assume cs:code,ds:data

data segment
        db 'welcome to masm!'
        db 2h,24h,71h,0h    
data ends

code segment
        start: mov ax,data   
                mov ds,ax     
                sub si,si             
                mov ax,0B800h     
                mov es,ax       
                mov di,10h    
                        
            s0: mov cx,[di]             
                mov ax,cx            
                jcxz ok          
                            
                mov cx,16       
                sub bx,bx       
                sub bp,bp      
            s1: mov dl,[bx]       
                mov es:[bp+720h+si],dl 
                mov es:[bp+721h+si],al  
                inc bl                  
                add bp,2
                loop s1              
                                        
                inc di              
                add si,160          
                loop s0            
                        
            ok: mov ax,4c00h
                int 21h
                                        
code ends
end start