C程序设计语言英文版已改格式汇总Word文档下载推荐.docx

C程序设计语言英文版已改格式汇总Word文档下载推荐.docx

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toleapoverityouhavetobeabletocreatetheprogramtextsomewhere,compileitsuccessfully,loadit,runit,andfindoutwhereyouroutputwent.Withthesemechanicaldetailsmastered,everythingelseiscomparativelyeasy.

InC,theprogramtoprint'

'

hello,world'

is

#include<

stdio.h>

main（）

{

printf（"

hello,world\n"

）;

}

Justhowtorunthisprogramdependsonthesystemyouareusing.Asaspecificexample,ontheUNIXoperatingsystemyoumustcreatetheprograminafilewhosenameendsin'

.c'

suchashello.c,thencompileitwiththecommand

cchello.c

Ifyouhaven'

tbotchedanything,suchasomittingacharacterormisspellingsomething,thecompilationwillproceedsilently,andmakeanexecutablefilecalleda.out.Ifyouruna.outbytypingthecommand

a.out

itwillprint

Onothersystems,theruleswillbedifferent;

checkwithalocalexpert.

Now,forsomeexplanationsabouttheprogramitself.ACprogram,whateveritssize,consistsoffunctionsandvariables.Afunctioncontainsstatementsthatspecifythecomputingoperationstobedone,andvariablesstorevaluesusedduringthecomputation.CfunctionsarelikethesubroutinesandfunctionsinFortranortheproceduresandfunctionsofPascal.Ourexampleisafunctionnamedmain.Normallyyouareatlibertytogivefunctionswhatevernamesyoulike,but'

main'

isspecial-yourprogrambeginsexecutingatthebeginningofmain.Thismeansthateveryprogrammusthaveamainsomewhere.

mainwillusuallycallotherfunctionstohelpperformitsjob,somethatyouwrote,andothersfromlibrariesthatareprovidedforyou.Thefirstlineoftheprogram,

tellsthecompilertoincludeinformationaboutthestandardinput/outputlibrary;

thelineappearsatthebeginningofmanyCsourcefiles.ThestandardlibraryisdescribedinChapter7andAppendixB.

Onemethodofcommunicatingdatabetweenfunctionsisforthecallingfunctiontoprovidealistofvalues,calledarguments,tothefunctionitcalls.Theparenthesesafterthefunctionnamesurroundtheargumentlist.Inthisexample,mainisdefinedtobeafunctionthatexpectsnoarguments,whichisindicatedbytheemptylist（）.

Thestatementsofafunctionareenclosedinbraces{}.Thefunctionmaincontainsonlyonestatement,

Afunctioniscalledbynamingit,followedbyaparenthesizedlistofarguments,sothiscallsthefunctionprintfwiththeargument"

.printfisalibraryfunctionthatprintsoutput,inthiscasethestringofcharactersbetweenthequotes.

Asequenceofcharactersindoublequotes,like"

iscalledacharacterstringorstringconstant.Forthemomentouronlyuseofcharacterstringswillbeasargumentsforprintfandotherfunctions.

Thesequence\ninthestringisCnotationforthenewlinecharacter,whichwhenprinted

advancestheoutputtotheleftmarginonthenextline.Ifyouleaveoutthe\n（aworthwhileexperiment）,youwillfindthatthereisnolineadvanceaftertheoutputisprinted.Youmustuse\ntoincludeanewlinecharacterintheprintfargument;

ifyoutrysomethinglike

hello,world"

theCcompilerwillproduceanerrormessage.

printfneversuppliesanewlinecharacterautomatically,soseveralcallsmaybeusedtobuildupanoutputlineinstages.Ourfirstprogramcouldjustaswellhavebeenwritten

hello,"

world"

\n"

toproduceidenticaloutput.

Noticethat\nrepresentsonlyasinglecharacter.Anescapesequencelike\nprovidesageneralandextensiblemechanismforrepresentinghard-to-typeorinvisiblecharacters.

AmongtheothersthatCprovidesare\tfortab,\bforbackspace,\"

forthedoublequoteand\\forthebackslashitself.ThereisacompletelistinSection2.3.

Exercise1-1.Runthe'

programonyoursystem.Experimentwithleavingoutpartsoftheprogram,toseewhaterrormessagesyouget.

