匯編中的目錄

Question

我必須讀取 2 個目錄（dir1 和 dir2）並創建 dir1/dir2 目錄。 我的問題是： cmp al,13什么作用？ 當我寫mov ah,01h,int 21h ，in 將是我讀取的字符，它只有一個字符（例如“a”），那么如何將 al 與 0 進行比較？

assume cs:code,ds:data

data segment
mesaj1 db 10,13,'First dir $',10,13
mesaj2 db 10,13,'Second dir $',10,13
dir1 db 30 dup(?)
dir2 db 30 dup(?)
pnf db 10,13,'Path not found.$',10,13
acd db 10,13,'Acces denied, or pathname already exists.$',10,13
gata db 10,13,'The directory was created.$',10,13
data ends

code segment
start:
mov ax,data
mov ds,ax

;read the first direcory
mov ah,09h
mov dx,offset mesaj1
int 21h

mov si,0
mov ah,01h
int 21h
bucla1:
mov dir1[si],al
inc si
int 21h
cmp al,13                    ;HERE
je sf1
mov dir1[si],al
jmp bucla1
sf1:
mov dir1[si],0

;read the second directory
mov ah,09h
mov dx,offset mesaj2
int 21h

mov si,0
mov ah,01h
int 21h
bucla2:
mov dir2[si],al
inc si
int 21h
cmp al,13                     ;HERE
je sf2
mov dir2[si],al
jmp bucla2
sf2:
mov dir2[si],0

mov ah,3Bh 
mov dx,offset dir1
int 21h
jc eroare

mov ah,39h 
mov dx,offset dir2
int 21h
jc er
mov ah,09h
mov dx,offset gata
int 21h

eroare:
cmp ax,3
je pathnotfound
jmp sf

pathnotfound:
mov ah,09h
mov dx,offset pnf
int 21h
jmp sf

er:
cmp ax,3
je pathnotfound
cmp ax,5
je accesdenied

accesdenied:
mov ah,09h
mov dx,offset acd
int 21h

sf:
mov ax,4C00h
int 21h
code ends
end start

Answer 1

檢索到的字符由其ascii字符代碼表示，代碼13是回車

它正在測試您第二次調用 int 21h 返回的字符是否為回車符。 如果是，則跳出循環，否則繼續循環並處理后續字符。

mov ah,01h       ; 01h = Read character
int 21h          ; Call (do read)
bucla1:
mov dir1[si],al ; Store result
inc si          ; Increase si
int 21h         ; Call again (do read)
cmp al,13       ; Is carriage return?
je sf1          ; Yes, jump out of loop
mov dir1[si],al ; Store result
jmp bucla1      ; Loop
sf1:
mov dir1[si],0  : Null terminate result

參考： https : //en.wikipedia.org/wiki/ASCII