C程序设计基础 英文版 课件 0.Lecture Introduction、Chapter1 Introducing C、Chapter 2 Data Types and Expressions

IntroductiontoProgramminginCPrograminginCTheoryCourseTextbookC程序设计基础(英文版)TextbookDepartment2MOOC(Chinese)3(Chinese)/course/NPU1-1457957182ClickthegreenbuttontojointhecourseMOOC(Chinese)45(English)/en/mooc/course/NPU1-1457957182MOOC(English)UsethisEnglishlinktologinifyoudon’thaveaChinesecellphone6IfyouhaveaGOOGLEaccountorGMAIL,thenchooseyouraccountEnteryourpassword.

Itmayaskyoutotypeinyourphonenumberafterthis.Round89Watchthevideos10Doyourhomeworks1112Askquestions13Changeyourusername1415YourIDorname16Xuetangonline/course/nwpu0809fu042313intl/5913023?channel=learn_titlepersonalprofile:Ucansetyournamehere.CollaborationandCheatingPolicyYouarewelcometodiscussassignmentswithotherstudents,providedthatallworkturnedinmustbeyourown.Cheatingwillnotbetolerated.19WhydoweneedC?ProgramminginCisabasiccourse.WecanlearnhowtowriteandrunaprogramItalsoisabasicforotherprogramminglanguage,suchasjava,C++etc.Cprogramminglanguagewasdesignedonearlyof1970,butisstillverypopularintheworld.20Whyweneedit?PopularityofLanguagesinTIOBEIndex21Courserequirement--KnowledgeMasterCdatatypesandexpression,canwritedifferentkindsofexpressioninC.Master3basiclogicalcontrolflow,canuse

these3basiclogicalcontrolflowtodesignprograms.Mastercommonfunctions,includingfunction

design,usageandparameters.

MasterCprogramstructureandsimplealgorithm.22Courserequirement-SkillsMasterhowtoreadandanalyzeCprogramMasterhowtodesignandwriteCprogram.MasterhowtodebugandrunCprogram.MastertheuseofanIDE(integrateddevelopmentenvironment)Understanderrorandwarningmessageandknowhowtodealwiththem.23TheEnd24Chapter1IntroducingCOutlinesChapter1IntroducingC1.1WhyProgrammingisImportant1.2WhyShouldWeLearnC1.3HistoryofC1.4StrengthsandWeaknessesofC1.5HowDoWeLearnC261.1WhyProgrammingisImportant?BeusedtoCommunicateLanguage+ProgrammingCprogrammingLanguageisawidelyusedhighlevelcomputerlanguage.27Whatisit?ProgramminginCWriteprogramsMakecomputerworkforus.28WhyShouldWeLearnC?IsCtheonlyprogramminglanguage?52’’29WhyShouldWeLearnC?1+1indifferentlanguage30#include<stdio.h>intmain(){printf("%d\n",1+1);return0;}2.1WritingaSimpleProgramCompilingandLinkingBeforeaprogramcanbeexecuted,threestepsareusuallynecessary:Preprocessing.Thepreprocessorobeyscommandsthatbeginwith#(knownasdirectives)Compiling.Acompilerthentranslatestheprogramintomachineinstructions(objectcode).Linking.Alinker

combinestheobjectcodeproducedbythecompilerwithanyadditionalcodesneededtoyield

acompleteexecutableprogram.312.1WritingaSimpleProgramTheGCCCompilerGCCisoneofthemostpopularCcompilers.GCCissuppliedwithLinuxbutisavailableformanyotherplatformsaswell.322.1WritingaSimpleProgramIntegratedDevelopmentEnvironmentsAnintegrateddevelopmentenvironment(IDE)isasoftwarepackagethatmakesitpossibletoedit,compile,link,execute,anddebugaprogramwithoutleavingtheenvironment.33Howdoesitwork?WriteaprogramwithIDE（IntegratedDevelopmentEnvironment）Talk(xxx.corxxx.cpp)Compiletheprogramtoanexecutablefile–Translate(xxx.exe)Runtheexecutablefileoncomputer--Communicate341.3HistoryofCOriginsofCCisaby-productofUNIX,developedatBellLaboratoriesbyKenThompson,DennisRitchie,andothers.KenThompson

