int 16h 读入缓冲区ASCII码
检测点17.1 int 16h会设置if=1

assume cs:code
code segment
start:
    mov ah,0
    int 16h

    mov ah,1
    cmp al,'r'
    je red
    cmp al,'g'
    je green
    cmp al,'b'
    je blue
    jmp sret
red:
    shl ah,1
green:
    shl ah,1
blue:
    mov bx,0b800h
    mov es,bx
    mov si,1
    mov cx,2000
s:  
    mov byte ptr es:[si],ah
    add si,2
    loop s


sret:
    mov ax,4c00h
    int 21h

code ends
end start