Assembly login program always returning "true" -


i'm working on presentation , came across code great addition presentation. problem if enter "hello123" (for example), program assumes "hello123" , "hello" matched.

this code came here. wasn't able comment code because of low rep. did research , tried myself can't sort out problem. grateful if can me. 

.model small .stack 100h .data     db "hello$"     login db "please log in: $"     lg db 21          ;<=== maximum number of chars allowed (20).        db ?           ;<=== number of chars user entered (?).        db 21 dup(0)   ;<=== array of chars (finish 0dh=13).     hellomsg db 0dh, 0ah, "hello message$"  .code main proc mov ax, @data mov ds, ax  mov ah, 09h lea dx, login int 21h  mov ah, 0ah mov dx, offset lg     ;<=== tell int 21h store captured string here. int 21h  mov si, offset lg + 2 ;<=== point array of chars. mov di, offset      ;<=== point user. ck:  ;check end of user.   mov dh, [di] cmp dh, '$' je  hi                ;<=== end reached. chars match.  ;check end of input.   mov dl, [si]          ;<=== current entered char. cmp dl, 13 je  bye               ;<=== end reached. input shorter.  ;compare current entered char current user char.   cmp dl, dh jne bye               ;<=== current chars different. inc si                ;<== next entered char. inc di                ;<== next user char. jmp ck                ;<== repeat.  hi: mov ah, 09h lea dx, hellomsg int 21h  bye: mov ah, 4ch int 21h  main endp  end main

so time burned not knowing 1 line of code end all. 

cmp byte ptr lg + 1, 5

add before ck:

ck:  ;check end of user.   mov dh, [di] cmp dh, '$' je  hi                ;<=== end reached. chars match.

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