assembly x86(nasm)串比较

预留字符串口令,输入口令串与预留密码串比较。若匹配则显示“MATCH！CONGRATULATION”,否则显示“NOMATCH!”,并让用户重新输入，程序能对口令进行测试，但测试次数最多3次，若3次输入密码皆错，给出相应的提示信息，程序退出。

两种做法：

data    segment

message        db    'This is a sample program of passward'

            db    0dh,0ah,'Please strike the key!',0dh,0ah,'$'

passward     db     'huangchangsheng$'

buf1         db

            db  ?

            db      dup('$')

FAULT         db     0dh,0ah,'NOMATCH!Please enter again!',0dh,0ah,'$'

RIGHT         db     0dh,0ah,'MATCH!CONGRATULATION!',0dh,0ah,'$'

ending        db    0dh,0ah,'You have typed the wrong passward for three times!',0dh,0ah,'$'

data    ends

code    segment

assume    cs:code,ds:data

start:

            mov    ax,data

            mov    ds,ax

            mov    dx,offset message

            mov    ah,

            int    21h

            mov cl,

            jmp input

rinput:

            mov    dx,offset FAULT                ;提示错误

            mov    ah,

            int    21h

input:

            lea    dx, buf1                     ;字符串输入

            mov ah, 0ah

            int 21h

            xor si,si

strcmp:                                        ;串比较

            mov al,passward[si]

            cmp al,'$'

            jz output2

            mov al,passward[si]

            cmp buf1[si+],al

            jnz output1

            inc si

            jmp strcmp

output1:

            loop rinput

            mov    dx,offset ending

            mov    ah,

            int    21h

            jmp exit

output2:

            mov    dx,offset RIGHT                ;提示正确

            mov    ah,

            int    21h

exit:

            mov    ah,4ch

            int    21h

code    ends

end    start

第二种比较难受，因为di和附加段搞了好久，然后是看大佬代码才发现自己错哪了的

https://blog.csdn.net/pengwill97/article/details/79249631传送门

data    segment

message        db    'This is a sample program of passward'

            db    0dh,0ah,'Please strike the key!',0dh,0ah,'$'

buf1         db     ,?, dup('$')

FAULT         db     0dh,0ah,'NOMATCH!Please enter again!',0dh,0ah,'$'

RIGHT         db     0dh,0ah,'MATCH!CONGRATULATION!',0dh,0ah,'$'

ending        db    0dh,0ah,'You have typed the wrong passward for three times!',0dh,0ah,'$'

data    ends

ext segment

passward db 'huangchangsheng$'

ext ends

code    segment

assume    cs:code,ds:data,es:ext

start:

            mov    ax,data

            mov    ds,ax

            mov ax,ext

               mov es,ax

            mov    dx,offset message

            mov    ah,

            int    21h

            mov cx,

            jmp input

rinput:

            mov    dx,offset FAULT                ;提示错误

            mov    ah,

            int    21h

input:

            lea    dx, buf1                     ;字符串输入

            mov ah, 0ah

            int 21h

            lea di,passward

            lea si,buf1+

            push cx

            mov cl,buf1+

            repz cmpsb                        ;当前字符相同则继续循环

            jz output2

            jnz output1

output1:

            pop cx

            loop rinput

            mov    dx,offset ending

            mov    ah,

            int    21h

            jmp exit

output2:

            mov    dx,offset RIGHT                ;提示正确

            mov    ah,

            int    21h

exit:

            mov    ah,4ch

            int    21h

code    ends

end    start

如果使用repz cmpsb，密码应该放在附加段，不然可能会出bug，原因可能是di是目的变址寄存器，可用来存放相对于 ES 段之目的变址指针。

巴特西

assembly x86(nasm)串比较

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