;将四位十六进制数的ASCII码转换为两字节四位十六进制数。
data segment
s1 db 'A5F3'
s2 dw ?
data ends
code segment
assume cs:code,ds:data
start:mov ax,data
      mov ds,ax
      mov ch,4
      mov si,offset s1
      xor bx,bx
      mov ah,0
j1:   mov al,[si]
      cmp al,39h
      jbe j2
      sub al,7
j2:   sub al,30h
      or ax,bx
      mov cl,4
      ror ax,cl
      mov bx,ax
      inc si
      dec ch
      jnz j1
      mov s2,ax
      mov ah,4ch
      int 21h
code  ends
      end start