[   bits 16]           ; tell assembler that working in real mode(16 bit mode)
[org 0x7c00]        ; organize from 0x7C00 memory location where BIOS will load us

start:              ; start label from where our code starts
xor ax,ax           ; set ax register to 0
mov ds,ax           ; set data segment(ds) to 0
mov es,ax           ; set extra segment(es) to 0
mov bx,0x8000

push dx

mov ax,0x13         ;clears the screen
int 0x10            ;call bios video interrupt


mov ah,02           ;clear the screen with big font
int 0x10            ;interrupt displayt

; cursor position
mov al, 2
mov ah, 0
mov bl, 4
mov bh, 0
int 0x10
mov si, command_prompt
call print_string

mov ax,0x00         ; get keyboard input

int 0x16            ; interrupt for hold & read input

; load second sector into memory

mov ah, 0x02                    ; load second stage to memory
mov al, 1                       ; numbers of sectors to read into memory
pop dx
; mov dl, 0x80                    ; sector read from fixed/usb disk
mov ch, 0                       ; cylinder number
mov dh, 0                       ; head number
mov cl, 2                       ; sector number
mov bx, _OS_Stage_2             ; load into es:bx segment :offset of buffer
int 0x13                        ; disk I/O interrupt

jmp _OS_Stage_2                 ; jump to second stage

int 0x19

print_string:
    mov ah, 0x0E            ; value to tell interrupt handler that take value from al & print it

.repeat_next_char:
    lodsb                ; get character from string
    cmp al, 0                    ; cmp al with end of string
    je .done_print               ; if char is zero, end of string
    int 0x10                     ; otherwise, print it
    jmp .repeat_next_char        ; jmp to .repeat_next_char if not 0

.done_print:
    ret                         ;return


command_prompt db "myos", 0

; boot loader magic number
times ((0x200 - 2) - ($ - $$)) db 0x00     ;set 512 bytes for boot sector which are necessary
dw 0xAA55                                  ; boot signature 0xAA & 0x55


_OS_Stage_2:

mov al,2                    ; set font to normal mode
mov ah,0                    ; clear the screen
int 0x10                    ; call video interrupt

mov si, statement
call print_string

haltloop:
sti
hlt
jmp haltloop

statement db "ok", 0

; add how much memory we need
times (1024 - ($-$$)) db 0x00