依次显示‘a-'z',按下esc后改变颜色。运行却没反应（由于是自学，犯了低级错误希望大家容忍）

assume cs:code,ds:data
data segment
dw 0,0
data ends
stack segment
db 16 dup (0)
code segment
start: cli
mov ax,data
mov ds,ax

    mov ax,0
    mov es,ax

            mov ax,stack
      mov ss,ax
      mov sp,16

    mov ax,es:[9*4]
    mov ds:[0],ax
    mov ax,es:[9*4+2]
    mov ds:[2],ax

    mov word ptr es:[9*4],offset int9
    mov word ptr es:[9*4+2],cs

sti

    mov ax,0b800h
    mov es,ax
    mov byte ptr es:[160*12+80],'a'
 s0:cmp byte ptr es:[160*12+80],'z'
    ja s1
    call delay
    add byte ptr es:[160*12+80],1
    jmp s0
 s1:mov ax,0
    mov es,ax

    mov ax,ds:[0]
    mov es:[9*4],ax
    mov ax,ds:[2]
    mov es:[9*4+2],ax

    mov ax,4c00h
    int 21h

delay: push dx
push ax

    mov ax,100h
    mov ax,0
 s3:sub ax,1
    sbb dx,0
    cmp ax,0
    jne s3
    cmp dx,0
    jne s3
    pop ax
    pop dx
    ret

int9: push ax
push es

in al,60h
    pushf

    call dword ptr ds:[0]
    cmp al,1
    jne s4

mov ax,0b800h
mov es,ax
    add byte ptr es:[160*12+80+1],1

 s4:pop es
pop ax
    iret

code ends
end start

data ends
stack segment
db 16 dup (0)
code segment
start: cli
mov ax,data
mov ds,ax
mov ax,0
mov es,ax

        mov ax,stack
  mov ss,ax
  mov sp,16

mov ax,es:[9*4]
mov ds:[0],ax