Chapter9StructuresFangWangOutlines9.1StructureVariables9.2Structurename9.3ArraysandStructures29.1StructureVariablesStructuresareawaytogroupseveralrelatedvariablesintooneplace.Eachvariableinthestructureisknownasamemberofthestructure.Unlikeanarray,astructurecancontainmanydifferentdatatypes(int,float,char,etc.).Thepropertiesofastructurearedifferentfromthoseofanarray.Theelementsofastructure(itsmembers)aren’trequiredtohavethesametype.Themembersofastructurehavenames;toselectaparticularmember,wespecifyitsname,notitsposition.39.1StructureVariablesDeclaringStructureVariablesAstructureisalogicalchoiceforstoringacollectionofrelateddataitems.Adeclarationoftwostructurevariablesthatstoreinformationaboutstudents: structstudent{ intnumber; charname[25]; intage; }49.1StructureVariablesDeclaringStructureVariablesAbstractrepresentationsofastructure:Membervalueswillgointheboxeslater.5agestructstudent{ intnumber; charname[25]; intage; }Mike;structstudent{ intnumber; charname[25]; intage; };structstudent

Mike;struct{ intnumber; charname[25]; intage; }Mike;Structure1.Thestructureisdesignedbyusersthemselves;2.Itiscomposedofseveraldifferentbasicdatatypes;3.ItisadatatypeofC,whichisequivalenttointordoubletypes.69.1StructureVariablesDeclaringStructureVariablesThemembersofastructurearestoredinmemoryintheorderinwhichthey’redeclared.AppearanceofMikeAssumptions:Mikeislocatedataddress2000.Integersoccupyfourbytes.NAMEoccupies25bytes.Therearenogapsbetweenthemembers.7age9.1StructureVariablesInitializingStructureVariablesAstructuredeclarationmayincludeaninitializer: structstudent{ intnumber; charname[25]; intage; }Mike={202201,"MikePatrick",10}, Tom={202202,"TomdaVinci",15};AppearanceofMike

afterinitialization:8age202201MikePatrickage202202TomdaVinci159.1StructureVariablesOperationsonStructures--------name.memberToaccessamemberwithinastructure,wewritethenameofthestructurefirst,thenaperiod,thenthenameofthemember.StatementsthatdisplaythevaluesofMike’smembers: printf("number:

%d\n",

Mike.number); printf("name:

%s\n",

Mike.name); printf(“%d%s%d\n",

Tom.number,Tom.name,Tom.age);

202202TomdaVinci15

99.1StructureVariablesOperationsonStructuresThemembersofastructurearelvalues.Theycanappearontheleftsideofanassignmentorastheoperandinanincrementordecrementexpression:

Tom.number=258;

/*changesTom'snumber*/ Tom.age++;

/*incrementsTom'sage*/109.1StructureVariablesOperationsonStructuresTheperiodusedtoaccessastructurememberisactuallyaCoperator.Ittakesprecedence

overnearlyallotheroperators.Example:

scanf("%d",&Tom.age);

The.operatortakesprecedenceoverthe&operator,so&computestheaddressofTom.age.119.1StructureVariablesOperationsonStructuresTheothermajorstructureoperationisassignment:

Tom=Mike;TheeffectofthisstatementistocopyMike.numberintoTom.number,MintoT,andsoon.129.2StructurenameSupposethataprogramneedstodeclareseveralstructurevariableswithidenticalmembers.Weneedaname(“structuretag”)thatrepresentsastructure.139.2StructurenameDeclaringaStructureTagAstructuretagisanameusedtoidentifyaparticularkindofstructure.Thedeclarationofastructuretagnamedteacher: structteacher{ intnumber; charname[25]; charcourse[50]; };Notethatasemicolonmustfollowtherightbrace.149.2StructurenameDeclaringaStructureTagTheteacher

tagcanbeusedtodeclarevariables:

structteachert1,t2;Wecan’tdropthewordstruct:

teachert1,t2;/***WRONG***/

teacher

isn’tatypename;withoutthewordstruct,itismeaningless.159.2StructurenameDeclaringaStructureTagThedeclarationofastructuretagcanbecombinedwiththedeclarationofstructurevariables: structpart{ intnumber; charname[25]; inton_hand; }part1,part2;169.2StructureTypesDeclaringaStructureTagAllstructuresdeclaredtohavetypestruct

part

arecompatiblewithoneanother:

structpartpart1={528,"Diskdrive",10};

structpartpart2; part2=part1;

/*

legal;

both

parts

have

the

same

type

*/17Classassignment41:StructureCreateastructurecalledmyCountry#include<string.h>18structmyCountry//CreateastructurecalledmyCountry{charname[20];charlanguage[10];charlocation[10];intpopulation_billion;charunique_feature[100];};intmain(){//DeclareastructurevariableofmyCountrycalledChina

structmyCountryChina;strcpy(C,“P.R.China”);//AssignvaluestomembersofChinastrcpy(China.language,“Chinese”);strcpy(China.location,“Asia”);China.population_billion=14;strcpy(China.unique_feature,“Panda”);//Printvaluesprintf("%s\n%s\n%s\n%d\n%s\n",C,China.language,China.location,China.population_billion,China.unique_feature);return0;}9.2StructurenameStructuresasArgumentsandReturnValuesFunctionsmayhavestructuresasargumentsandreturnvalues.Afunctionwithastructureargument: voidprint_part(structpartp) { printf("Partnumber:%d\n",p.number); printf("Partname:%s\n",); printf("Quantityonhand:%d\n",p.on_hand); }Acallofprint_part: print_part(part1);199.2StructurenameStructuresasArgumentsandReturnValuesAfunctionthatreturnsapartstructure: structpartbuild_part(intnumber, constchar*name, inton_hand) { structpartp;

p.number=number; strcpy(,name); p.on_hand=on_hand; returnp; }Acallofbuild_part:

part1=build_part(528,"Diskdrive",10);209.3ArraysandStructuresArraysofStructuresThiskindofarraycanserveasasimpledatabase.Anarrayofpartstructurescapableofstoringinformationabout100parts:

structpartinventory[100];//庫存零件100個219.3ArraysandStructuresArraysofStructuresAccessingapartinthearrayisdonebyusingsubscripting:

inventory[i]Accessingamemberwithinapartstructurerequiresacombinationofsubscriptingandmemberselection:

inventory[i].number=883;Accessinga