H3

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)
;Given the words A and B, compute the byte C as follows:
;the bits 0-5 are the same as the bits 5-10 of A
;the bits 6-7 are the same as the bits 1-2 of B.
;Compute the doubleword D as follows:
;the bits 8-15 are the same as the bits of C
;the bits 0-7 are the same as the bits 8-15 of B
;the bits 24-31 are the same as the bits 0-7 of A
;the bits 16-23 are the same as the bits 8-15 of A.
segment data use32 class=data
    ; ...
    a dw 01001011111001111b
    b dw 01011110010101100b
    c resb 1
    d resd 1
; our code starts here
segment code use32 class=code
    start:
        ; ...
        ;a)
        ;1)
        mov eax,0
        mov ebx,0
        mov ecx,0
        mov ax,[a]
        and ax,011111100000b
        shr ax,5;the bits 5-10 from a are stored in ax
        ;2)
        mov bx,[b]
        and bx,0110b;we get bits 1-2
        shl bx,5
        or ax,bx; we get the value for c in al
        mov [c],al
        ;b)we also create the value of d in eax
        ;1)
        shl ax,8;move the bits from c to the position 8-15
        ;2)
        mov ebx,0
        mov bx,[b]
        and bx,01111111100000000b
        shr bx,8
        or ax,bx;the lower part of d is in ax
        ;3)we just move a in cx and rotate it and then move it to the extended
        mov cx,[a]
        ror cx,8
        shl ecx,16
        or eax,ecx
        mov [d],eax







        ; exit(0)
        push    dword 0      ; push the parameter for exit onto the stack
        call    [exit]       ; call exit to terminate the program