第7章 微处理器程序设计

CHAPTER7ProgrammingtheMicroprocessor

(第7章微处理器程序设计)(P.217)MachineLanguageandAssemblyLanguage

(机器语言和汇编语言)(P.105)Machinelanguageisthenativebinarycodethatthemicroprocessorunderstandsandusesasitsinstructiontocontrolitsoperation.Anobjectprogramiswritteninmachinelanguage.Assemblylanguageisasymbolicprogramminglanguage.Anassemblysourceprogramiswritteninassemblylanguage.Example AssemblyLanguage:ADDAL,2MachineLanguage:0000010000000010TheAssembler

(汇编程序)(P.218)Theassemblerprogramconvertsasymbolicsourcemodule(assemblysourceprogram)intoahexadecimalobjectfile.Therearetwoassembleroftenusedbythe8086/8088microprocessor.OneisASM-86,andanotherisMASM-86macroassemblerprogram.assemblysourceprogramAssemblerobjectprogramProgrammingthe8086/8088Microprocessor

(8086/8088汇编语言源程序开发)Toprogrammingthe8086/8088microprocessor,anassemblysourceprogramisgenerated,assembled,linkedanddebuggedintheMSDOSorPCDOSoperatingsystem.Therearetwoprogrammingforms.MemorymodelsFull-segmentdescriptionsMemorymodels

(存储模型)(P.776)ModelTypeDescriptionTinyAlldataandcodemustfitintoonecodesegment.SmallThismodelcontainstwosegments:onedatasegmentof64Kbytesandonecodesegmentof64Kbytes.MediumThismodelcontainsonedatasegmentof64Kbytesandanynumberofcodesegmentsforlargeprograms.CompactOnecodesegmentcontaintheprogram,andanynumberofdatasegmentscontainthedata.LargeThelargemodelallowsanynumberofcodeanddatasegments.STOSDATA4ES:[DI]=EAX;DI=DI+4(ifDATA4isadoubleword)TABLEA-1MemorymodelsfortheassemblerEXAMPLEA-4

.MODEL SMALL .STACK 100H .DATA FROG DB 10 DATA1 DB 100DUP(2) .CODEBEGIN: MOV AX,DGROUP MOV DS,AX ………. END BEGINFull-segmentdescriptions

(完整的段描述)EXAMPLE： DATA SEGMENT DATA1DB0F8H,60H,0ACH,74H,3BH DATA2DB0C1H,36H,9EH,0D5H,20H DATAENDS CODESEGMENT ASSUMECS:CODE,DS:DATA START:MOVAX,DATA MOVDS,AX …….. CODEENDSENDSTARTCharacteristics

(汇编语言源程序的特点)Anassemblysourceprogramcontainssomesegments.AsegmentisdefinedwithSEGMENT/ENDS.Anassemblysourceprogramiscomposedofagroupofassemblystatements.Anassemblystatementiswritteninaline.TheassemblysourceprogramisendedwithENDdirective.Formatofanassemblystatement

(汇编语言语句的组成)Therearetwokindofinstructions.DirectivestatementInstructionstatementDirectivestatement

(指示性语句)Format:VariablenameDirectiveOperand;NotationNoteAfterandirectivestatementisassembled,thereisnoobjectcodesgeneratedanditisnotexecutedbythemicroprocessor.Whenandirectivestatementisassembled,itallocatedmemorylocationsforthedataThenotationisprefixedwithasemicolon.Instructionstatement

(指令性语句)FormatLabel：InstructionopcodeOperand;NotationNoteAninstructionstatementisconvertedintoobjectcodebyanassemblerandisexecutedbythemicroprocessor.Alabelisfollowedwithacolon.ElementsofAssemblyLanguage

(汇编语言的基本元素)TheelementsoftheassemblylanguagearesymbolicaddressInstructionopcodeDirectiveOperandNotationsymbolicaddress

(符号地址)VariableAvariableisthenameofseveralmemorylocationsthatstorethedata.Itrepresentsthestartingaddressofthesememorylocations.Avariableisusuallylocatedindatasegment.Itcanalsolocatedinothersegment,forexample,theextrasegment.Avariablecanbedefinedasbyte-sized,word-sizedordoubleword-sizedbythedirectives.LabelAlabelrepresentsthestartingaddressofaninstruction.Alabelcanbedefinedasneartype(bydefault)orfartypebythedirective.InstructionOpcodeandDirective

