c語言上課筆記2（Cclassnotes2）

c語言上課筆記2(Cclassnotes2)Constantdefinition:#defineconstantnameconstantvalueNotedefinesconstantsyntaxwithoutsemicolons(()),usuallydefiningconstantsontheheaderofthesource(togetherwith#include)Cases:#definePI3.14Printf(N=%d,M=%f,N,M);//printf("N=%d,M=%f,3,3.14);//(mainlycompletedareplacementfunction)Variabledefinition:Grammar:datatypevariablename[=value]Intnumber;//defineavariablenumberIntnumber2-20//defineavariablenumber2andassignittotheinitialvalueis20Number=10;//the10assignmentofthevariablenumberThesecondmethoddefines:int,Number1,number2=20,number3=10;Printf(/，number2=%dnumber3=%d\n,number2",number3");%dstandsforastationsymbol,whichisonlyanintegerdataThefirst%dcorrespondstothenumber2Thesecond%dcorrespondstothenumber3Namingrulesforvariables(identifiers):Thevariablenamecancontainletters,numbersand_(underlined)assemblyThevariablenamecannotcontainanyspecialcharacters,suchas:outsideexcept#,comma,space,etc.Thevariablenamemustbealphabeticor_(underlined)atthebeginningVariablenamescannotcontainwhitespacecharacters(newlinecharacters,spaces,andtabs)calledwhitespacecharactersCertainwordsintheClanguage(suchasdoubleandfloat)arecalledreservedwords,whichhavespecialmeaningsandcannotbeusedasvariablenamesTheClanguageiscasesensitive,sothevariablepriceandthevariablePRICEaretwodifferentvariablesNote:1.variablename,knowitsname,knowitsmeaning2.$canbeusedShort16bitOnethousandtwohundredandthirty-fourtrillionandfivehundredandsixty-sevenbillioneighthundredandninetymilliononehundredandtwenty-threethousandfourhundredandfifty-sixOnethousandonehundredandonetrillionandtenbilliononehundredmilliononehundredandonethousandandtenBinarydecimalsystem000000000000000000000000000000001100000000000000102OnethousandonehundredandeleventrillionandonehundredandelevenbilliononehundredandelevenmilliononehundredandeleventhousandonehundredandelevenFloatfl=3.1345f;//32Doublef2=3333.4;//64Integerdata:Short2bytesInt4bytesFloating-pointdata:Float4bytesDouble8bytesCharacterdata:Char1bytesTheunitofcomputerrepresentationis1024ascarry(usually1000)1bytes(byte),8bits,00000000111111111KB=1O24bytes1MB=1024KB1GB=1024MB1TB=1024GBCharactertype:charCharacterliteral:‘0','A'B',Han'(wrong.AsinChinese,incomputerisexpressedin2bytes)a97'A'65Arithmeticoperation:?一?Twooperandisanintegerdivisor,note:integerdivisoranddividendsymbolsthesameresultispositive,negativereturnThe%twooperandcanonlybeanintegerdivisor.TheremaindernoteistheresultofthesignedsymbolSincetheincrease++1cases:n=20;n++;〃n++andn=n+Iequivalent-minus1Note:(n+30)++;errorOnlyreferstothevariable-++(++-preandpost)Sum=n++;//postaddsum=n;n=n+l;Sum=++n;//prefixincrementn=n+l;sum=n;Cases:Intx=2;Floaty-5;Floats;S=y/x;〃y=y+x;Printf