DA-OS/bootloader.asm at master · Auxburger/DA-OS · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
BITS 16

start:
    mov ax, 07C0h         ; Set up 4K stack space after this bootloader
    add ax, 288           ; (4096 + 512) / 16 bytes per paragraph
    mov ss, ax
    mov sp, 4096

    mov ax, 07C0h         ; Set data segment to where we're loaded
    mov ds, ax


    mov si, text_string   ; Put string position into SI
    call print_string     ; Call our string-printing routine

    jmp $                 ; Jump here - infinite loop!


    text_string db 'This is my new OS lul', 0


print_string:             ; Routine: output string in SI to screen
    mov ah, 0Eh           ; int 10h 'print char' function

.repeat:
    lodsb                 ; Get character from string
    cmp al, 0
    je .done              ; If char is zero, end of string
    int 10h               ; Otherwise, print it
    jmp .repeat

.done:
    ret


    times 510-($-$$) db 0 ; Pad remainder of boot sector with 0s
    dw 0xAA55             ; The standard PC boot signature