(指令操作码和伪指令)AinstructionopcoderepresentstheoperationofaninstructionsuchasMOVandADD.DirectivessuchasDBandDWareisnotexecutedbythemicroprocessor.Thereare20directiveinASM-86.VariableDefinitionDirectivesSymbolEvaluationDirectivesDataTypeDefinitionDirectivesSegmentDefinitionDirectivesProcedureDefinitionDirectivesAssemblySourceEndDirectivesVariableDefinitionDirectives

(数据定义伪指令)DBFormat:Variablename DBOperand[,Operand]Thisdirectiveallocatememorylocationsforthebyte-sizedoperands.Thestartingaddressissymbolizedbythevariablename.Theoperandscanbeimmediate,formula,ASCII,?orDUPformula.DWFormat:Variablename DWOperand[,Operand]Thisdirectiveallocatememorylocationsfortheword-sizedoperands.Thestartingaddressissymbolizedbythevariablename.Theoperandscanbeimmediate,formula,ASCII,?orDUPformula.DBFormat:Variablename DDOperand[,Operand]Thisdirectiveallocatememorylocationsforthedoubleword-sizedoperands.Thestartingaddressissymbolizedbythevariablename.Theoperandscanbeimmediate,formula,ASCII,?orDUPformula.Example

;Assumethedatasegmentaddressis0A0CH DATA SEGMENT ;datasegmentnamedDATAstarts.0000H41H,42H,0DH,0AH BUF DB

‘AB’,0DH,0A0004H00H,00H A DW BUF0006HAAH,FFH B DW 0FFAAH0008H00H,00H,0CH,0AH C DD BUF000CH02H,42H,02H,42H M DB 2DUP(2,‘B’)0010H31H,32H,01H,02H DB ‘12’,1,2

DATA ENDS ;datasegmentend.SymbolEvaluationDirectives

(符号赋值伪指令)Formatsymbolname EQU formulaExample CREQU40H ADREQUABC ADREQUCXDataTypeDefinitionDirectives

(定义存储单元类型伪指令)ThedirectivesBYTEPTR,WORDPTRandDWORDPTRcanbeappendedtoaninstructiontospecifythetypeofthememorylocation.ExampleMOV BYTE PTR[DI],00 ;clearthecontentofthememory ;locationaddressedbyDI.MOV WORD PTR[1000],00 ;clearthecontentofthememory ;location[1000],[1001]indata ;segmentINC BYTE PTR[DI] ;incrementthecontentofthe ;memorylocationindatasegment ;addressedbyDIJMP DWORDPTR[2000] ;jumptoinstructionwhose ;addressisstoredinthememory ;location ;[2000],[2001],[2002],[2003]in ;datasegment SegmentDefinitionDirectives

(段定义伪指令)SEGMENT/ENDSFormat:segmentname SEGMENT …… segmentname ENDSNote:TheSEGMENT/ENDSdirectivesdefineandnameasegment.ASSUMEFormat:ASSUMESR:segmentname[,SR:segmentname]TheASSUMEdirectivestatementiswritteninfrontoftheprogramtoshowwhichsegmentiscodeone,andsoon.ThecontentofCSisevaluatedbythesystem.AndthecontentsofothersegmentregistersareevaluatedbytheMOVinstructionsinprogram.ProcedureDefinitionDirectives

(过程定义伪指令)FormatprocedurenamePROC[NEAR/FAR] …… …… RET procedurename ENDPTheNEARandFARdirectiveshowthetypeofprocedure.AssemblySourceEndDirectives