s);Assignmentoperation:=assigntheresultoftheexpressionontherighttotheleftvariable//n=n+40=n+=40;*-AverageRelationaloperator:(theresultofthecalculationisalogicalvalue,trueorfalse)<二==notequalto==equalNote:intheClanguage,A’〇"meansAfalse","non0"meanstrueLogicaloperator:Andwhenthetwologicandshortcircuitconditionsistrue,theresultsaretruemultiplicationprocessingshortcircuitlogicoraslongasaconditionistrue,theresultisreallyadditiveItistruethatthelogicisnottakenandthereverseisfalse,andthefalsenegationistrue011000110010andtheequivalentofmultiplicationTheequivalentof0121||additionSum=(5II(>2)(n++)>0);and//1|saidshortcircuitoroperationWhatisashortcircuitand/or:whentheexpressionontheleftiscalculatedandtheresultoftheentireexpressioncanbedetermined,theexpressionontherightisnolongercomputedExample:dataisreceivedfromthekeyboardttinclude<stdio.h>ttinclude<stdlib.h>Void,main(){Intn;Floatm;Intx;Printf(enterthevalueofN:\n);Scanf(%d,&n);//receiveinputfromthekeyboardvaluePrintf(enterthevalueofM:\n);Scanf("%f",&m);Amemorymap:728placeThreethousandfivehundredandseventy-threeThreethousandfivehundredandseventy-fourThreethousandfivehundredandseventy-fiveThreethousandfivehundredandseventy-six357703578035790inti;358030i=30;00009&i00010000110001300014000150001600017000180001900020000210002200023000240002500026Address4GAssignment:

discountthebook,sellathalfprice,printtheoriginalpriceofthebook,andthenprintthebookpriceishalfpricefromthekeyboardinputa5bitinteger,printoutputbits,ten,100,thousand,10000,suchas:54352bitsfor2,tenfor500,3for1000,5for4entertheradiusofacirclefromthekeyboard,calculatetheareaofthecircleandoutputtheresultentertheradiusandheightofacylinderfromthekeyboard,calculatethevolumeofthecylinder,andoutputtheresultSizeofoperator:Syntax:sizeof(datatype)sizeof(variable)Sizeof(float)sizeof(x)例.intx=20.shorts(m=20.floatf;doubled;charc;printf('%d”,sizeof((c)).printf和scanf是格式輸出輸入語句printf(格式字符串,參數(shù).參數(shù)n).scanf(格式字符串,地址L地址n);and-＞取變量a的內(nèi)存地址printf("xxxxx");轉(zhuǎn)義字符\n\tthe\\(2)例:printf("thecheckingforexistence:d:\\testl.exe\").從鍵盤上接上數(shù)據(jù).注:1.scanf語句中的格式字符中盡量不要除%d%f%Id%If這些占位符之外的其它字符特別小心不要加上、n.接收數(shù)據(jù)是存放在ー個(gè)內(nèi)地址里面變量名必須加上&.接收數(shù)據(jù)以空格或換行等分隔(%c他可以接收空格和換行)scanf(%d%d\n\n”,x,m);getchar從鍵盤上讀取ー個(gè)字符可以接收鍵盤上任意字符()例:cahrx=getchar().fflush(stdin);/Z清空輸入緩沖區(qū)putchar把ー個(gè)字符型變量輸出到屏幕上去(變量名)例:putchar(x).注getcharputcahr只對(duì)針對(duì)字符數(shù)據(jù)處理.'\n''an'\032"a'""二級(jí)考試都是表示是ー個(gè)字符.選擇語句.單分支當(dāng)條件表達(dá)式為真時(shí)執(zhí)行語句!,反之不執(zhí)行語法:if(條件表達(dá)式)語句!.例.intx=20,30.if(x)(y){printf(by\n");)特殊用法.if(0)(printf("xxxxx");)雙分支:當(dāng)條件表達(dá)式為真是執(zhí)行語句1,反之執(zhí)行語句2.if（條件表達(dá)式）語句!.else(語句2.)注:1.if語句中{}{}里面可以有零條或多條語句表示代表塊.2.當(dāng){}{}可以省略掉只有一個(gè)條語句時(shí).例.intx=70,y=30;if(x)(y)!printf(x>y").printf(x>y").printf(x>y").elseprintf(">").)多分支ー種使用if語嵌套2種switch語句.if(條件表達(dá)式DIif(條件表達(dá)式2){語句!.)else語句2.elseStatement2;Thenestingofaifstatementistheexecutionofaifstatement.ThestatementofthecodeblockisnotaifstatementCases:ttinclude<stdio.h>Void,main()//betweenstudentachievementstatistics90-100-89-80excellent70good 79in60--69latticeisnotverycellInts;Printf〈pleaseenterastudent,sscore:，z);Scanf("/d",&s);//79If(s>=0ands<=100)If(s=90)Printf(“90to100betweengood");Else//0—89If(s>=80)Printf(80-89good);Else//0—79If(s>=70)Printf("70一一79");Else//0-69If(s>=60)Printf(pass);Else//059Printf("fail");ElsePrintf("thestudentsyouenteredincorrectly."