We love complicated solutions

[bits 16]               ;protected mode
[org 0x7c00]    ;bootloader base - loaded by kernel

        ;set ds to 0
        mov ax, 0x0000
        mov ds, ax

        ; set ss and sp
        mov ss, ax
        mov sp, ax
        nop

        ;init print colors
        mov ah, 0x0e
        mov bh, 0x00

        mov si, msg ;set hello world message in si
        call printstring

        jmp $ ;hang

printstring:

.next_char:
        mov al, [si]    ;load current character in string
        or al, al               ;see if al is zero
        jz .char_done   ;if al is zero, jump to end (end of string reached)
        call change_attr
        int 0x10                ;call print character command
        inc si                  ;increase si, next character
        jmp .next_char

.char_done:
        ret

change_attr:
        push ax
        push bx
        push cx
        push dx
        push di
        push ds

        ; get cursor location
        mov ah, 03h
        mov bh, 00h
        int 10h

        ; calculate the location of attr byte
        mov al, 80
        mul dh      ; AX = 80*ROW
        mov dh, 0
        add ax, dx  ; AX = 80*ROW + COL
        shl ax, 1   ; AX = 2*(80*ROW + COL)
        inc ax      ; AX = 2*(80*ROW + COL) + 1

        ; now ax contains location of attr inside 0xb800
        mov di, ax
        mov ax, 0b800h
        mov ds, ax
        mov al, 04h
        mov [di], al

        ; restore context
        pop ds
        pop di
        pop dx
        pop cx
        pop bx
        pop ax

        ; return
        ret


;data section - never reaced
msg db 'hello mostafa :P', 13, 10, 0

times 510 - ($ - $$) db 0       ;fill rest of file (needs a size of 512 bytes)
dw 0xaa55 ;end