Correct h2 ex1

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
    ;a - byte, b - word, c - double word, d - qword - Unsigned representation
    ;(c-a) + (b - d) +d = c-a+b
    a db 2
    b dw 10
    c dd 15
    d dq 5
    v1 resd 1
; our code starts here
segment code use32 class=code
    start:
        ; ...
        mov eax,0
        mov ebx,0
        mov ecx,0
        mov edx,0
        mov eax,[c]
        mov bx,[b]
        mov cl,[a]
        sub bx,cx
        add eax,ebx
        ; exit(0)
        push    dword 0      ; push the parameter for exit onto the stack
        call    [exit]       ; call exit to terminate the program