.386
.model flat, stdcall
.data
source  BYTE  "This is the source string",0
target  BYTE  SIZEOF source DUP('#')
.code

start:
    ;write your code here
        mov  esi,0
    mov  ecx,SIZEOF source
    L1:
    mov  al,source[ecx]
    mov  target[esi],al
    inc  esi
    loop L1

    mov  al,source[ecx]
    mov target[esi],al
    ret
    END start