designedasmalllanguagenamedB,basedonBCPL.By1971,DennisRitchiebegantodevelopanextendedversionofB.HecalledhislanguageNB(“NewB”)atfirst.AsthelanguagebegantodivergemorefromB,hechangeditsnametoC.Thelanguagewasstableenoughby1973thatUNIXcouldberewritteninC.351.3HistoryofCStandardizationofC-------grammarK&RCDescribedinKernighanandRitchie,TheCProgrammingLanguage(1978)DefactostandardC89/C90ANSIstandardX3.159-1989(completedin1988;formallyapprovedinDecember1989)InternationalstandardISO/IEC9899:1990C99InternationalstandardISO/IEC9899:1999IncorporateschangesfromAmendment1(1995)361.3HistoryofCC-BasedLanguagesChasahugeinfluenceonmodern-dayprogramminglanguages.C++includesallthefeaturesofC,butaddsclassesandotherfeaturestosupportobject-orientedprogramming.JavaisbasedonC++andthereforeinheritsmanyCfeatures.C#isamorerecentlanguagederivedfromC++andJava.371.4StrengthsandWeaknessesofCStrengthsofCEasytocomprehendEfficiency:Cprogramcanrunquicklyandinlimitedamountsofmemory.CprogramsexecutemorequicklythanJavaandPythondo.Power:C’slargecollectionofdatatypesandoperatorshelpmakeitapowerfullanguage.

Portability:NottiedtoanyoneOperatingsystemormachineFlexibility:CimposesveryfewrestrictionsontheuseofitsfeaturesStandard

library:OneofC’sgreatstrengthsisitsstandardlibrary,whichcontainshundredsoffunctionsforinput/output,stringhandling,storageallocationandotherusefuloperations.381.2StrengthsandWeaknessesofCWeaknessesofCLackofobject-orientedprogrammingconceptsProgrammingskillsrequiredtolearn,sinceCProgramscanbeerror-prone.Programscanbedifficulttounderstand.Programscanbedifficulttomodify.LargeprogramswritteninCcanbehardtochangeiftheyhaven’tbeendesignedwithmaintenanceinmind.NotefficientascomparedtoPython.ThesyntaxofPythoniseasierAbsenceoftheconceptofnamespaceWithoutnamespaces,wecan’tdeclaretwofactors,likevariables,withthesamename.391.5Howtolearnit?PracticeisthemagicwordtolearnCKnowledge—learnthegrammar,keywordofC

programminglanguageSkill—learnhowtowrite,compileandrunC

program40Whenyoudon’tPRACTICECODEBLOCKSTheplacetowritethecode--codeblocksWheretowritethecode--codeblocksDownloadcodeblocksfromHowtouseit42Wheretowriteyourprogram------------CodeBlocks

1.Goto：/downloads2.Click“Downloadthebinaryrelease”3.

Pleaseselectasetuppackagedependingonyourplatform:

E.g.WeuseWINDOWS：

3.Pleaseselectasetuppackagedependingonyourplatform:E.g.WeuseWINDOWS：

Pleaseselect“codeblocks-20.03minGW-setup.exe”。ClickDownloadfrom"FossHUB"

or"S"(Theyarethesame).（IfyoucannotinstallCODEBLOCKS，thendownload“codeblocks-20.03mingw-nosetup.zip”.Youdon'thavetoinstallit,justdownloaditthenyoucanuseit.）

4.Afteryoudownloadthefiles,clickitandsetupCode::Blocks.Note：Code::Blockswillbeinstalledinthedefaultfolder“C:\ProgramFiles\CodeBlocks”.Youshouldchangetoanotherfolder.TheruleistoavoidusingSPACEorChinesecharactersintheinstallationpath.However,between“Program”and“Files”,thereisaspace.So,youshoulduseadifferentfolder.Click“Browse..."tochangethefolderyouinstallitin，E.g.Ichangetoc:\mysoftwareYoucaninstallitdirectlyattherootdirectoryofdiskCordiskD,etc.Youcanalsoinstallitinotherplaces.Forexample,youcancreateanewfoldercalled“mysoftware”onyourdiskDandinstallCode::Blocksinthisnewfolder.Click“Browse...”tochangethefolderyouwanttoinstallitin.Forexample,wecanchangeitto“C:\mysoftware\CodeBlocks”Nowyoucanusecoldclocks.

