DOS 16位ASM如何将数据保存在内存中？

Question

I am new to ASM. I have question regarding how data saved in memory.

Here is my ASM 16 bit code

;db.com
.model small
.code
org 100h
start:
jmp proses
A db '123'
B dw 0abcdh
proses:

int 20h
end start

Then I try to debug with -d command

The above picture shown that A variable in correct order in hexa value, but B variable in CD then AB .

My question is why data in A variable saved differently with B variable can you please explain me?

Answer 1

x86 is using little endian, so word will be stored as low-byte, high-byte and dword as low-word, high-word

0x1020 will be 0x20 0x10 in memory
and 0xabcd1234 will be 0x34 0x12 0xcd 0xab

by defining db <string> you order the assembler to use the string as a sequence of bytes, and each byte is stored in the same order, one by one

so eg
db '012345",13,0 will be 0x30 0x31 0x32 0x33 0x34 0x35 0x0D 0x00