(源程序结束伪指令)FormatEND [label]NoteTheENDdirectiveshowtheassemblertheendofthesourceprogram.Thelabel,bydefault,isusuallytheonebeforethefirstinstructioninprogram.操作数ASM-86汇编程序允许汇编语言中操作数以常数、标号、变量和表达式等多种形式出现。（一）常数常数可以采用十进制数、二进制数、十六进制数、八进制数、科学表示法（8.75E-4）、ASCII码（‘A’、‘8’)。（二）寄存器如AX、AL、SI等。（三）标号标号代表一条指令的符号地址，必须用英文字母开头，中间可以是英文字母和数字。它可用作转移指令或过程调用指令中的符号地址。（四）变量变量代表内存中一段连续的存储区的地址（最低字节的地址）。它也必须用英文字母开头，中间可以是英文字母和数字。它可以在指令中表示存储器操作数。（五）表达式表达式是为了编程方便，允许编程者将一个运算式直接作为一个操作数使用，真正的操作数是这个表达式的运算结果。表达式可以由操作数和运算符组成，运算符有以下几种：（1）算术运算符算术运算符有+、-、*、/和MOD（取模，即取整数相除后的余数）等。例：MOVAX,100MOD17执行后，AX的内容是15。（2）逻辑运算符逻辑运算符有AND（与）、OR（或）、XOR（异或）、和NOT（非）。（3）关系运算关系运算符有EQ（＝）、NE（≠）、LT（＜）、GT（＞）、LE（≤）、GE（≥）等。关系运算的结果只有两个值：关系成立，结果为0FFFFH，关系不成立，结果为0。（4）特殊算符①取偏移地址算符OFFSETOFFSET算符可以求出一个标号或变量的偏移量地址。如MOVSI，OFFSETDATA1，表示将DATA1的偏移量地址送SI。②取段地址算符SEGSEG算符可以求出一个标号或变量的段地址。如MOVAX，SEGARRAY。③取类型算符TYPETYPE算符可以求出变量的类型，结果是该变量的字节数；还可以求出标号的类型，NEAR类型，结果为-1，FAR类型结果为-2。④取变量个数算符LENGTH如用DW伪指令定义变量ARRAY为10个字，ARRAYDW10DUP（？）则执行MOVCX，LENGTHARRAY后，CX的内容为10。⑤取变量字节数算符SIZEARRAYDW10DUP（？）则执行MOVCX，SIZEARRAY后，CX的内容为20。⑥合成算符PTR和THISPTR用于指定存储器操作数的临时类型。如：ARRAYDB12，34，56，78，MOVAX，WORDPTRARRAY将变量ARRAY临时指定为字变量送AX（即将3412送AX）。THISH和PTR一样也是用于规定变量的类型，如果希望某一个数据区既作为字变量使用，又可以作为字节变量来使用，可以用THIS算符把它定义为字节型，再用伪指令DW将它定义为字型变量。如：ABCEQUTHISBYTEXYZDW10DUP（？）ABC和XYZ具有相同的段地址和偏移量地址，但变量ABC为字节型；变量XYZ为字型。上面2个语句实际上相当于：XYZDW10DUP（？）ABC EQUBYTEPTRXYZ⑦短标号算符SHORTSHORT算符可以将一个标号规定为短标号类型。即标号所在的语句到引用标号的语句之间的字节数，不超过8位补码所能表示的范围（-128～127）。⑧字节分离算符HIGH和LOWHIGH和LOW分别取一个数值或表达式的高字节或低字节。如：STUFFEQU1234HMOVAH，HIGHSTUFF；AH←12HMOVAL，LOWSTUFF；AL←34H注释注释是为了程序阅读方便，而加的解释和说明。在指令之后，用；号隔开。7-1MODULARPROGRAMMING(模块化的程序设计)(P.218)TheAssemblerandLinker

(汇编程序和连接程序)(P.215)Theassemblerprogramconvertsasymbolicsourcemodule(file)intoahexadecimalobjectfile.ThelinkerprogramisprovidedwithMSDOSorMASMsothatprogrammingmodulescanbelinkedtogetherintoacompleteprogram.PUBLICandEXTRN(p.219)ThePUBLICdirectiveisplacedintheopcodefieldofanassemblylanguagestatementtodefinealabelofcode,data,orentiresegmentaspublic,sothatthelabelcanbeusedbyotherprogrammodules.Example7-3 .MODEL SMALL .DATA PUBLIC DATA1 ;declareDATA1 and DATA2 ;public PUBLIC DATA2 DATA1 DB 100DUP(?) DATA2 DB 100DUP(?) .CODE .STARTUP PUBLIC READ ;declareREADpublic READ PROC FAR MOV AH,6 ;readkeyboard MOV DL,0FFH INT 21H JE READ ;ifnokeytyped RET READ ENDP ENDTheEXTRNstatementappearsinbothdataandcodesegmentstodefinelabelsasexternaltothesegment.Ifdataaredefinedasexternal,theirsizesmustbedefinedasBYTE,WORDandDWORD.Ifajumporcalladdressisexternal,itmustbedefinedasNEARorFAR.EXAMPLE7-4.MODEL SMALL.DATA EXTRN DATA1:BYTE EXTRN DATA2:BYTE EXTRN DATA3:WORD EXTRN DATA4:DWORD.CODE EXTRN READ:FAR.STARTUP MOV DX,OFFSETDATA1 MOV CX,10STARTUP: CALL READ STOSB LOOP START.EXITENDLibraries(库)(P.220)Libraryfilesallowcommonprocedurestobecollectedintooneplacesotheycanbesuedbymanydifferentapplication.Thelibraryfileisinvokedwhenaprogramislinkedwiththelinkerprogram.

