.386
.model flat, stdcall
.data
array dword 1,2,3,4,5,6,7,8
.code
start:
    ;write your code here
    mov esi, OFFSET array
    mov ecx, LENGTHOF array -1

    ciclo:
    MOV eax,[esi]
    XCHG eax,[esi+4]
    MOV [esi],eax

    add esi, TYPE array
    add esi, TYPE array

    loop ciclo
    ret
    END start