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miniC++

C++LanguageTutorial

Bywill,2010-12-13

1．Introduction1

2．Structureofaprogram2

3．VariablesandDataTypes4

4．Constants8

5．Operators9

6．BasicInput/Output15

7．ControlStructures19

8．Functions（I）26

9．Functions（II）30

10．Arrays34

11．CharacterSequences39

12．Pointers41

13．Input/Outputwithfiles49

1．Introduction

C++isastaticallytyped,free-form,multi-paradigm,compiled,general-purposeprogramminglanguage.Itisregardedasa"middle-level"language,asitcomprisesacombinationofbothhigh-levelandlow-levellanguagefeatures.ItwasdevelopedbyBjarneStroustrupstartingin1979atBellLabsasanenhancementtotheClanguageandoriginallynamedCwithClasses.ItwasrenamedC++in1983.

Asoneofthemostpopularprogramminglanguagesevercreated,C++iswidelyusedinthesoftwareindustry.Someofitsapplicationdomainsincludesystemssoftware,applicationsoftware,devicedrivers,embeddedsoftware,high-performanceserverandclientapplications,andentertainmentsoftwaresuchasvideogames.SeveralgroupsprovidebothfreeandproprietaryC++compilersoftware,includingtheGNUProject,Microsoft,IntelandEmbarcaderoTechnologies.C++hasgreatlyinfluencedmanyotherpopularprogramminglanguages,mostnotablyC#andJava.

1.1Structureofthistutorial

Thetutorialisdividedinthirteensectionscoveringonespecifictopiceach.Youcanaccessanysectiondirectlyfromthesectionindexavailable,orbeginthetutorialfromanypointandfollowthelinksatthebottomofeachsection.

Manysectionsincludeexamplesthatdescribetheuseofthenewlyacquiredknowledgeinthechapter.Itisrecommendedtoreadtheseexamplesandtobeabletounderstandeachofthecodelinesthatconstituteitbeforepassingtothenextchapter.

Agoodwaytogainexperiencewithaprogramminglanguageisbymodifyingandaddingnewfunctionalitiesonyourowntotheexampleprogramsthatyoufullyunderstand.Don'tbescaredtomodifytheexamplesprovidedwiththistutorial,that'sthewaytolearn!

1.2Compilers

Theexamplesincludedinthistutorialareall consoleprograms.Thatmeanstheyusetexttocommunicatewiththeuserandtoshowtheirresults.

AllC++compilerssupportthecompilationofconsoleprograms.Checktheuser'smanualofyourcompilerformoreinfoonhowtocompilethem.

2．Structureofaprogram

Thebestwaytostartlearningaprogramminglanguageisbywritingaprogram.Therefore,hereisourfirstprogram:

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//myfirstprograminC++

#include

usingnamespacestd;

intmain（）

{

cout<<"HelloWorld!

";

return0;

}

HelloWorld!

Thefirstpanel（inlightblue）showsthesourcecodeforourfirstprogram.Thesecondone（inlightgray）showstheresultoftheprogramoncecompiledandexecuted.Totheleft,thegreynumbersrepresentthelinenumbers-thesearenotpartoftheprogram,andareshownheremerelyforinformationalpurposes.

Thepreviousprogramisthetypicalprogramthatprogrammerapprenticeswriteforthefirsttime,anditsresultistheprintingonscreenofthe"HelloWorld!

"sentence.ItisoneofthesimplestprogramsthatcanbewritteninC++,butitalreadycontainsthefundamentalcomponentsthateveryC++programhas.Wearegoingtolooklinebylineatthecodewehavejustwritten:

//myfirstprograminC++

Thisisacommentline.Alllinesbeginningwithtwoslashsigns（//）areconsideredcommentsanddonothaveanyeffectonthebehavioroftheprogram.Theprogrammercanusethemtoincludeshortexplanationsorobservationswithinthesourcecodeitself.Inthiscase,thelineisabriefdescriptionofwhatourprogramis.

#include

Linesbeginningwithahashsign（#）aredirectivesforthepreprocessor.Theyarenotregularcodelineswithexpressionsbutindicationsforthecompiler'spreprocessor.Inthiscasethedirective #include tellsthepreprocessortoincludetheiostreamstandardfile.Thisspecificfile（iostream）includesthedeclarationsofthebasicstandardinput-outputlibraryinC++,anditisincludedbecauseitsfunctionalityisgoingtobeusedlaterintheprogram. 

usingnamespacestd;

AlltheelementsofthestandardC++libraryaredeclaredwithinwhatiscalledanamespace,thenamespacewiththename std.Soinordertoaccessitsfunctionalitywedeclarewiththisexpressionthatwewillbeusingtheseentities.ThislineisveryfrequentinC++programsthatusethestandardlibrary,andinfactitwillbeincludedinmostofthesourcecodesincludedinthesetutorials.

intmain（）

Thislinecorrespondstothebeginningofthedefinitionofthemainfunction.ThemainfunctionisthepointbywhereallC++programsstarttheirexecution,independentlyofitslocationwithinthesourcecode.Itdoesnotmatterwhetherthereareotherfunctionswithothernamesdefinedbeforeorafterit-theinstructionscontainedwithinthisfunction'sdefinitionwillalwaysbethefirstonestobeexecutedinanyC++program.Forthatsamereason,itisessentialthatallC++programshavea main function.

