H2 ex 4

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 db 20
    b db 3
    c dw 2
    e dd -444
    x dq 43
    v1 resq 1

; our code starts here
segment code use32 class=code
    start:
        ;(a-2)/(b+c)+a*c+e-x; a,b-byte; c-word; e-doubleword; x-qword Signed

        mov eax,0
        mov ecx,0
        mov al,[b];al=b
        cbw;ax=b
        mov cx,[c];cx=c
        add cx,ax;cx=b+c
        mov eax,0
        mov al,[a]
        sub al,2;al=a-2
        cbw
        cwd
        idiv cx
        cwde
        mov ebx,eax;ebx=(a-2)/(b+c)
        mov eax,0
        mov al,[a]
        cbw
        cwd
        imul word[c];dx:ax=a*c
        shl eax,16
        mov ax,dx
        rol eax,16
        ;we converted dx:ax to eax
        add eax,ebx;eax=(a-2)/(b+c)+a*c
        add eax,[e]
        ;eax=(a-2)/(b+c)+a*c+e
        cdq
        sub eax,dword[x+0]
        sbb edx,dword[x+4];edx:eax=(a-2)/(b+c)+a*c+e-x
        mov [v1+0],eax
        mov [v1+4],edx
        ;we assigned v1 the value of the expresion
        ; exit(0)
        push    dword 0      ; push the parameter for exit onto the stack
        call    [exit]       ; call exit to terminate the program