Ifyouinstallandunsetupitmanytimes,youmaymeetsomeerrorslike"Can'tfindtheGNUGCCCompiler".PleaseseemyAnnouncement”Can'tfindacompiler“474849Typethe

name

of

yourproject

as

you

like

,c101,c102….e.g.Then

choosethe

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tocreate

yourproject

in

by

clicking

thisbutton505115223Ifu

want

open

your

code

again11xcode56Mac

OS1.

Install

XCODEfromtheAppstore.2.

OpenXCODEthen

clickCreate

anew

XCODEproject572. ChooseCommand

LineTool

then

clicknext58•3.

type

thenameofyourproject59week1ex16061• 6.1622• 6.1632OnlineCompilerhttps://www.onlinegdb.com/online_c_compiler#1234TheEnd67Chapter2DataTypesandExpressionsOutlineChapter2DataTypesandExpressions2.1TheGeneralFormofaSimpleProgram2.2CharacterSetandKeywords2.3DataTypes2.4VariablesandConstants2.5OperatorsandExpressions69IntegratedDevelopmentEnvironmentsCode::Blocks702.1TheGeneralFormofaSimpleProgramNOTE:•Crequiresasemicolon(;)attheendofeverystatement.•statement.printfisastandardCfunction--calledfrommain.•Statementsshouldbeenclosedinbraces.•“\n”signifiesnewline.Formattedoutput--morelater.•Casesensitive,printfandPrintfaredifferent.•Linenumbercanbeshowninaneditor,itisnotthecontentofprogram.712.1TheGeneralFormofaSimpleProgram2.2TheGeneralFormofaSimpleProgramSimpleCprogramshavetheformwiththreeparts

directives

intmain()

{

statements

}EventhesimplestCprogramsrelyonthreekeylanguagefeatures:DirectivesFunctionsStatements722.2TheGeneralFormofaSimpleProgramDirectivesBeforeaCprogramiscompiled,itisfirsteditedbyapreprocessor.Commandsintendedforthepreprocessorarecalleddirectives.Example:

#include<stdio.h>stdio.h

isaheadercontaininginformationaboutC’sstandardI/Olibrary.Directivesalwaysbeginwitha#character.there’snosemicolonorotherspecialmarkerattheend.732.2TheGeneralFormofaSimpleProgramFunctionsAfunctionisaseriesofstatementsthathavebeengroupedtogetherandgivenaname.Afunctionisusuallydesignedtoperformaspecifictask.Libraryfunctionsare

providedaspartoftheCimplementation.74XXXXXX(XXX)

{

statements

}intmain()

{

statements

}2.2TheGeneralFormofaSimpleProgramThemainFunction

isspecialEveryCprogrammusthaveoneandonlyonemainfunctionsomewhere.main

isspecial:itgetscalledautomaticallywhentheprogramisexecuted.Thewordintjustbeforemainindicatesthemainfunctionreturnsanintegervalue.main

returnsacode;thevalue0indicatesnormalprogramtermination.Ifthere’snoreturn

statementattheendofthemain

function,manycompilerswillproduceawarningmessage.Thewordvoidinparentheses()indicatesthatmainhasnoarguments.(Youdon'thavetowritetheword“void”,justleaveitblank)752.2TheGeneralFormofaSimpleProgramStatements：Astatementisacommandtobeexecutedwhentheprogramruns.Crequiresthateachstatementendwithasemicolon(;)Helloworldusesonlytwokindsofstatements.Oneisthereturn

statement;theotheristhefunctioncall.Askingafunctiontoperformitsassignedtaskisknownascallingthefunction.main()callsprintf

todisplayastring:762.2TheGeneralFormofaSimpleProgramPrintingStringsTheprintf

functiondisplaysastring—charactersenclosedindoublequotationmarks(””).\n

(thenew-linecharacter)

