The following $8086$ assembly program is supposed to concatenate two strings but it doesn't work properly. Why is that?

$\mathrm{.}586$

$.$MODEL FLAT

$.$STACK $4096$

INCLUDE io$.$h

$.$DATA

Inputstr$1$ BYTE $100$ DUP $(?)$

Inputstr$2$ BYTE $100$ DUP $(?)$

Outputstr BYTE $200$ DUP $(?)$

prompt$1$ BYTE "Enter the first string: $",0$

prompt$2$ BYTE "Enter the second string: $",0$

displayLbl BYTE "Concatenated string: $",0$

$.$CODE

$\_$MainProc PROC

input prompt$1,$ Inputstr$1,100$

input prompt$2,$ Inputstr$2,100$

; Copy the first string to Outputstr

mov esi, OFFSET Inputstr$1$

mov edi, OFFSET Outputstr

mov ecx, $100$

cld

rep movsb

; Find the end of the first string

mov ebx, edi ; Save the current position in ebx

lea esi, OFFSET Inputstr$2$

add edi, $100$ ; Move edi to the end of the copied string

mov ecx, $100$

repne scasb ; Find the null terminator

; Copy the second string to Outputstr

mov esi, OFFSET Inputstr$2$

mov edi, ebx ; Restore the saved position

sub edi, $1$ ; Move edi back one byte to overwrite the null terminator

mov ecx, $100$

cld

rep movsb

output displayLbl, Outputstr

mov eax, $0$

ret

$\_$MainProc ENDP

END