大二上復習最終完美版匯編-08

Chapter8Processingstringdata處理串數(shù)據(jù)Textbook:11Processingstringdata8086SymbolicinstructionsAlistofthesymbolicinstructionsfortheIntelprocessorfamilyarrangedbycategory.①DataTransfer

數(shù)據(jù)傳送類指令②ArithmeticandLogical算術、邏輯運算類指令③BitShifting

位操作類指令④StringOperation

串操作類指令⑤Transfer(ConditionalandUnconditional)控制轉移類指令⑥ProcessorControl

處理機控制類指令Processingstringdata處理串數(shù)據(jù)7.1Textbook:11ProcessingstringdataoutlineREP:

repeatstringprefix

（重復前綴）MOVS: movestring

LODS: loadstringSTOS: StorestringCMPS:

Comparesbyte,wordordouble-wordlocations.SCAS:

ComparesthecontentsoftheAL,AX,orEAXwiththecontentsofamemorylocation.INS: TransfersabytefromporttomemoryOUTS: Transfersabytefrommemorytoport.MOVinstruction(move)TheMOVinstructiontransfers(orcopies)data

referencedbytheaddressinthesecondoperandtotheaddressinthefirstoperand.Format:從源操作數(shù)地址把一個字節(jié)、字或雙字復制到目的操作數(shù)地址,存放在源地址的值不會改變。比如C語言中賦值語句intcount=0;[label:]MOVreg/mem,reg/mem/imm;reg/mem←reg/mem/immValidMOVOperationsByteflddb?;DefineabyteWordflddb?;Defineaword1)RegisterMovesmovdx,cx;register-to-registermoves,ax;register-to-segmentregistermovbytefld,dh;Register-to-memory,directmov[bx],al;register-to-memory,indirectExamplesFeaturesofstringoperationsAstringinstructioncanspecifytherepetitiveprocessingbyte,word,ordouble-wordatatime.串操作指令可以指定每次以字節(jié)/字/雙字的形式操作。(Featuresofstringoperations)ForthestringinstructionsMOVS,STOS,CMPS,andSCAS,besurethatyour.EXEprogramsinitializetheESregister.ESregisterusually,butnotnecessarily,withthesameaddressasthatintheDSregister:

使用串操作指令MOVS/STOS/CMPS/SCAS時，需要初始化ES寄存器。ES常與DS有相同的值。(Featuresofstringoperations)ESregisterusually,butnotnecessarily,withthesameaddressasthatintheDSregister:

MOVAX,@data;getaddressofdatasegmentMOVDS,AX

;storeitinDSMOVES,AX;andinES簡化段定義中給ES賦值實例，完整段定義中？Examples(Featuresofstringoperations)ForstringinstructionsusethesuffixesB,W,andDforhandlingbyte,word,ordouble-wordstring.串操作指令可以使用后綴B/W/D來表示字節(jié)/字/雙字操作。(Featuresofstringoperations)Therearebasicallytwowaystocodestringinstructions:

(兩種串操作編程方式)Wherethedefinitionoftheoperandsindicatesthelength

(通過操作數(shù)的長度定義)

Codetheinstructionwithoutoperands(無操作數(shù))LEADI,BYTE2

;addressofbyte2LEASI,byte1;addressofbyte1MOVSB

;movebyte2tobyte1MOVSbyte1,byte2Examples(Featuresofstringoperations)REPrepeatstringprefix7.2REP:repeatstringprefixTheREPprefiximmediatelybeforeastringinstruction(anystring-instructionexceptingLOADS)providesforrepeatedexecutionbasedonaninitialcountthatyousetintheCXregister.

Format:REPstring-primitive

Suchas:REPMOVSBREP的位置：在除LOADS的其它串指令之前，重復操作次數(shù)由CX值確定。REP:repeatstringprefixREPexecutesthestringinstructionCXCX-1,and

repeatsthisoperationuntilCX=0.REP功能：每執(zhí)行一次串操作，CX<-CX-1，直至CX=0Prepare:SISourcestringfirstaddress(orendaddress)源串首地址DIDestinationstringfirstaddress

(orendaddress)

目的串首地址CXString-lengthcount串長度Setdirectionflag(D).傳送方向(REP:repeatstringprefix)使用REP時的預備工作(REP:repeatstringprefix)DirectionflagD:Determinesthedirectionofarepeatedoperation. Justusedinstringinstruction;

MakeDI、SI:auto-increment(增)

when

(D=0)

or

auto-decrement

(減)

when(D=1)方向標志D用于確定操作的方向，在串操作中使DI/SI自動遞增或遞減。(REP:repeatstringprefix)2Directionflagcontrolinstruction：

CLD

ClearDirectionflagD（D=0)Selectauto-increment

STD

SetDirectionflagD（D=1)Selectauto-decrementDATASTR1DB25DUP(‘*’);sendingfieldDATASTR2DB25DUP(‘‘);receivingfield…CLD;cleardirectionflagMOVCX,25;initializefor25byteLEADI,DATASTR2;initializereceivingLEASI,DATASTR1;initializesendingaddress

REPMOVSB;copydatastr1todatastr2Equivalent:L1:MOVAX,[SI];getbytefromDATASTR1MOV[DI],AX;storebyteinDATASTR2INCSI;incrementfornextbyteINCDILOOPL1;decrementCXandrepeatExamples:REP使用例程1定義方向2定義傳送數(shù)量3定義源/目的串偏移量4串操作指令Examples(REP:repeatstringprefix)REPRepeatoperation,untilCX=0.REPE/REPZ

Repeatwhileequal/zero,

Stopwhennotequal/zero

or

CX=0.REPNE/REPNZ

Repeatwhilenotequal/zero,

Stopwhenequal/zero

or

CX=0.MOVS7.4MOVS:movestringinstructionMOVS;memorymemoryES:[DI]byte,word,double-word(DS:[SI])

+or–DIandSI

,dependingondirectionflagD(MOVS:movestringinstruction)MOVSLODS7.4LODS:loadstringinstructionLODS;AL(orAX,orEAX)memory

;(AL)

/(AX)/(EAX)(DS:[SI])

(noteffectDI,notuseREP)功能：將內(nèi)存單元的數(shù)據(jù)放入AL/AX中，不涉及DI，不使用REP(LODS:loadstringinstruction)(LODS:loadstringinstruction)DataSegmentFigure12-LODSWinstructionoperation(D=0)STOS7.5STOS:StorestringinstructionSTOS;memoryAL(orAX,orEAX);(ES:[DI]) (AL)

/(AX)/(EAX)

(noteffectSI)功能：將AL/AX的數(shù)據(jù)放入內(nèi)存單元中，不涉及SI(STOS:Storestringinstruction)(STOS:Storestringinstruction)CMPS7.6CMPS:ComparestringinstructionComparesbyte,wordordouble-wordmemorylocations.memorymemory (DS:[SI])) (ES:[DI])+or–DIandSI

,dependingondirectionflagD.TosetA,C,O,P,S,andZflags.比較一段內(nèi)存單元的內(nèi)容

(DS:[SI])<->(ES: