H2 ex 2

bits 32 ; assembling for the 32 bits architecture

; declare the EntryPoint (a label defining the very first instruction of the program)
global start

; declare external functions needed by our program
extern exit               ; tell nasm that exit exists even if we won't be defining it
import exit msvcrt.dll    ; exit is a function that ends the calling process. It is defined in msvcrt.dll
                          ; msvcrt.dll contains exit, printf and all the other important C-runtime specific functions

; our data is declared here (the variables needed by our program)
segment data use32 class=data
    ; ...c+a+b+b+a
    ;a - byte, b - word, c - double word, d - qword - Signed representation
    a db -2
    b dw -5
    c dd 200
    d dq -5000
    v1 resq 1

; our code starts here
segment code use32 class=code
    start:
        ; ...

        mov eax,0
        mov al,[a]
        cbw
        add ax,[b]
        add ax,[b]
        cwde
        add eax,[c]
        mov edx,0
        cdq
        add eax,dword[d+0]
        add edx,dword[d+4]
        mov dword[v1+0],eax
        mov dword[v1+4],edx
        ; exit(0)
        push    dword 0      ; push the parameter for exit onto the stack
        call    [exit]       ; call exit to terminate the program