汇编--编写z = |x-y|

    .model small
    .stack
    .data
    x db 1
    y db 5
    z db '?' 
    .code
start:
    mov ax,@data
    mov ds,ax
    xor ax,ax
    mov al,x
    cmp al,y
    jb  xly     ;(al)<y 则转移
    sub al,y
    mov z,al
    jmp ok
xly:
    mov al,y
    sub al,x
    mov z,al
ok:
    mov ax,4c00h
    int 21h 
    endp