CreatingaLibraryFileAlibraryfileiscreatedwiththeLIBcommand,typedattheDOSprompt.Alibraryfileisacollectionofassembled.OBJfilesthateachperformoneprocedureortask.PleasenoticethatthenameoftheproceduremustbedeclaredPUBLICinalibraryfile.Oncethelibraryfileislinkedtoyourprogramfile,onlythelibraryproceduresactuallyusedbyyourprogramareplacedintheexecutionfile.Don’tforgettouselabelEXTRNwhenspecifyinglibrarycallsfromyourprogrammodule.EXAMPLE7-5,7-6,7-7(P.221)Macros(宏)(P.222)Amacroisagroupofinstructionsthatperformonetask,justasaprocedureperformsonetask.Thenameofthemacroandanyparametersassociatedwithitaretyped,andtheassemblertheninsertsthemacrointotheprogram.MacrosequencesexecutefasterthatprocedurebecauseaprocedureisaccessedviaaCALLinstruction,whiletheinstructionsofthemacroareplacedinyourprogrambytheassembleratthepointofusage.TheMACROandENDMdirectivedelineateamacrosequence.EXAMPLE7-8MOVE MACRO A,B ;;movesthe word- ;;sizedcontentsof ;;memorylocationB ;;intoword-sized ;;memorylocationA. PUSH AX MOV AX,B MOV A,AX POP AX ENDM

MOVE VAR1,VAR2 ;usetheMOVEmacro

PUSH AX MOV AX,VAR2 MOV VAR1,AX POP AX

PUSH AX MOV AX,VAR4 MOV VAR3,AX POP AX

MOVE VAR3,VAR4 ;usetheMOVEmacroTheModularProgrammingApproach

(模块化的程序设计方法)(P.231)Themodularprogrammingapproachofteninvolvesateamofpeoplewithdifferentprogrammingtasks.Often,theteammanagerdevelopsthesystemflowchartofshell,andthendividesitintomodulesforteammembers.Ateammembermightbeassignedthetaskofdevelopingamacrodefinitionfile.Anotherteammembermightbeassignedthetaskofdevelopingtheprocedures.Finally,severalprogramfilesormodulesmightbeformedintothefinalsystem.ProgrammingProcedure

(程序设计过程)Analyzetheprogrammingdutyanduseaproperalgorithm.Drawtheflowchart.Start/EndIn/OutProcessDirectionLineNYJudgementPageLinkSymbolFIGUREGeneralSymbolinaflowchartEdittheprogram.Assemble,linkanddebugtheprogram.EditasourcefileAssemblethesourcefile(ASM/MASM)Issyntaxwrong？NYLinkthesourcefile(LINK)NYYFIGUREProgrammingProcedureIssyntaxwrong？Debugtheobjectfile(DEBUG)Islogicwrong？NExecuteexecutablefileEndBasicArchitecture

(基本结构)Therearethreebasicarchitectureforanassemblysourceprogram.SequentialarchitectureBrancharchitectureLooparchitectureProcedureSequentialarchitecture

(顺序结构)Theprogramisexecutedintheorderthattheinstructionsarewritten.ExampleNword-sizeddataarestoredindatasegment.TheyareaccessedwithSI.ProgramtosumthesedatawithAXandstoretheresultinSUM.AllocatememoryforNWord-sizeddataandSUMInitializethesegmentregistersSI←dataoffsetaddressAX←AX+[SI]SavetheresultinSUMEndFigureTheflowchartofsummingNword-sizeddataStartAX←0SI←SI+1SI←SI+1AX←[SI]+AX⋮⋮DATA SEGMENTNUM DW 100 DUP(?) ;AssumeN=100SUM DW ? DATA ENDSCODE SEGMENT ASSUME DS:DATA,CS:CODEGO: MOV AX,DATA MOV DS,AX ;initializethedatasegmentregister XOR AX,AX ;[AX]←0 MOV SI,OFFSETNUM ;moveaoffsetaddressintoSI ADD AX,[SI] ;sumisinAX INC SI INC SI ADD AX,[SI] ;repeataddition INC SI INC SI ADD AX,[SI]

