DATAS SEGMENT
   db 'welcome to masm!'
DATAS ENDS

STACKS SEGMENT
    ;此处输入堆栈段代码
STACKS ENDS

CODES SEGMENT
    ASSUME CS:CODES,DS:DATAS,SS:STACKS
START:
    MOV AX,DATAS
    MOV DS,AX
    mov ax,0B800h
    mov es,ax
    mov bx,0
    mov cx,16
    mov di,0
  
 s: mov byte ptr es:[bx],[di]  ;提示这一行有错误
    mov byte ptr es:[bx+1],2h
    add bx,2
    inc di
    loop s
    MOV AH,4CH
    INT 21H
CODES ENDS
    END START
怎么错了，求指教！

知道了，不能内存对内存直接传送！

可以用别的指令替代

DATAS SEGMENT
   db 'welcome to masm!'
DATAS ENDS

CODES SEGMENT
    ASSUME CS:CODES,DS:DATAS
START:
    MOV AX,DATAS
    MOV DS,AX
    mov ax,0B800h
    mov es,ax
    mov si,0
    mov cx,16
    mov di,0
    mov ah,2h
    cld        ;方向标志,影响lodsb等指令


 s: lodsb    ;等同mov ds:[si],al ... inc si
    stosw    ;等同mov es:[di],ax ... add di,2
    loop s
    mov ah,7    ;等待键盘输入
    int 21h    ;调用dos
    MOV AH,4CH
    INT 21H
CODES ENDS
    END START