x86 CMP instruction not working for a single word comparison

Question

I am having troubles with the CMP instruction when comparing single words (2 bytes).
The following is my main.asm:

[org 0x7c00]

mov bx, HELLO_MSG
call print_string

mov bx, GOODBYE_MSG
call print_string

jmp $

%include "print_string.asm"

; Data
HELLO_MSG:
    db 'Hello, World!', 0
GOODBYE_MSG:
    db 'Goodbye!', 0

This is the print_string.asm file:

print_string:
    pusha
    mov ah, 0x0e
    loop:
        call print_char
        cmp word [bx], 0
        jne loop
    popa
    ret

print_char:
    mov al, [bx]
    int 0x10
    add bx, 1
    ret

This code prints out the following:

Hello World! Goodbye!Goodbye!

I know that when I add

db 0

in between the HELLO_MSG and the GOODBYE_MSG, the code will work as intended. Can anyone explain why CMP will only work when there are 4 bytes of 0 between the strings?

If anyone is interested in looking at the compiled output, here it is:

bb  23  7c  e8  08  00  bb  31  7c  e8  02  00  eb  fe  60  b4
0e  e8  07  00  83  3f  00  75  f8  61  c3  8a  07  cd  10  83           
c3  01  c3  48  65  6c  6c  6f  2c  20  57  6f  72  6c  64  21
00  47  6f  6f  64  62  79  65  21  00  00  00  00  00  00  00           
00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
*           
00  00  00  00  00  00  00  00  00  00  00  00  00  00  55  aa

The 55 aa at the end is added by me because I am using this code as a boot loader.

Answer 1

CMP 指令不适用于单字比较的原因是一个字必须包含 2 个字节。由于编译的输出显示两条消息之间只有 1 个字节，因此您需要将 CMP 指令的大小从字更改为字节：

cmp byte [bx], 0

我错误地假设编译后的输出格式按 2 排列字节。但是，在 Michael Petch 的以下评论的帮助下：

第 4 行以 00 47 6f 开头，每个值（用空格分隔）都是一个字节，而不是 2 个字节。00是单个字节的0，而不是两个字节的0

我能够认识到自己的错误。