77In-classassignment1:introduceyourselfCreateanewprojectnamed“ex01”Edityour“helloworld”anddisplay3statements:1.yournameandwhereareyoufrom2.Introduceyourcountry3.SaysomethingtoChina

Thefilenamedoesn’tmatter,butdon’tusespace.7879CommentsAcommentbeginswith/*andendwith*/.

/*Thisisthefirstlineofthecomment

Thisisthesecondlineofthecomment

*/

Commentscanalsobewritteninthefollowingway: //Thisisacomment1.CharacterLinesbetween/*and*/areacomment.2.Commentsexplainwhattheprogramdoes.3.Commentsareignoredbythecompiler.80In-classassignment2:commentsAddsomecommentsto“introduceyourself”

812.1.2TheBasicStepstoWriteaSimpleProgramWecanconsideranotherprogramthatinvolvesaddingtwonumbers,denotedasaandb82832.2CharacterSetandKeywordsAcharactersetisasetofalphabets,digits,andsomespecialcharactersthatarevalidintheClanguage.(1)AlphabetsUppercase:ABCDEFGHIJKLMNOPQRSTUVWXYZLowercase:abcdefghijklmnopqrstuvwxyz(2)Digits0123456789(3)SpecialCharacters<>._();$:%[]#?'&{}"^!*/|-\～+842.2.2Keywords852.2.3Identifiers---------NAMESNamesforvariables,functions….arecalledidentifiers.Anidentifiermaycontainletters,digits,andunderscores,butmustbeginwithaletterorunderscore: times10get_next_char

Examplesofillegalidentifiers:

10timesget-next-charCiscase-sensitive:itdistinguishesbetweenupper-caseandlower-caselettersinidentifiers.Forexample,thefollowingidentifiersarealldifferent:

jobjoBjObjOBJobJoBJObJOB862.3DataTypes87DataTypesvshotelrooms88A

bit

storesjusta0or1.

Inthecomputerit'sall0'sand1’s.Group8bitstogethertomake1byte.Onebyte=collectionof8bits.1

Byte

=8bitsTypes------thesizeoftheemptybox/roomEveryvariablemusthaveatype.eg.

int

、

float、double

andchar.sizeMLXLS

storedata3312.3or99999999999‘a’Avariableoftypefloat

(shortforfloating-point)、double

canstoremuchlargernumbersthananint

variable.Also,afloat/double

variablecanstorenumberswithdigitsafterthedecimalpoint,like379.125.89Rangeandsizetype[signed]intunsigned[int][signed]short[int]unsignedshort[int][signed]long[int]unsignedlong[int][signed]charunsignedcharfloatdoublelongdoubleSize(Byte)44224411488/12Range-2147483648～+2147483647

～0～4294967295

～-32768～+32767

～0～65535

～-2147483648～+2147483647

～0～4294967295

～-128～+127

～0～255

～3.4×10−381.7×10−308precision3.4×10381.7×103081.2×104932716191.2×10−4932/CProgrammingLanguageSomebasicdatatypesTypecharshortintlongfloatdoubleDescribeAcharacterofthelocalcharactersetshortintegerintegerlongintegersingle-precisionfloatingpointdouble-precisionfloatingpointCProgrammingLanguage522.3.1IntegerTypesTheintegertypes,aredividedintotwocategories:signedandunsigned.整型分有符号整型和无符号整型Theleftmostbitofasignedinteger(knownasthesignbit)is0ifthenumberispositiveorzero,1ifit’snegative.有符号的整型数，其二进制的最左边一位是符号位。0正1负Anintegerwithnosignbit(theleftmostbitisconsideredpartofthenumber’smagnitude)issaidtobeunsigned.无符号的整型数，其二进制的最左边一位也看成是数字的一部分。922.3.1IntegerTypesSignedandUnsignedIntegersBydefault,integervariablesinCaresigned—theleftmostbitisreservedforthesign.Totellthecompilerthatavariablehasnosignbit,declareittobeunsigned.C通常默认整型变量都是有符号的。（可以用来存储负数）如果要声明数据是无符号的，int前面要加上unsigned932.3.1IntegerTypesC’sintegertypecomesindifferentsizes.intintegerisusually32bits,butmaybe16bitsonolderCPUs.Longintegersmayhavemorebitsthanordinaryintegers;shortintegersmayhavefewerbits.Int型变量一般占4个字节32位二进制的存储空间。不同的CPU会有差异。942.3.1IntegerTypesTheCstandardrequiresthatshort

