어셈블리 프로그램에 대해^^

컴파일 하니까 이런 글만 뜨네여 ^^;;
operation size not specified

=========================================================================
BITS 32

segment .text
global _start

_start

;; write(1, prompt, sizeof(prompt));

mov eax, 4 ; 4 == write system call
number
mov ebx, 1 ; 1 == stdout
mov ecx, prompt ; "What is your name? "
mov edx, prompt_len ; length("What is your
name? ");
int 0x80 ; linux system call
interrupt

;; nread = read(0, filename, sizeof(filename));

mov eax, 3 ; 3 == read
mov ebx, 0 ; 0 == stdin
mov ecx, filename
mov edx, filename_len ; buffer size
int 0x80
mov [nread], eax ; eax == the number of bytes
read

;; filename[nread-1] = '\0' <- 이부분
mov eax, nread
dec eax
mov [filename+eax],0

;; fd = open(finename, O_RDONLY);
mov eax, 5
mov ebx, filename
mov ecx, 0q
int 0x80
mov [fd], eax

;; if (fd == -1 ) {
;; write(2, open_error, sizeof(open_error));
;; exit(-1);
;; }
mov eax, [fd]
cmp eax, -1
jne if_end
mov eax, 4
mov ebx, 2
mov ecx, open_error
mov edx, open_error_len
int 0x80
if_end

;; nread = read(fd, buffer, sizeof(buffer));
mov eax, 3
mov ebx, [fd]
mov ecx, buffer
mov edx, buffer_len
int 0x80
mov [nread], eax

;; while (nread > 0) {
;; write(1, buffer, nread);
;; nread = read(fd, buffer, sizeof(buffer));
;; }

while_block
mov eax, [nread]
cmp eax, 0
jng while_end

mov eax, 4
mov ebx, 1
mov ecx, buffer
mov edx, [nread]
int 0x80

mov eax, 3
mov ebx, [fd]
mov ecx, buffer
mov edx, buffer_len
int 0x80
mov [nread], eax
jmp while_block
while_end

;; close(fd);
mov eax, 6
mov ebx, [fd]
int 0x80

;; exit(0);
mov eax, 1 ; 1 == exit system call
number
mov ebx, 0 ; return value
int 0x80

segment .data
prompt db 'filename = '
prompt_len equ $ - prompt
open_error db 'cannot open file!'
open_error_len equ $ - open_error

segment .bss
filename resb 1024
filename_len equ $ - filename
buffer resb 1024
buffer_len equ $ - buffer
fd resb 1
nread resb 1
=========================================================================

죄송합니다. 제가 인라인 어셈블러로 테스트 해보는 바람에...
mov eax, nread
dec eax
mov byte ptr filename[eax], 0

mov 에서 operation size 가 어셈블러 입장에서는 명확하지 않아서
발생한 오류 같습니다.
그래도 안되면 잘 모르겠습니다... ㅡㅡ;
GNU 어셈블러라면 movb 인스트럭션을 쓰면 되고요...

지금 사용하고 있는 어셈블러가 nasm 이거든여....
있는 책는 원서라 공부 하기 정말 힘드내여 ^^;;;