!!");6000tax:(60003500-socialsecurity)*10%105switchStatementsThecomputingformula,whentheexpressionresultswithconstantequaltoexecutethestatementfollowingthebreakstatement,untilImet;orholdaswitchstatementbeforefinallyoutoftheentireswitchstatement;ifatallcasestatementscannotfindthesameconstant,thenthelinefollowingthedefalultstatementSwitch(expression)Caseconstant1:Sentence;Break;Caseconstant2:Sentence;Break;Default:Sentence;Break;)break;jumpoutofcurrentswitchexpressionscanonlybestoredinmemory,whichareintegers(char,bool,int),andfloatingpointtypescannotbeusedCases:ttinclude<stdio.h>ttinclude<stdbool.h>//addthecorrespondingheaderVoid,main()Charx;Switch(x){Default:Printf("nocorrespondingvalue");Break;Case'a':Printf("youentered1");//break;Case'b';Printf("youentered2");//break;Case99:Printf("youentered3");//break;Case4:Printf("youentered4");//break;Multiplechoicestatements:ifstatementsnested,switchstatementstwotocompleteCompare:Typically,switchstatementsareusedwhenhandlingafixedvalueTheifstatementisusuallyusedwhendealingwiththevalueofanintervalsegmentLoopstatement:whiledo...WhileforSyntax:For(initialvalue);Condition;steplength)Loopbodystatement;)Initialvalue:initializationasaloopCondition:theloopbodyexecuteswhentheconditionistrueStepsize:addseveralcountsatatimeNote:theinitialvalueandsteplengthcanbeomitted,buttheloopconditionmustbewrittenoutWhentheloopconditionisalwaystrue,itisdead,andinrealprocessdevelopment,itsometimesusesadeadloopFor((1;)i)Cases:Void,main()Inti;//asacounterFor(i=l;iく=360;i++)(Printf(%d,\n,I);))Dowhilesyntax:Do(Loopbody;}while(condition);Whentheconditionistrue,theloopbodyisexecuted,regardlessofthecondition,andtheloopbodyisexecutedVoid,main()Intsum=O;//statisticsyoupaymemymoneyDoPrintf(hitsyoua\n);Sum=sum+100;//moneyWhile(sum<1000);Whilesyntax:Whentheconditionistrue,theloopbodyisexecuted,theconditionisfirstjudged,andthentheloopbodyisdeterminedWhile(condition)Loopbody:Cases:Void,main()Intsum=0;//statisticsyoupaymemymoneyWhile(sum<1000)(Printf("sendsomeone,paythemoney,orkillyou,\n!");Sum=sum+100;))Homework:choosedocomprehensiveproblemsoffreshman:inputfromthekeyboardbycycle(numberunknown)Cprogramdesignthiscoursescore,totalscoreandscorestatistics,whentheinputisnegative,thestopinputstatistics,finally,printoutthetotalscore,thetotalnumberofstatistics,andtheaveragescore#include<stdio.h>(main)Thestatisticalresultsof/Floatsum=0;//totalscorestatisticsIntcount=l;//thenumberofStatisticsFloatave=0;//averageFloatm;Printf("pleaseenter%dstudent'sscore:",count);Scanf(%f,&m);//enteraresultWhile(m>=0){//statisticsSum=sum+m;Count++;Printf("pleaseenter%dstudent'sscore:",count);Scanf(%f,&m);//enteraresultCount—;//theactualnumberofstudentsAve=sum/count;Printf(thetotalscoreis%f,thenumberofstudentsis:%d,theaveragescoreis:%f,sum,count,ave);Continue;//whenperformingcontinuesaidtheendofthecycle,continuetoimplementthenextcycleWhen/afterthecontinue,thecontinueloopstatementisnotexecuted(thiscycle)Note:continuecanonlybeusedinloopstatementsBreak;Whenthebreakstatementisexecuted,itmeansexitingtheentireloop,Note