int,int,andlong

intmusteachcoveracertainminimumrangeofvalues.intmustnotbeshorterthanshort

int,andlong

intmustnotbeshorterthanint.通常他们所占的存储空间是short<=int<=long952.3.1IntegerTypesOnlysixcombinationsproducedifferenttypes:

short

int

unsigned

short

int

int

unsigned

int

long

int unsigned

long

intthewordintcanbedropped(long

intcanbeabbreviatedtojustlong).

Int可以省略。比如longint可以省略成long962.3.1IntegerTypesTherangeofvaluesrepresentedbyeachofthesixintegertypesvariesfromonemachinetoanother.Typicalrangesona64-bitmachine: Type SmallestValue LargestValue short

int –32,768 32,767 unsigned

short

int 0 65,535 int –2,147,483,648 2,147,483,647 unsigned

int 0 4,294,967,295 long

int –263 263–1 unsigned

long

int 0

264–1存储范围表示了该类型的变量能存放的最大和最小的数。不同的机器上范围是不同的。972.3.1IntegerTypesIntegerTypesinC99C99providestwoadditionalstandardintegertypes,long

long

intandunsigned

long

long

int.Bothlong

longtypesarerequiredtobeatleast64bitswide.Therangeoflong

long

intvaluesistypically–263(–9,223,372,036,854,775,808)to263–1(9,223,372,036,854,775,807).Therangeofunsigned

long

long

int

valuesisusually0to264–1(18,446,744,073,709,551,615).982.3.2FloatingTypes实型----浮点数（存储小数）Cprovidesthreefloatingtypes

Type SmallestPositiveValue LargestValue Precision

float 1.17549

10–38 3.40282

1038 6digits

double 2.22507

10–308 1.79769

10308 15digitsfloat Single-precisionfloating-point单精度浮点数doubledouble-precisionfloating-point双精度浮点数long

doubleExtended-precisionfloating-pointlong

doubleisrarelyused.实型变量一般用来存储带小数的数。计算机中通常以浮动小数点的形式来存储，所以实型也叫做浮点数。实型主要分两种，float和double。两者的不同在于后者存储空间大，大约双倍精度。992.3.3CharacterTypeschargender;CharacterSetsToday’smostpopularcharactersetisASCII(AmericanStandardCodeforInformationInterchange),a7-bitcodecapableofrepresenting128characters.Ctreatscharactersassmallintegers.Thecharacter'a'hasthevalue97'A'hasthevalue65;'0'hasthevalue48‘1'hasthevalue49.

Characterconstantsactuallyhaveint

typeratherthanchartype.1002.4VariablesandConstantsVariable变量--------emptybox/roomMostprogramsneedawaytostoredatatemporarilyduringprogramexecution.Thesestoragelocationsarecalledvariables.101Variablenamevariable2.4VariablesandConstantsDeclarations定义变量-------分配相应的存储空间Todeclareavariable,wefirstspecifythetypeofthevariable,thenitsname.

