org 0x7c00 ; Loaded at address 0x7c00 by BIOS.

CR equ 0x0d
LF equ 0x0a

; http://en.wikipedia.org/wiki/BIOS_color_attributes
black equ 0x00
blue equ 0x01
green equ 0x02
cyan equ 0x03
red equ 0x04
magenta equ 0x05
brown equ 0x06
light_grey equ 0x07
dark_grey equ 0x08
light_blue equ 0x09
light_green equ 0x0a
light_cyan equ 0x0b
light_red equ 0x0c
light_magenta equ 0x0d
yellow equ 0x0e
white equ 0x0f

start:
    jmp main

print:
    lodsb
    or al, al
    jz print_end
    mov ah, 0x0e
    mov bl, white
    int 0x10
    jmp print

print_end:
    ret

switch_to_mode_0x12: ; VGA 640x480 16
    ; http://en.wikipedia.org/wiki/INT_10H
    ;   Set video mode
    ;   AH=00h
    ;   AL = video mode
    xor ah, ah
    mov al, 0x12
    int 0x10
    ret

main:
    xor ax, ax ; Set DS register to zero
    mov ds, ax ; because we set org to 0x7c00
    cld

    ; http://en.wikipedia.org/wiki/INT_10H
    ;   Teletype output
    ;   AH=0Eh
    ;   AL = Character
    ;   BH = Page Number
    ;   BL = Color (only in graphic mode)
    ;
    ; Need to switch to a graphic mode.
    ; http://www.wagemakers.be/english/doc/vga lists mode 0x12 as a graphic mode.
    call switch_to_mode_0x12

    ; http://en.wikipedia.org/wiki/INT_10H
    ;   Set background/border color
    ;   AH=0Bh,
    ;   BH = 00h
    ;   BL = Background/Border color (border only in text modes)
    mov ah, 0x0b
    xor bh, bh
    mov bl, white
    int 0x10

    mov si, msg
    call print

    cli
    hlt

msg db 'Hello', CR, LF, '-----', 0

times 512-($-$$) db 0