大二上复习最终完美版汇编-08

Chapter8Processingstringdata处理串数据Textbook:11Processingstringdata8086SymbolicinstructionsAlistofthesymbolicinstructionsfortheIntelprocessorfamilyarrangedbycategory.①DataTransfer

数据传送类指令②ArithmeticandLogical算术、逻辑运算类指令③BitShifting

位操作类指令④StringOperation

串操作类指令⑤Transfer(ConditionalandUnconditional)控制转移类指令⑥ProcessorControl

处理机控制类指令Processingstringdata处理串数据7.1Textbook:11ProcessingstringdataoutlineREP:

repeatstringprefix

（重复前缀）MOVS: movestring

LODS: loadstringSTOS: StorestringCMPS:

Comparesbyte,wordordouble-wordlocations.SCAS:

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

referencedbytheaddressinthesecondoperandtotheaddressinthefirstoperand.Format:从源操作数地址把一个字节、字或双字复制到目的操作数地址,存放在源地址的值不会改变。比如C语言中赋值语句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节/字/双字的形式操作。(Featuresofstringoperations)ForthestringinstructionsMOVS,STOS,CMPS,andSCAS,besurethatyour.EXEprogramsinitializetheESregister.ESregisterusually,butnotnecessarily,withthesameaddressasthatintheDSregister:

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

MOVAX,@data;getaddressofdatasegmentMOVDS,AX

;storeitinDSMOVES,AX;andinES简化段定义中给ES赋值实例，完整段定义中？Examples(Featuresofstringoperations)ForstringinstructionsusethesuffixesB,W,andDforhandlingbyte,word,ordouble-wordstring.串操作指令可以使用后缀B/W/D来表示字节/字/双字操作。(Featuresofstringoperations)Therearebasicallytwowaystocodestringinstructions:

(两种串操作编程方式)Wherethedefinitionoftheoperandsindicatesthelength

(通过操作数的长度定义)

Codetheinstructionwithoutoperands(无操作数)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，重复操作次数由CX值确定。REP:repeatstringprefixREPexecutesthestringinstructionCXCX-1,and

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

(orendaddress)

目的串首地址CXString-lengthcount串长度Setdirectionflag(D).传送方向(REP:repeatstringprefix)使用REP时的预备工作(REP:repeatstringprefix)DirectionflagD:Determinesthedirectionofarepeatedoperation. Justusedinstringinstruction;

MakeDI、SI:auto-increment(增)

when

(D=0)

or

auto-decrement

(减)

when(D=1)方向标志D用于确定操作的方向，在串操作中使DI/SI自动递增或递减。(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定义方向2定义传送数量3定义源/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：将内存单元的数据放入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：将AL/AX的数据放入内存单元中，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.比较一段内存单元的内容

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