Today’s review of the compilation.

datas segment use16 
str1 db "hello world!", 0dh, 0ah, "$" 
datas ends 

stacks segment use16 
          db 256 dup(0) 
stacks ends 

codes segment use16 
          assume cs:codes, ds:datas, ss:stacks 
start: mov ax , datas 
         mov ds, ax 
         lea dx, str1 
         mov ah, 09h 
         int 21h 
         mov ah, 4ch 
         int 21h 
codes ends 
         end start