkoftryingtofindtheaverageofallofthese–youwouldneedahugearithmeticstatementtotal=(grade0+grade1+...+grade999)/1000;andprogramminglanguagescan’tdealwith...Almostalllanguagessupportsomethingtohandlethis.Arrays

AnarrayisanamedcollectionofhomogeneousitemsinwhichindividualitemsareaccessedbytheirplacewithinthecollectionTheplacewithinthecollectioniscalledanindexint[]myArray=newint[10]; //createsanarrayof10integersmyArray[0]=1; //setthefirstelementto1myArray[8]=myArray[0]; //setthenexttolastelementto//thevalueofthefirstelement11myArrayAnArray

ThatHasBeenGivenValues

i.e.Initialized

Indices…NowWeCanHandletheGradeAverageProblem–Notetheuseoftheindex!!!int[]grades=newint[1000];//assumesintegergradesintcount=0,sum=0;doubleaverage;//getinputandaddatsametimewhile(count<=1000){

System.out.println(“Enterthegradeforstudent“+ count);

grade[count]=Console.readInt(“>"); sum=sum+grade[count]; count=count+1;}average=sum/1000.0;Note:The<=wouldallowareferencetograde[1000]whichdoesn'texist.Changeto<(ordeclaregradesasnewint[1001])TheIndexofanArrayCanBeComputed!!!

Thus,thisisalegalreference:myArray[i+j]Anytimeyouhavealotofvariableswhicharestoringthesamekindofdata,usinganarrayhelpsyou

declarethevariableseasily

docomputingwithloops doI/Owiththevariables.Thekindofarrayintroducedsofarhasoneindexandiscalleda1-dimensionalarray.Mostlanguagessupportanarbitrarylargenumberofarrays.TwoDimensionalArraysdouble[][]myTable=newdouble[2][3];Thisreservesmemoryforkeep6realnumberssequentially.But,wecanthinkofthemasdisplayedinatablewith2rowsand3columns.myTable[0][2]=2.3;2.310120Remember,numberingStartswithzero!SummarySoFarWecandoinputandoutput.Wecanassignvaluestovariableswithintheprogram.Wecandirecttheflowofcontrolbyusingconditionalanditerativestatements.Otherthingstoremember:aprologuecommenttoexplainwhattheprogramdoesandtheauthor.theclassheaderpublicclassClassNamethemainmethodheader

publicstaticvoidmain(String[]args)variabledeclarations.MorePracticeProblemsWriteacompleteJavaprogramtoreadtheuser’sfirstandlastinitialsandwritethem.//Programtoreadandwriteuser’sinitials//Author’snamehere10/19/05publicclassInitials{publicstaticvoidmain(String[]args){charFisrtInitial,SecondInitial;

FirstInitial=Console.readChar("Enterthefirstinitial");

SecondInitial=Console.readChar("Enterthesecondinitial");

System.out.println(FirstInitial+“.”+SecondInitial+“.”);}}MorePracticeProblemsWriteacompleteJavaprogramthatasksforthepriceofanitemandthequantitytopurchase,andwritesthecost.//Programtocomputethecost//Author’snamehere10/19/05publicclassCost{publicstaticvoidmain(String[]args){doubleprice;

intamount;price=Console.readDouble("Entertheprice");amount=Console.readInt("Entertheamount");

System.out.println(“Thecostis“+(price*amount));}}MorePracticeProblemsWriteacompleteJavaprogramthatasksforanumber.Ifthenumberislessthan5,itiswritten,otherwisetwicethatnumberiswritten.//Programtoprocessanumber//Author’snamehere10/19/05publicclassNumber{publicstaticvoidmain(String[]args){

intnumber;number=Console.readInt("Enteranintegernumber");if(number<5)

System.out.println(number);elseSystem.out.println((2*number));}}MorePracticeProblemsWriteacompleteJavaprogramthatasksforapositiveintegern,andthenwritesallthenumbersfrom1uptoandincludingn.//Programtoprintintegersfrom1ton//Author’snamehere10/19/05publicclassPrintIntegers{publicstaticvoidmain(String[]args){

intn,k=1;n=Console.readInt("Enterapositiveinteger");while(k<=n){

System.out.println(k);k=k+1;}}}Subprograms

Let'splanaparty.Todothis,wehaveseveraltaskstodowhichcouldbethoughtofasorganizedinahierarchicalfashion.Subprograms

Thistypeofbreakdowniscriticalinallowingustowriteverylargeprogramswhenteamsofpeoplemustworkonthedesignandthecoding.Infact,suchabreakdownisusefulforthesingleprogrammerasitallowsustotakeacomplextaskandbreakitintosimplertaskswhichwecanconceptualizeandhandleeasier.Infact,inscienceweoftendothis:Solvesimplerproblemsandcombinesolutionstohandleharderproblems!!!SubprogramsMostprogramminglanguagesprovidesomemeansof“modularizing”orsubdividingthecodeintosubunits.Thesesubunitsarecalledbydifferentnames:functions,subroutines,subprograms,procedures,methods,etc.Inthecases1wewillconsiderhere,thereisacallingprogram–thecodethatexplicitlyinvokesor callsthesubprogramthesubprogram–thecodethatbeginsexecuting whencalled1Thereareotherwaystocallasubprogram.Forexample,itmightbecalledbyaneventsuchasamouseclick.Thattypeofsubprogramisusedalotingraphicswork.SubprogramsBasically,inoursituation,therearetwotypesofsubprograms:1)Thosethatdoaparticulartask,whichmayincludeoutput,butdonotreturnanyvalueto