section .data
 minha_string db 'ABZXXZZZZZHCDEEFGHX', 0 ; String com terminador 0
 achou_msg db 'Achou 3 X!', 0xA
 achou_len equ $ - achou_msg
 contador dd 3
section .text
 global _start
_start:
 mov esi, minha_string ; ESI aponta para o início da string
procurar:
mov al, [esi] ; pega o byte apontado por ESI e coloca em AL
inc esi
cmp al, 0 ; Chegou ao final da string? (terminador 0)
 je nao_achou
 cmp al, 'X' ; Comparar caractere atual com 'X'
 je achou
 jmp procurar ; Continua procurando
achou:
 dec dword [contador]
 cmp dword [contador], 0
 je achou3
 jmp procurar
nao_achou:
 ; se não quiser fazer nada, apenas sair
 jmp sair
achou3:
 ; escreve mensagem "Achou o X!"
 mov eax, 4 ; syscall write
 mov ebx, 1 ; STDOUT
 mov ecx, achou_msg
 mov edx, achou_len
 int 0x80
 jmp sair
sair:
 mov eax, 1 ; syscall exit
 xor ebx, ebx
 int 0x80

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