??6.5?????Z=((X Y)*8-X)/2 - PowerPoint PPT Presentation

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**??6.5?????Z=((X Y)*8-X)/2**

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Title: Author: WANG Last modified by: Billgates Created Date: 4/30/2003 2:16:35 PM Document presentation format: – PowerPoint PPT presentation

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Title: ??6.5?????Z=((X Y)*8-X)/2

1
?6?
2
?6?6.2 ??????

6.2.1 ??????
???????????????,???????????????,???????
?????????????
?????????????????

??6.5?????Z((XY)8-X)/2 ??6.6
?????????????,????16 ??????ASCII???
3
?6??6.6(2) ???

???
ASCII db 30h,31h,32h,33h,34h,35h,36h,37h,38h,39h
??0 9?ASCII?
db 41h,42h,43h,44h,45h,46h
??A F?ASCII?
hex db 04h,0bh
??????

4
?6??6.6(2) ???

???
mov bx,offset ASCII
BX??ASCII??
mov al,hex
AL????16???
????ASCII??????
and al,0fh
???4?????,?4??0
xlat
??AL?DSBXAL

XLAT
5
?6??6.6(2) ???(?)

mov dl,al ????DL?AL
mov ah,2 02?DOS????
int 21h ????ASCII???
mov al,hex1 ??????????
and al,0fh
xlat
mov dl,al
mov ah,2
int 21h

XLAT
6
?6?6.2.2 ??????

??????????????????
??????????,?CMP?TEST???????????
????Jcc?JMP????????
?????
?????
?????
?????

7
?6??????

??????,???????????
????????????????????

??????
8
?6???AX?????????

cmp ax,0
jge nonneg ????(AX0),??
neg ax ?????,??
nonneg mov result,ax ????

?????? cmp ax,0 jl yesneg ????(AXlt0),?? jmp
nonneg yesneg neg ax ?????,?? nonneg mov
result,ax ????
9
?6??????

?????????2??????,???????1??????
???1???????????JMP?????2?????

????BX????
10
?6???BX????

shl bx,1 BX?????CF??
jc one CF1,?????1,??
mov dl,30h
CF0,?????0DL?30H0
jmp two ???????????
one mov dl,31h DL? 31H1
two mov ah,2
int 21h ??

???JNC??JC
11
?6???BX????(?)

shl bx,1 BX?????CF??
jnc one CF0,?????0,??
mov dl,31h
CF1,?????1DL?31H1
jmp two ???????????
one mov dl,30h DL? 30H0
two mov ah,2
int 21h ??

????????
12
?6???BX????(??)

mov dl,0 DL?30H0
shl bx,1 BX?????CF??
jnc two CF0,?????0,??
mov dl,1
CF1,?????1DL?31H1
two mov ah,2
int 21h ??

??????,???????????

13
?6???BX????(???)

mov dl,0
shl bx,1 BX?????CF??
adc dl,30h
CF0,DL?030h030H0
CF1,DL?030h131H1
two mov ah,2
int 21h ??

14
?6??????
????????????????????,????????????????
or ah,ah cmp ah,0 jz function0 dec ah cmp
ah,1 jz function1 dec ah cmp ah,2 jz function2
15
?6?6.2.3 ??????

?????????????????,????????
??????????3???
??????????????????,???????????????
???????????????,????????????????
????????????????,????????

??????
16
?6?????

??????????????????
???????????????,??????????,????????
?????????,WHILE_DO
?????????,DO_UNTIL
??????????????,?????????,????
??????
??????

??
17
?6????????????
18
?6? ??????

??????????????????
????????LOOP?JCXZ??
?????????????????CX
???
?????LOOP???CX?1???????0

19
?6???????BL??
???

mov cx,8 CX?8(????)
again shl bl,1 ???CF,???????
mov dl,0 MOV?????CF
adc dl,30h DL?030HCF
CF??0,?DL?' 0 '
CF??1,?DL?' 1 '
mov ah,2
int 21h ??
loop again
CX?1,??CX???0,???

???
?????? ??????
20
?6???????

??????????????????????
???????????????????
??????????????????????,????????????????????????,??
????????

21
?6????0??????

???
string db 'Let us have a try !',0
???
mov bx,offset string
again mov dl,bx
cmp dl,0
jz done ?0??
mov ah,2 ??0,??
int 21h
inc bx ???????
jmp again
done

?????? ??????
22
?6?6.2.4 ?????

??????????????????,????????????????,??????
??????????????,????????,????????
???(????)????CALL???????(?????)
???????RET???????

23
?6?1 ???????

?????,????????????PROC?ENDP??,????
??? PROC NEARFAR
???
??? ENDP
???????????????????????,???????
NEAR??(?????)??????????????????
FAR??(?????)???????????????????

24
?6?1 ???????
???? XSEG SEGMENT SUBT1
PROC FAR
RET SUBT1 ENDP
CALL SUBT1 XSEG ENDS YSEG SEGMENT
CALL SUBT1
YSEG ENDS
?????????? CSEG SEGMENT MAIN PROC FAR
CALL SUBT
RET MAIN
ENDP SUBT PROC NEAR
RET SUBT ENDP CSEG ENDS
25
?6??????????