Write a program to copy block of data from source to destination in 8086?

Data1 segment

str1 db 'john cox'

str_length equ ($-str1); db 100 dup(?)

str2 db str_length dup(?)

data1 ends

code1 segment

assume cs:code1, ds:data1, es:data1

start: mov ax, data1

mov ds, ax

mov es, ax

lea si, str1

lea di, str2

mov cx, str_length

cld

rep movsb

mov ah, 4ch

int 21h

code1 ends

end start