code segment
assume cs:code
org 100h
start:jmp begin
str1 db 'FEDCBA'
n equ $-str1
str2 db n dup(?)
db '$'
begin:push cs
pop ds
push cs
pop es
mov cx,n
lea si,str1
lea di,str2
add si,n
dec si
@m1:
mov al,[si]
mov [di],al
dec si
inc di
loop @m1
lea dx,str2
mov ah,9
int 21h
mov ah,4ch
int 21h
code ends
end start