阅读以下宏汇编语言程序，源程序名为：JXXYY6.ASM。说明该程序的功能和作用；说明其中的宏定义部分哪些在汇编后所形成的列表文件“JXXYY6.LST”中有宏展开， 哪些没有，为什么？
              ;sparaent a 16 bit digitor to 4 register al,bl,cl,dl
              prohead  macro
                     assume cs:code,ds:data,es:data
              main     proc far
              start:
                 push ds
                     xor ax,ax
                     push ax
                     mov ax,data
               mov ds,ax
               endm
              shift   macro opr1,opr2,opr3
                     mov opr1,opr2
                     mov cl,4
                     shl al,cl
               mov opr3,opr2
               and opr3,0fh
               endm
              data    segment
              dat1     dw 6789h
              data     ends
              code     segment
               .lall
               prohead
                     mov dx,dat1
                     .xall
                       shift al,dh,bl
                       .sall
                     shift ch,dl,dl
                     mov cl,ch
               ret
              main     endp
              code     ends
                 end start