类型变量名，变量名……；

intheight,length,width,volume;

floatprofit,loss;

doublevolume;

charch;作用：在内存中，为变量分配相应的存储空间，以便后面用来存放数据。102Declarations------checkinathotelVariablesmustbedeclared

beforetheyareused.

intmain()

{

intspam;//declarations定义

spam=15;//statements使用return0;

}变量一定要先定义（分配存储空间）后使用。103spam15AssignmentAssignment赋值

------往变量里面存放数据Avariablecanbegivenavaluebymeansofassignment:inth;

h=8;Thenumber8issaidtobeaconstant（常量）

. intspam;

spam=15;//youstoredthevalue15insidethevariablespam spam=3;Butwhenyouenterspam=3,thevalue15isoverwritten(thatis,replaced)withthevalue3.Theoldvalueinspamisforgotten.Aconstantassignedtoafloat/double

variableusuallycontainsadecimalpoint:

profit=2150.48;It’sbesttoappendtheletterftoafloating-pointconstantifitisassignedtoafloat

variable:

profit=2150.48f;Failingtoincludethe

f

maycauseawarningfromthecompiler.104AssignmentAnint

variableisnormallyassignedavalueoftypeint,adoublevariableisnormallyassignedavalueoftypedouble.intd;d=33;floatx;doublez;x=178.111;z=1899.111;charc1;c1=‘a’;通常：整数赋给整型变量（int），小数赋给实型变量(float,double)字符赋给字符型变量(char)Mixingtypes(suchasassigninganintvaluetoafloatvariableorassigningafloatvaluetoanintvariable)ispossiblebutnotalwayssafe.intd;d=33.6;???105AssignmentAssignmentOnceavariablehasbeenassignedavalue,itcanbeusedtohelpcomputethevalueofanothervariable:height=8;length=12;width=10;volume=height*length*width;/*volumeisnow960*/Therightsideofanassignmentcanbeaformula(orexpression,inCterminology).106107AssignmentInitialization（初始化）定义变量的同时赋初值Theinitialvalueofavariablemaybeincludedinitsdeclaration:

intheight=8;

Thevalue8issaidtobeaninitializer.

intheight=8,length=12,width=10;Eachvariablerequiresitsowninitializer.

intheight,length,width=10; /*initializesonlywidth*/107AssignmentPrintingtheValueofaVariable输出变量的值printf

canbeusedtodisplaythecurrentvalueofavariable.conversionspecification格式说明符:beginwith%

%d

isaplaceholderindicatingwherethevalueofi

istobefilledin.

ddisplayanintegerindecimalform.i=3;printf(“Ihave%dcats\n",i);108Classexercise3:introduceyourfamilyCreateanewprojectnamed“ex03”introduceyourfamilyoryourpet.Thefilenamedoesn’tmatter,butdon’tusespace.1092.4.2ConstantsIntegerConstants整型常量,整数Constantsarenumbersthatappearinthetextofaprogram.Callowsintegerconstantstobewrittenindecimal(base10十进制),65octal(base8八进制),0101orhexadecimal(base16十六进制).0x411102.4.1IntegerTypesOctalandHexadecimalNumbers八、十六进制Octalnumbersuseonlythedigits0through7.Eachpositioninanoctalnumberrepresentsapowerof8.Theoctalnumber237representsthedecimalnumber

2×82+3×81+7×80=128+24+7=159.Ahexadecimal(orhex)numberiswrittenusingthedigits0through9plusthelettersAthroughF,whichstandfor10through15,respectively.Thehexnumber1AFhasthedecimalvalue1×162+10×161+15×160=256+160+15=431.111IntegerConstantsDecimalconstantscontaindigitsbetween0and9,butmustnotbeginwithazero:十进制整型常量

1525532767Octalconstantscontainonlydigitsbetween0and7,andmustbeginwithazero:八进制整型常量用0开头

0170377077777Hexadecimalconstantscontaindigitsbetween0and9andlettersbetweenaandf,andalwaysbeginwith0x:十六进制整型常量用0x开头

0xf0xff0x7fffThelettersinahexadecimalconstantmaybeeitherupperorlowercase:

0xff0xfF0xFf0xFF0Xff0XfF0XFf0XFF112IntegerConstantsThetypeofadecimalintegerconstantisnormallyint.Toforcethecompilertotreataconstantasalonginteger,justfollowitwiththeletterL(orl):