⋮ MOV SUM,AX ;storetheresultinSUM NOP NOPCODE ENDS END GOBrancharchitecture

(分支结构)Torealizethebrancharchitecture,itisusuallytojumptodifferentinstructionsunderdifferentconditionsuchasflagbits(C,Z,S,O,P),CX.TheinstructionsthatinfluencetheflagbitsareCMP,CMPSB,CMPSW,algorithmandlogicinstructions,shiftandrotateinstructions.TheinstructionsthatgeneratejumpoperationareJUMPandconditionalJUMPinstructions.Example:Programtoreadtwodatafromthekeyboard.Comparethemanddisplaythebiggeroneonthevideodisplay.A>B？NYA←BEndStartReadA,BfromthekeyboarddisplaythebiggeroneonthevideodisplaySTACK SEGMENT DW 100DUP(?)STACK ENDSCODE SEGMENT ASSUME SS:STACK,CS:CODEGO: MOV AH,1 INT 21H ;Callthe1DOSfunctiontoread ;onedatafromthekeyboard MOV BL,AL MOV AH,1 INT 21H ;Readanotherdata CMP AL,BL ;Comparethesetwodata JG LA ;ifAL>BLthenjumptoLA MOV AL,BLLA: MOV DL,AL MOV AH,2 INT 21H ;Call2DOSfunctiontodisplaythethebigger ;dataonthevideodisplay MOV AH,4CH INT 21H ;Call4CHDOSfunctiontoreturnDOSCODE ENDS END GOExample:Thedatainputfrom3portiscomparedwithareferenceparameter.Theabsolutevalueoftheirdifferenceisoutputto4port.A>B？NYA-BEndStartInputadataBfrom3portOutputthedifferenceto4portDefineareferenceparameterAB-ADATA SEGMENTA DB 6 ;DefineareferenceDATA ENDSCODE SEGMENT ASSUME DS:DATA,CS:CODEGO: MOV AX,DATA MOV DS,AX MOV BL,A IN AL,3 ;Inputadatafrom3port CMP AL,BL ;Comparewithreference JG LB ;iflargerthan,thenjumptoLB SUB BL,AL MOV AL,BL ;Difference→AL JMP LB1LB: SUB AL,BLLB1: OUT 4,AL ;Outputthedifferenceto4port NOP NOP NOPCODE ENDS END GOExample:Countseparatelythenumbersofexcellent,good,medium,passingandfailstudentinaclass.Inputendsymbol＝‘9’？NYEndStartInitializedataA＝A+1Inagradefromthekeyboard＝‘5’？Y＝‘4’？NB＝B+1Y＝‘3’？NC＝C+1Y＝‘2’？NB＝B+1YNE＝E+1DATA SEGMENTA DB 0B DB 0C DB 0D DB 0E DB 0DATA ENDSCODE SEGMENT ASSUME DS:DATA,CS:CODEGO: MOV AX,DATA MOV DS,AXBEGIN: MOV AH,1 INT 21H ;Inputagradefromkeyboard CMP AL,‘9’ ;Isendsymbol‘9’？ JE G1 ;Yes,jumptoG1A1: CMP AL,‘5’ JNE B1 INC A ;A←A+1 JMP BEGINB1: CMP AL,‘4’ JNE C1 INC B ;B←B+1 JMP BEGINC1: CMP AL,‘3’ JNE D1 INC C ;C←C+1 JMP BEGIND1: CMP AL,‘2’ JNE E1 INC D ;D←D+1 JMP BEGINE1: INC E ;E←E+1 JMP BEGING1: NOP NOP NOPCODE ENDS END GOLooparchitecture

(循环结构)Inlooparchitecture,thereisaloopinstructionsuchasLOOP、LOOPZ/LOOPEorLOOPNZ/LOOPNEthatmaketheCPUrepeatsomeinstructions.FIGUREAsinglelooparchitecture

Conditionistrue？NYLoopprocessingEndStartInitializationSavetheresultParametermodificationLoopcontrolLoopendLoopinitializationLoopprocessingExampleTheASCIIcode‘0’~’9’aredisplayedonthevideodisplay.CODE SEGMENT ASSUME CS:CODEBEGIN: MOV CX,0AH ;initializeloopcounter MOV DL,30H MOV AH,2DISPLAY: INT 21H ;callthedisplaymoduleof ;theDOS INC DL ;modifytheASCIIcode LOOP DISPLAY MOV AH,4CH INT 21H ;returntheDOSCODE ENDS END BEGINExample:AF3Hisconvertedintoadecimalandisdisplayedonthevideodisplay.

