汇编语言 循环判断 输入是否为数字

源码：

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
TIP:
    lea dx,string1
    mov ah,09h
    int 21h
    mov ah,01h
    int 21h
    cmp al,30h
    jnc GOON
    lea dx,string3
    mov ah,09h
    int 21h
    jmp TIP
GOON:
    cmp al,3ah
    jnc DONE
    lea dx,string2
    mov ah,09h
    int 21h
    jmp EXIT
DONE:
    lea dx,string3
    mov ah,09h
    int 21h
    jmp TIP
EXIT:
    mov ah,4ch
    int 21h
code ends
    end start

运行截图：