[SOLVED] assembly error: "instruction operands must be the same size"

assembly error: "instruction operands must be the same size"

I'm very new at this and I'm trying to move values from one array to the other, it suppose to be:

vec1 = 1, 2, 3, 4, 5
vec2 = 5, 4, 3, 2, 1

but I get an error: "instruction operands must be the same size"

TITLE program

     .386
     .model flat
     extern _ExitProcess@4:Near
     .data

     vec1 WORD 1, 2, 3, 4, 5; original array
     vec2 WORD 5 DUP(?)
     .code                 
_main:

    mov ebx, 0
    mov ecx, lengthof vec1
    DO:
    mov eax, vec1[ebx]
    mov vec2[ecx], eax
    inc ebx
    loop DO

    push    0                       
    call    _ExitProcess@4          

    end   _main

please help.

Solution

The first thing I'd be looking at is the fact the a WORD is 16 bits wide and eax is 32 bits wide. So, when you load something into eax (without an explicit size specifier), you'll get 32 bits rather than 16.

In addition, I'm not convinced that your values of ecx will be what you expect - you should check that, keeping in mind that it needs to iterate from n-1 down to 0 inclusive. The way you have it, it's going from n to 1.