DoubleloopArchitectureAL-[BX]<0？NYDL←DL+1EndStatBX←KIOK,AL←0F3H,CX←3DL←30HAL←AL+[BX],displaytheASCIIcodeinDLBX←BX+1CX=0？YNReturntoDOSInnerloopInitializationLoopcontrolLoopprocessing

OuterloopInitializationLoopprocessingLoopcontrolDATA SEGMENTKIOK DB 100,10,1 ;theweightofdecimalDATA ENDSSTACK SEGMENT DB 100DUP(?)TOP LABEL WORDSTACK ENDSCODE SEGMENT ASSUME CS:CODE,DS:DATA,SS:STACKBEGIN: MOV AX,DATA MOV DS,AX MOV AX,SSEG MOV SS,AX MOV SP,TOP ;thestacktopisaccessedwithSP MOV AL,0F3H ;convert11110011Bintoa ;decimal LEA BX,KIOK MOV CX,3 ;outloopcountCVDEC: MOV DL,30H ;’0’CVDEC1: SUB AL,[BX] JB CVDEC2 ;ifAL-[BX]<0,jumptoCVDEC2

INC DL ;ifAL-[BX]>0,incrementDL LOOP CVDEC1CVDEC2: ADD AL,[BX]

PUSH AX ;savethecontentofAX MOV AH,2 INT 21H ;calltheDOStodisplayanASCII POP AX INC BX ;findthenextdecimalbit LOOP CVDEC MOV AH,4CH INT 21H ;returntotheDOSCODE ENDS END BEGINProcedureMainprocedureCALLCALLProcedureRETAprocedurecallMainprocedureCALLCALLProcedureRETNestedcallsProcedureRETCALLExample:Sumseveralword-sizeddataDATA SEGMENTSUM DW ?FIRST DW 6,88,13,46DATA ENDSSSEG SEGMENT DW 6DUP(?)TOP LABEL WORDSSEG ENDS ;aprocedurethatsumseveralword-sizeddataisasfollowsCODE SEGMENT ASSUME CS:CODE,DS:DATA,SS:SSEGSU PROC FAR ;delineateaprocedure PUSH SI MOV SI,0 MOV AX,0NEXT: ADD AX,[BX][SI] INC SI INC SI LOOP NEXT POP SI RET ;returnstatementSU ENDP ;endaprocedureCODE ENDS ;themainprocedureisasfollowsCLR SEGMENT ASSUME CS:CLR,DS:DATA,SS:SSEGSTART: MOV AX,DATA MOV DS,AX MOV AX,SSEG MOV SS,AX MOV SP,TOP ;thestacktopis ;accessedwithSP MOV CX,4 MOV BX,OFFSETFIRST CALL SU ;calltheprocedure MOV SUM,AX MOV AH,4CH INT 21H ;returntotheDOSCLR ENDS END START7-5EXAMPLEPROGRAMS

(程序举例)Example:Programtofindthemaximumofseveralword-sizeddataandsaveitinthememory.DATA SEGMENTBUFFER DW 11,23,0A12H,1001H,70H,12DCH DW 0F127H,6,8000H,255COUNT EQU 10MAX DW ?DATA ENDSCODE SEGMENTSTART PROC FAR ASSUME CS:CODE,DS:DATABEGIN: MOV AX,DATA MOV DS,AX

MOV CX,COUNT ;thedatanumber LEA BX,BUFFER MOV AX,[BX] ;copythefirstdataintoAX INC BX DEC CX ;theloopcountAGAIN: CMP AX,[BX] JGE NEXT ;ifAX>[BX],jumptothe ;labelnext MOV AX,[BX] ;elseexchangeAXand[BX]NEXT: INC BX LOOP AGAIN RETSTART ENDPCODE ENDS END STARTQuestion:Isthereanyothermethodtosolvethis problem?Example:Programtodisplayadoubleword-sizedhexadecimaldataonthevideodisplay.ThefirstalgorithmPositiontherightmostdigit.Compareitwith9.Ifitisbelow9,itisaddedwith30Hor‘0’Ifitisabove9,itisaddedwi