匯編程序42：實驗11 編寫子程序 -开发者知识库

 1 assume cs:code,ds:data
 2 //鎖定小寫字母,從而改寫,使用cmp與條件指令配合
 3 data segment
 4     db "Beginner's All-purpose Symbolic Instruction Code.",0
 5 data ends
 6 
 7 code segment
 8     begin:
 9           mov ax,data
10           mov ds,ax
11           call letterc
12           mov ax,4c00h
13           int 21h
14   letterc:
15           mov si,0
16           mov cx,30h
17      main:
18           mov al,ds:[si]
19           cmp al,0
20           je ok
21           cmp al,61h
22           jb next
23           cmp al,7ah
24           ja next
25           and al,11011111b
26           mov ds:[si],al
27      next:      
28           inc si
29           loop main
30        ok:
31           ret
32 code ends
33 
34 end begin

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