Ensamblador - Como leer de un string con LEA

; counts the number of characters of a zero terminated string.

name "counter"

org 100h

jmp start

str1 db 'abcdefg hijklmnop qrstvuwxyz', 0

start: lea bx, str1 ; load address of string.
mov ax, 0 ; reset counter.

compare: cmp [bx], 0 ; is it end of string?
je done ; if zero, then it's the end.
inc ax ; count char.
inc bx ; next memory position in string.
jmp compare

; print result in binary:
done:
mov bx, ax
mov cx, 8
print: mov ah, 2 ; print function.
mov dl, '0'
test bl, 10000000b ; test first bit.
jz zero
mov dl, '1'
zero: int 21h
shl bl, 1
loop print

; print binary suffix:
mov dl, 'b'
int 21h

; wait for any key press....
mov ah, 0
int 16h

ret