15L

0377L

0x7fffLToindicatethataconstantisunsigned,puttheletterU(oru)afterit:

15U

0377U

0x7fffULandUmaybeusedincombination:

0xffffffffUL

TheorderoftheLandUdoesn’tmatter,nordoestheircase.十进制整数比如15会被默认为int型，如果想强制编译器把该数认为long型或者无符号整型。就要在数字后面加L或者U.(L,U可以小写）113IntegerConstantsinC99InC99,integerconstantsthatendwitheitherLL

orll(thecaseofthetwolettersmustmatch)havetypelong

long

int.AddingtheletterU(oru)beforeoraftertheLLorlldenotesaconstantoftypeunsigned

long

long

int.C99’sgeneralrulesfordeterminingthetypeofanintegerconstantareabitdifferentfromthoseinC89.Thetypeofadecimalconstantwithnosuffix(U,u,L,l,LL,orll)isthe“smallest”ofthetypesint,long

int,orlong

long

intthatcanrepresentthevalueofthatconstant.114ReadingandWritingIntegers八、十六、无符号数输入输出格式符Readingandwritingunsigned,short,andlongintegersrequiresnewconversionspecifiers.Whenreadingorwritinganunsignedinteger,usetheletteru,o,x

insteadofdintheconversionspecification.

%u%o%x

unsignedintu;

scanf("%u",&u);/*readsuinbase10*/ printf("%u",u);/*writesuinbase10*/ scanf("%o",&u);/*readsuinbase8*/ printf("%o",u);/*writesuinbase8*/ scanf("%x",&u);/*readsuinbase16*/ printf("%x",u);/*writesuinbase16*/115ReadingandWritingIntegers十、八、十六、无符号数输入输出格式符Whenreadingorwritingashortinteger,puttheletterhinfrontofd,o,u,orx:%hd%ho%hu%hx

shorts;

scanf("%hd",&s); printf("%hd",s);Whenreadingorwritingalonginteger,puttheletterl

infrontofd,o,u,orx.%ld%lo%lu%lxWhenreadingorwritingalong

long

integer(C99only),putthelettersllinfrontofd,o,u,orx.116FloatingConstants实型常量（小数）Floatingconstantscanbewritteninavarietyofways.Validwaysofwritingthenumber57.0:

57.057.57.0e057E05.7e15.7e+1 .57e2570.e-1Afloatingconstantmustcontainadecimalpointand/oranexponent;theexponentindicatesthepowerof10bywhichthenumberistobescaled.Ifanexponentispresent,itmustbeprecededbytheletterE

(ore).Anoptional+or-signmayappearaftertheE(ore).TheremustbeanumberbeforeandafterE,andthenumberafterEmustbeaninteger小数就是实型常量。可以写成小数或者科学记数法两种形式。注意：E前后必须有数字，E后必须为整数117TheremustbeanumberbeforeandafterE,andthenumberafterEmustbeaninteger注意：E前必须有数字，E后必须为整数118FloatingConstantsBydefault,floatingconstantsarestoredasdouble-precisionnumbers.Toindicatethatonlysingleprecision(float)isdesired,puttheletterF(orf)attheendoftheconstant(forexample,57.0F).Toindicatethataconstantshouldbestoredinlong

doubleformat,puttheletterL(orl)attheend(57.0L).

小数比如57.0会被默认为double类型的常量，如果要强制编译器把它看成float类型。就在后面加f。119ReadingandWritingFloating-PointNumbers%e,%f,and%gareusedforreadingandwritingsingle-precisionfloating-pointnumbers.Whenreadingavalueoftypedouble,puttheletterlinfrontofe,f,org:

floatd; scanf("%f",&d);printf("%f",d); doubled; scanf("%lf",&d);printf("%f",d);Note:Uselonlyinascanfformatstring,notaprintfstring.120CharacterconstantsCharacterSetsAvariableoftypecharcanbeassignedanysinglecharacter: charch1，ch2,ch3,ch4;

ch1='a';/*lower-casea*/97 ch2='A';/*upper-caseA*/65 ch3='0';/*zero*/48 ch4='';