汇编循环旁支语句

data segment
    string1 db 'Please input a number:',0dh,0ah,'$'
    string2 db 0dh,0ah,'It is a number!',0dh,0ah,'$'
    string3 db 0dh,0ah,'It is not a number!',0dh,0ah,'$'
data ends
code segment
    assume cs:code,ds:data
start:
    mov ax,data      
    mov ds,ax        ;初始化ds
    lea dx,string1           ;取string1的偏移地址，放入dx
    mov ah,09h
    int 21h           ;从键盘输入字符串
    mov ah,01h
    int 21h     ;从键盘输入字符串
    cmp al,30h               ;和‘0’相比较
    jnc GOON            ;无进位转移到goon
    lea dx,string3      ;取string3的偏移地址，放入dx
    jmp EXIT      ;跳转到exit
GOON:
    cmp al,3ah       ;与‘：’相比较
    jnc DONE      ;无进位转移到done
    lea dx,string2    ;取string2的偏移地址，放入dx
    jmp EXIT
DONE:
    lea dx,string3         ;取string3的偏移地址，放入dx
    jmp EXIT
EXIT:
    mov ah,09h
    int 21h           ;从键盘输入字符串
    mov ah,4ch
    int 21h             ;从键盘输入字符串
code ends
    end start