:usedinswitchstatementsandloopstatementsSummary:comparisonofthethreemajorcyclesThewhilefirstdeterminesthattheexecutionisusuallyusedinthecaseofanindefinitenumberofloops,andthatitisimpossibletoexecutetheloopatonetimeThedowhileexecutesfirstandthenjudges,usuallyusingtheloopbodyatleastonceintheuncertainnumberofcyclesForfirstjudgeandthenexecute,usuallyinthecaseofdeterminingthenumberofcycles,andmaynotexecutetheloopatonetimeLoopnesting:NestedanotherloopwithintheloopbodyCases:ttinclude<stdio.h>(main){*AtAtAtResult*/Intj;For(i=l;iく=4;i++)For(i=l;iく=4;i++)For(j=l；jく=9;j++)Printf(*);Printf("\n");//printeachline,line^include<stdio.h>(main)Printf(*);Printf("\n");//printeachline,line^include<stdio.h>(main)AtAtAtResult*/Inti;Intj;1=1；While(i<=4)//cycle{J=l；While(j<=9)Printf(*);J++；***Array:usedtostoremorethanoneelementIntSI,S2,S3//storageofthreegradestudentsIntx[100];//defineanarraytostoreonehundredstudentachievementDefininganarray:AnarrayisacollectionofthesamedatatypeSyntaxformat:datatype,arrayname[numberofelements]Thedatatypeofthearrayname[]={value1,avalueof2.Thevalueofn}//...AndgivehimthedefinitionofanarrayinitializationTodefineanarray,intdefaultsto0,thefloatingpointtypeis0.OF,andchardefaultsto＜、〇'Cases:Floats[5];//arraydefinitionfiveelementsizeoffloat,whichcanonlybeinstalledfloattypevalueisequivalenttothedefinitionofthe5variablesoftypefloatCharch[20];Atthesametimetheinitialarray//definearraysInta[10]={l,2,3,4,5,6,7,8,9,0};Ints[]={l,2,3,4,5,6,7,8,9,0};Ints2[20]={};Arrayaccess:Thearrayname[subscriptN]'meanstheelementaccessingthesubscriptNAccessthefirstelementarrayname[0]Accessthesecondelementarrayname[1]Note:thesubscriptofanarraybeginsat0andcannotbecrossedwhenaccessing//arrayttinclude<stdio.h>Void,main()Ints[5];10//SdefinesanarrayofstudentachievementIntsum=0;For(i=0;iく=4;i++)!Printf〈enterthevalueofthefirst%delement”:i+1");Scanf("%d",&s[i]);)For(i=0;iく=4;i++)Sum=sum+s[i];Printf("%d",sum);)Two-dimensionalarray:Syntax:Thedatatypeofthearrayname[ロ]thenumberofrowsofcolumns;Thedatatypeofthearrayname[linenumberN][columnnumberM]=turningvalue1,2..ValueM},...{}}..;Note:whenatwo-dimensionalarrayisdefined,therowindexcanbeomittedandcolumnindexshouldnotbeomittedForexample:ints[3][3];//defineatwo-dimensionalarrayofthreerowsandthreecolumnscolumnLine000102101112202122Visit:row,columnarrayname[].S[0][0]accesseselementsfromrowstocolumnsS[2][2]accessesthreerowsofthreecolumnelementsExample:s[〇][0]=20;S[0][l]=30;Intarray[3][4];//defineanarray//initializeArray[0][0]=lll;//thefirstlineinitializationArray[0][1]=111;Array[〇][2]=111;Array[0][3]=111;Array[1][0]=lll;//initializesecondArray[1][1]=111;Array[1][2]=111;Array[1][3]=111;Array[2][0]=lll;//initializethirdArray[2][1]=111;Array[2][2]=111;Array[2][3]=111;Secondmethodsforaccessingtwo-dimensionalarrays:Intarray[3][4];//defineanarray/arraynamerowcolumnindex[]ロInt,I,j;For(i=0;i<3;i++)(For(j=0;j<4;j++)Array[i][j]=20;Printf("\n");)Stringsaredouble-citedExample:〃ABCD","LDG"Note:tobeseparatedfromcharacterconstants,(a'\n'Cdoesnothavestringdatatypes,butusesthechararraytosto