517.asm

本书为清华大学第二版汇编语言的课后题详解

;517.asm

        .model  small
        .data
mem     db  4 dup(?),13,10,'$'
        .code
main    proc  far
start:
        mov   ax,@data
        mov   ds,ax
        mov   ax,2A49h
        mov   ch,4
        mov   si,3
rotate: mov   cl,4
        rol   ax,cl
        mov   bl,al
        and   bl,0fh
        add   bl,30h
        cmp   bl,3ah
        jl    printit
        add   bl,07h
printit:mov   mem[si],bl
        dec   si
        dec   ch
        jnz   rotate
        lea   dx,mem
        mov   ah,9
        int   21h
        mov   ax,4c00h
        int   21h
main    endp
        end   start