Thiết kế và lập trình hệ thống - Chương 23

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StringOperations.
MOVS,LODS,STOS,INS,OUTS
Allowdatatransfersofabyte,awordoradoubleword,orifrepeated,a
blockofeachofthese.
TheDflag-bit(direction),SIandDIareimplicitlyused.
•D=0:AutoincrementDIandSI.
UseCLDinstructiontoclearthisflag.
•D=1:AutodecrementDIandSI.
UseSTDinstructiontosetit.
DI:
Accessesdataintheextrasegment.CanNOToverride.
SI:
Accessesdatainthedatasegment.Canbeoverriddenwithsegment
overrideprefix.
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UMBC
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StringOperations.
LODS:
LoadsAL,AXorEAXwithdatastoredatthedatasegment(orextra
segment)+offsetgivenbySI.
SIisincrementedordecrementedafterwards:
STOSB:
StoresAL,AXorEAXtotheextrasegment(ES)+offsetgivenbyDI.
EScannotbeoverridden.
DIisincrementedordecrementedafterwards:
LODS

✁✂
✁
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☎
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✁✝
✞
✟

✠
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✟
☛☞
☎
✟
☛
✞
✟
☛ ✌
✍✏✎
✑
✒ ✓

✁✂
✁
✄
✔
LODSB
☎
✁✕
✞
✟
✠
✡
✟
☛☞
☎
✟
☛

✞
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☛ ✌
✍✏✎
✄
LODSD
☎
✆
✁✝
✞
✟
✠
✡
✟
☛☞
☎
✟
☛
✞
✟
☛ ✌
✍✏✎
✑
doubleword.
LODS
✆✟
✠

✁✂
✁

✄
☎
✖✘✗
✙✚
✚
✒ ✛
✙
✟
✜
STOS

✁✂
✁
✄
☎
✆✟
✠
✡

☛☞
✞
✁✝
☎
✟
☛
✞
✟
☛ ✌
✍✏✎
✢

✒ ✓

✁✂
✁
✄
✔
STOSB
☎
✆✟
✠
✡

☛☞
✞
✁✕
☎

☛
✞

☛ ✌
✍✏✎
✄
STOSD
☎
✆✟
✠
✡

☛☞

✞
✆
✁✝
☎

☛
✞

☛ ✌
✍✏✎
✑
word.
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✌✎✍
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✒
✏✓
✔
✄
✄

✆
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3
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StringOperations:
LODSW
EAX
EBX

ECX
EDX
ESP
EBP
EDI
ESI
CS
DS
ES
SS
✁
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*10H
✝
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+
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✞
✞
11000
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✟
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+/-
2
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✞✠✟✡
☛
✟☞
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✝
✌✎✍
☛
✏✑
✒
✏✓
✔
✄
✄
✆
✝
✕✖
✁
✗
✘ ✙

✞✚
✛✜
✑
4
✢
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✟
✌
✖✤
✑✦✥
✤
✑
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✜
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☞
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UMBC
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StringOperations.
REPprefix:
ExecutestheinstructionCXtimes.
NOTE:REPdoesnotmakesensewiththeLODSinstruction.
CLD
✜

✖

✆

✕
✂
☛✁
✂
.STARTUP
MOV AX
✄
☎ ✆
✝
☎
☎ ✞
.EXIT
END
☎
✟
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✒☞☛
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✙✌
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✌
✍
✛
✙

✜
.CODE
☎
✁
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✚
✙✎
✎
✗
✒ ✛
✙
✍
✎
✙✏
✆
✝
☎
☎
✜
MOV ES
✄
AX
MOV DI
✄
☎
☎
✖
✓
✓

✎
✙
✡
☎
✜
MOV CX
✄
✢ ✑
✒
✝
☎
☎
✕
✍
✔
✛
✠
✍✓
☛
✡
✜
MOV AX
✄
☎ ✔
✢
☎ ✞
☎
✕
✍
✔

✛
✔
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✒ ✕
✓
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☛
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✠
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✔
✚
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☎
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✔
✚
✡
✖

✙
✎
✠
✚
✙
✙
☛
✜
✂✁
✄
☎ ✆
✝
✄
✞✠✟✡
☛
✟☞
✝
✝
✌✎✍
☛
✏✑
✒
✏✓
✔
✄
✄
✆
✝
✕✖
✁

✗
✘ ✙
✞✚
✛✜
✑
5
✢
✔✎✣
✟
✌
✖✤
✑✦✥
✤
✑
✑
✜
✧✎★
✩✪
☞
✝
✫
UMBC
U M B C
U
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S

I
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O
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C
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✮✠✯
✰✱
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✳
✴
✰✎✵
StringOperations.
MOVS:
Movesabyte,wordordoublewordfromdatasegmentandoffsetSI
toextrasegmentandoffsetDI.
Increments/decrementsbothDIandSI:
INS/OUTS(notavailableonthe8086):
Transfersabyte,wordordoublewordofdatafrom/toanI/Odevice
into/outoftheextra/datasegment+offsetDI/SI,respectively.