assume cs:codesg    ; 代码段   程序长度 cx=16(字节)

    codesg segment

start:  mov ax,2000h    ; -->  ax=2000h
    　　mov ss,ax       ; -->  ss=2000h
          mov sp,0        
          add sp,10       ; -->  sp=Ah
          pop ax          ; -->  ss:sp(2000:A) sp=Ah  [C]-->ax=0h
          pop bx          ; -->  [E]-->bx=0h  sp=sp+2=Eh  
          push ax         ; -->  ax-->[C]=0h  sp=sp-2=Ch
          push bx         ; -->  bx-->[A]=0h  sp=sp-2=Ah
          pop ax          ; -->  ax=0h        sp=sp+2=Ch
          pop bx          ; -->  bx=0h        sp=sp+2=Eh
    
          mov ax,4c00h  
          int 21h         ; -->program terminated normally

      codesg ends
end start