;输入四个字符,回车换行后显示与它等值的二进制数.
data segment
h1 db 16 dup(?)
data ends
code segment
stack segment stack
db 100 dup(?)
stack ends
assume cs:code,ds:data,ss:stack
start: mov ax,data
       mov ds,ax
       lea si,h1
       mov cx,4
l1:    mov ah,1
       int 21h
       cmp al,30h
       jb exit      ;小于输入的字符0退出 
       cmp al,39h
       jbe j1       ;小于等于输入的字符9跳转 
       cmp al,41h  
       jb exit      ;小于输入的字符A退出 
       cmp al,66h
       ja exit      ;大于输入的字符f退出 
       cmp al,61h
       jae x1        ;大于等于输入字符a跳转 
       cmp al,46h
       ja exit      ;大于输入的字符F退出
       sub al,37h   ;41h-0ah=37h
       jmp j2
x1:    sub al,57h   ;61h-0ah=57h
       jmp j2
j1:    sub al,30h
j2:    mov di,4
j3:    cbw          ;将al转换为ax
       mov bl,2
       div bl
       mov [si],ah  ;将(余数)二进制数放入h1开始单元
       inc si
       dec di
       cmp di,0
       jnz j3
       loop l1
;*******************************
       mov dl,'H'
       mov ah,2
       int 21h    
       mov dl,'='
       mov ah,2
       int 21h    
;*******************************
       lea si,h1
       mov cx,4
l3:    mov di,4
       mov bx,3
l4:    mov dl,[si+bx]
       add dl,30h
       mov ah,2
       int 21h
       dec bx
       dec di
       cmp di,0
       jnz l4
       add si,4      
       loop l3
;___________________
       mov dl,'B'
       mov ah,2
       int 21h    
exit:  mov ah,4ch
       int 21h
code   ends
       end start