C++ programing for beginners · • Define variable as a portion of memory to store a value. • C++ is a high-typed language, every variable needs to have a type, define the kind

Lecture2

C++programingforbeginners

19April2019

Lecturer:Dr.AnleWang&Dr.SergeySukhomlinov

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E-mail:[email protected]

mailto:[email protected]

Lecture2

• RememberthebasicstructureofaC++program(library,function,variables,statements,return)• NEVERmissapartofcurlybrace{},semicolon;attheendofstatement.• Useindentationandalsomakeitreadable.•

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Somecommentsofcoding

Lecture2

• Explorebasicdatatypes,basicoperators,declarationofavariable;• Discoverhowtousearithmeticoperations;• Learnsimpleinputandoutputstream(cin,cout,cerr,clog).

• Afterthislecture,youshouldbeableto:✓BefamiliarwiththebasiccomponentsofaC++program;

✓Declarationofavariable,performsimplearithmeticoperationsandinputoroutputwhatyouwant,displayonscreen.

✓Becomefamiliarwiththeusagewithincrementanddecrementoperator.

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ContentsofLecture2

Lecture219April2019 �4

AdetailedlookatC++codecomments

libraries

functions

• Asimpleprogrammustcontainsomebasiclibrariesandfunctions.Rememberthatmainfunctionisnecessary.


AdetailedlookatC++code

• Lines beginning with a hash sign (#) are directives readand interpreted by preprocessor. They are special linesinterpretedbeforethecompilation.

• For different function, search the internet to findproperlibrary. Here #include <iostream> defines the input andoutputoperationonscreen.


AdetailedlookatC++code

• Themainfunctioniscalledbytheoperatingsystemwhentheprogramstarts.

• AllC++programsmustdefineamainfunction.• Nowwewilllookintomoredetailsinthefunction,such

asvariables,operators,etc.

intmain(){declarevariablesstatementsreturn0;}

• Definevariableasaportionofmemorytostoreavalue.• C++isahigh-typedlanguage,everyvariableneedstohaveatype,definethekindofdatastored.✓C++definesnumbersofbasicdatatypes,suchasint,float,etc.✓TheC++libraryincludesmoretypes.✓Thetypeofavariablecannotbechangesatrun-time.

•Wemustdefineavariablebeforeusingit.

Whatisavariable?

Datatype variables setvaluetovariables

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• Consistofletters,digitsandtheunderscorecharacter(_);• Mustbeginwithaletterorunderscore;• Casesensitive:sum!=SUM• Illegalidentifiers:✓ helloworld(nospacebetweenletters)✓ helloworld!(noexclamation)✓ hello+world(nosymbol)✓ 1helloworld(identifiercannotbeginwithadigit)✓ double,if(keywordtoidentifydatatypes,operators)

Howtonameavariable?


• Datatype:setofvaluestogetherwithasetofoperations.• C++datatypes:✓simple.✓structured.✓pointer.• SimpleC++datatypes:✓integral:numberswithdecimal.✓floating-point:decimalnumbers.✓enumeration:user-defineddatatype.✓char:singlecharacter,suchas‘$’.✓booleandatatype:trueorfalse.

Fundamentaldatatypes


Fundamentaldatatypes

http://www.cplusplus.com/doc/tutorial/variables/�10Lecture218April2019

http://www.cplusplus.com/doc/tutorial/variables/

• char:Thesmallestintegraldatatype(1byte);• forcharacters:letters,digits,specialsymbols.• Insinglequotes:‘0’,‘#’,‘A’…• Whatis‘’?

• booltype:twovalues(true,false).• manipulateBooleanlogicaloperation.

Fundamentaldatatypes(char,bool)


• integralnumberswithoutdecimal(4byte);• Neverusecommainanintegralnumber;• 12,-25697,• Positiveintegersdonotneedtohave+sign.• Findthedifferencebetweenfollowingexpression:2/3,2.0/3,2.0/3.0

Fundamentaldatatypes(int)


• decimalnumber,scientificnotationinC++language;• floating-pointdatatype:✓float;(6-7digits)✓double;(12digits)✓longdouble;• maximumdigitsofadecimalnumber.• setprecisionforfloatingdatatype.setprecision

Fundamentaldatatypes(floating-point)


• typeidentifier=initial_value;//c-likeinitialization• typeidentifier(initial_value);//structureinitialization• typeidentifier{initial_value}.//uniforminitialization

Declarationandinitializationofavariable


Datatype variables setvaluetovariables

• Declareavariablebeforeuseit;• Whenavariableisdeclaredinonefunction,thevariablecanbeonlyaccessedinthisfunction.• Variableswillbelocalizedwhenweapplyablock(brace{})whentheyaredeclared.(scope)

Declarationofavariable


• giveanametoaconstant;• theconstantvariablewillnotchangethevalueduringrunning-time.