Exercise1-2.Experimenttofindoutwhathappenswhenprints'

sargumentstringcontains\c,wherecissomecharacternotlistedabove.

1.2VARIABLESANDARITHMETICEXPRESSIONS

ThenextprogramusestheformulaoC=（5/9）（oF-32）toprintthefollowingtableofFahrenheit

temperaturesandtheircentigradeorCelsiusequivalents:

1-17

20-6

404

6015

8026

10037

12048

14060

16071

18082

20093

220104

240115

260126

280137

300148

Theprogramitselfstillconsistsofthedefinitionofasinglefunctionnamedmain.Itislongerthantheonethatprinted'

butnotcomplicated.Itintroducesseveralnewideas,includingcomments,declarations,variables,arithmeticexpressions,loops,andformattedoutput.

/*printFahrenheit-Celsiustableforfahr=0,20,...,300*/

intfahr,celsius;

intlower,upper,step;

lower=0;

/*lowerlimitoftemperaturescale*/

upper=300;

/*upperlimit*/

step=20;

/*stepsize*/

fahr=lower;

while（fahr<

=upper）{

celsius=5*（fahr-32）/9;

%d\t%d\n"

fahr,celsius）;

fahr=fahr+step;

Thetwolines

/*printFahrenheit-Celsiustable

forfahr=0,20,...,300*/

areacomment,whichinthiscaseexplainsbrieflywhattheprogramdoes.Anycharactersbetween/*and*/areignoredbythecompiler;

theymaybeusedfreelytomakeaprogrameasiertounderstand.Commentsmayappearanywherewhereablank,tabornewlinecan.InC,allvariablesmustbedeclaredbeforetheyareused,usuallyatthebeginningofthefunctionbeforeanyexecutablestatements.Adeclarationannouncesthepropertiesofvariables;

itconsistsofanameandalistofvariables,suchas

Thetypeintmeansthatthevariableslistedareintegers;

bycontrastwithfloat,whichmeansfloatingpoint,i.e.,numbersthatmayhaveafractionalpart.Therangeofbothintandfloatdependsonthemachineyouareusing;

16-bitsints,whichliebetween-32768and+32767,arecommon,asare32-bitints.Afloatnumberistypicallya32-bitquantity,withatleastsixsignificantdigitsandmagnitudegenerallybetweenabout10-38and1038.Cprovidesseveralotherdatatypesbesidesintandfloat,including:

charcharacter-asinglebyte

shortshortinteger

longlonginteger

doubledouble-precisionfloatingpoint

Thesizeoftheseobjectsisalsomachine-dependent.Therearealsoarrays,structuresandunionsofthesebasictypes,pointerstothem,andfunctionsthatreturnthem,allofwhichwewillmeetinduecourse.

Computationinthetemperatureconversionprogrambeginswiththeassignmentstatements

whichsetthevariablestotheirinitialvalues.Individualstatementsareterminatedbysemicolons.

Eachlineofthetableiscomputedthesameway,soweusealoopthatrepeatsonceperoutputline;

thisisthepurposeofthewhileloop

...

Thewhileloopoperatesasfollows:

Theconditioninparenthesesistested.Ifitistrue（fahrislessthanorequaltoupper）,thebodyoftheloop（thethreestatementsenclosedinbraces）isexecuted.Thentheconditionisre-tested,andiftrue,thebodyisexecutedagain.Whenthetestbecomesfalse（fahrexceedsupper）theloopends,andexecutioncontinuesatthestatementthatfollowstheloop.Therearenofurtherstatementsinthisprogram,soitterminates.

Thebodyofawhilecanbeoneormorestatementsenclosedinbraces,asinthetemperatureconverter,orasinglestatementwithoutbraces,asin

while（i<

j）

i=2*i;

Ineithercase,wewillalwaysindentthestatementscontrolledbythewhilebyonetabstop（whichwehaveshownasfourspaces）soyoucanseeataglancewhichstatementsareinsidetheloop.Theindentationemphasizesthelogicalstructureoftheprogram.AlthoughCompilersdonotcareabouthowaprogramlooks,properindentationandspacingarecriticalinmakingprogramseasyf