Theword main isfollowedinthecodebyapairofparentheses（（））.Thatisbecauseitisafunctiondeclaration:

InC++,whatdifferentiatesafunctiondeclarationfromothertypesofexpressionsaretheseparenthesesthatfollowitsname.Optionally,theseparenthesesmayenclosealistofparameterswithinthem.

Rightaftertheseparentheseswecanfindthebodyofthemainfunctionenclosedinbraces（{}）.Whatiscontainedwithinthesebracesiswhatthefunctiondoeswhenitisexecuted.

cout<<"HelloWorld!

";

ThislineisaC++statement.Astatementisasimpleorcompoundexpressionthatcanactuallyproducesomeeffect.Infact,thisstatementperformstheonlyactionthatgeneratesavisibleeffectinourfirstprogram.

cout isthenameofthestandardoutputstreaminC++,andthemeaningoftheentirestatementistoinsertasequenceofcharacters（inthiscasethe HelloWorld sequenceofcharacters）intothestandardoutputstream（cout,whichusuallycorrespondstothescreen）.

cout isdeclaredinthe iostream standardfilewithinthe std namespace,sothat'swhyweneededtoincludethatspecificfileandtodeclarethatweweregoingtousethisspecificnamespaceearlierinourcode.

Noticethatthestatementendswithasemicoloncharacter（;）.ThischaracterisusedtomarktheendofthestatementandinfactitmustbeincludedattheendofallexpressionstatementsinallC++programs（oneofthemostcommonsyntaxerrorsisindeedtoforgettoincludesomesemicolonafterastatement）.

return0;

Thereturnstatementcausesthemainfunctiontofinish.returnmaybefollowedbyareturncode（inourexampleisfollowedbythereturncodewithavalueofzero）.Areturncodeof0 forthe main functionisgenerallyinterpretedastheprogramworkedasexpectedwithoutanyerrorsduringitsexecution.ThisisthemostusualwaytoendaC++consoleprogram.

Youmayhavenoticedthatnotallthelinesofthisprogramperformactionswhenthecodeisexecuted.Therewerelinescontainingonlycomments（thosebeginningby //）.Therewerelineswithdirectivesforthecompiler'spreprocessor（thosebeginningby #）.Thentherewerelinesthatbeganthedeclarationofafunction（inthiscase,themainfunction）and,finallylineswithstatements（liketheinsertioninto cout）,whichwereallincludedwithintheblockdelimitedbythebraces（{}）ofthemainfunction.

InC++,theseparationbetweenstatementsisspecifiedwithanendingsemicolon（;）attheendofeachone,sotheseparationindifferentcodelinesdoesnotmatteratallforthispurpose.Wecanwritemanystatementsperlineorwriteasinglestatementthattakesmanycodelines.Thedivisionofcodeindifferentlinesservesonlytomakeitmorelegibleandschematicforthehumansthatmayreadit.

Comments

Commentsarepartsofthesourcecodedisregardedbythecompiler.Theysimplydonothing.Theirpurposeisonlytoallowtheprogrammertoinsertnotesordescriptionsembeddedwithinthesourcecode. 

C++supportstwowaystoinsertcomments:

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//linecomment

/*blockcomment*/

Thefirstofthem,knownaslinecomment,discardseverythingfromwherethepairofslashsigns（//）isfounduptotheendofthatsameline.Thesecondone,knownasblockcomment,discardseverythingbetweenthe /* charactersandthefirstappearanceofthe */ characters,withthepossibilityofincludingmorethanoneline.

Wearegoingtoaddcommentstooursecondprogram:

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/*mysecondprograminC++withmorecomments*/

#include

usingnamespacestd;

intmain（）

{

cout<<"HelloWorld!

";//printsHelloWorld!

cout<<"I'maC++program";//printsI'maC++program

return0;

}

HelloWorld!

I'maC++program

Ifyouincludecommentswithinthesourcecodeofyourprogramswithoutusingthecommentcharacterscombinations //, /* or */,thecompilerwilltakethemasiftheywereC++expressions,mostlikelycausingoneorseveralerrormessageswhenyoucompileit.

3．VariablesandDataTypes

Theusefulnessofthe "HelloWorld" programsshownintheprevioussectionisquitequestionable.Wehadtowriteseverallinesofcode,compilethem,andthenexecutetheresultingprogramjusttoobtainasimplesentencewrittenonthescreenasresult.Itcertainlywouldhavebeenmuchfastertotypetheoutputsentencebyourselves.However,programmingisnotlimitedonlytoprintingsimpletextsonthescreen.Inordertogoalittlefurtheronandtobecomeabletowriteprogramsthatperformusefultasksthatreallysaveusworkweneedtointroducetheconceptof variable.

LetusthinkthatIaskyoutoretaint