• Useofpreprocessordefinitiontonameavalue.• #definelineispreprocessordirective.• Note:NOSEMICOLONINPREPROCESSORDEFINITION.

Declarationofaconstant


• Expressionsarestatementsfortypicalcalculations.• Here“+”isanoperator,whichevaluatethevalueofvariable1andvariable2.• Withanoperator,thevalueofvariablescanbechanged.• C++arithmeticoperators:+(addition),-(subtraction),*(multiplication),/(division),%(modulooperator)• Orderofprecedencefollowsmathematicalrule(discusslater).3-2*5/11=?7-6./5=?11.2-2.5/3.=?

Basicoperators


• operatorssuchas:+=,-=,*=,/=,%=a+=bisthesametoa=a+b;• incrementanddecrementoperator:✓i++;++i;i--;--i;✓pre-incrementandpost-increment;✓pre-decrementandpost-decrement;

• Findthedifferencefollowingexpressions:

Basicoperators


• Twoexpressioncomparedusingrelationalandcomparisonoperators.• Resultiseithertrueorfalse.• ==(equalto),>=(largerthanorequalto),<=(lessthanorequalto),>(largerthan),<(lessthan),!=(notequalto)• a=bb,setvaluebtoa,assignment• a==btrueifaequaltob,equality• Question:Isa=bequivalenttob=a?• Isa==bequivalenttob==a?

Basicoperators(relationalandcomparison)


• booloperators:!,&&,||• !istheoperatorNOTforbooloperator.• &&and||operator:booloperatorANDandOR.

• conditionalternaryoperator(?)• condition?result1:result2• iftheconditionistrue,thevalueisresult1,otherwisethevalueisresult2.

Basicoperators


• y=1+(x=5);• x=y=z=6;• (6+3)<=(1+2);• x/=y+6;• x=5;y=x++;cout<<y;• 7==5;• x=7+2%5;• 7==5+2?a,b

Basicoperators(exercise)


Programanalysis-coding-executioncycle




Findtheperimeterandareaofarectangle.

perimeter=2*(length+width);area=length*width

Algorithm:1. Getthelengthoftherectangle;2. Getthewidthoftherectangle;3. Findtheperimeterbytheexpression;4. Findtheareausingtheequation.

Programanalysis-coding-executioncycle(example)


Everysalespersonhasabasesalary.Thesalespersonalsoreceivesabonusat theendofeachmonth,basedon the following criteria: Ifthe salesperson has been with the store for five years or less, thebonus is $10 for each year that he or she hasworked there. If thesalesperson has been with the store for more than five years, thebonus is $20 for each year that he or she has worked there. Thesalespersoncanearnanaddiyonalbonusasfollows:Ifthetotalsalesmade bythesalespersonforthemonthareatleast$5,000butlessthan$10,000,heorshereceivesa3%commissiononthesale.Ifthetotal sales made by the salesperson for the month are at least$10,000,heorshereceivesa6%commissiononthesale.



Definevariables:

BaseSalary:basesalary

noofServiceYears:numberofserviceyears

totalSales:totalsalesmadebythesalesperson

addiDonalBonus:addiyonalbonus

Algorithm:

if(noofServiceYearsislessthanorequaltofive)

bonus=10*noOfServiceYears

otherwise




Nextdeterminetheaddiyonalbonus:

if(totalSalesislessthan5000)

addiDonalBonus=0

otherwise

if(totalSalesisgreaterthanorequalto5000andtotalSalesislessthan10000)

addiDonalBonus=totalSales*0.03

otherwise


Finally,getthepaycheck.



Algorithm:

1. getbaseSalary;

2. getnoOfServiceYears;

3. checkbonususingthefollowingformula:

if(noofServiceYearsislessthanorequaltofive)


otherwise


4.gettotalSales;

5.CalculateaddiDonalBonususingfollowingformula:



if(totalSalesislessthan5000)

addiDonalBonus=0

otherwise

if(totalSalesisgreaterthanorequalto5000andtotalSalesislessthan10000)


otherwise


6.CalculatepayCheckusingequayon:

payCheck=baseSalary+bonus+addiDonalBonus

• Todisplaythetexttoscreen,wesendittoobjectcoutusinginsertionoperator<<.• Togetinputbykeyboard,wesendittoobjectcinusingextractionoperator>>.

• Trytowriteasimpleaddoperationonyourcomputer.

Displaytheresultwithstreams

• Statementsandcontrolflow(if,while,for,case…)• functions.

Nextlecture


Documents

C++ programing for beginners · • Define variable as a portion of memory to store a value. • C++ is a high-typed language, every variable needs to have a type, define the kind