bits 16 ; boot sectors run in real mode
org 7c00h ; boot sector is loaded at 0x7c00
- mov dx, 0DEADh ; number to print
- mov cl, 0 ; column
- mov ch, 0 ; row
- call print_word
- mov dx, 0BEEFh
- mov cl, 0
- mov ch, 1
+_start
+ mov [boot_drive], dl ; BIOS sets dl to number of boot drive, we don't want to forget this
+
+ mov bp, 8000h ; Move the stack away
+ mov sp, bp
+
+ push cs
+ pop es
+ mov bx, 9000h ; Load at 0000:9000
+ mov dh, 2 ; Load 5 sectors
+ mov dl, [boot_drive] ; Load from boot drive
+ call read_sectors
+
+ mov dx, [9000h] ; Print value at 9000h, should be 0xDEAD
+ call print_word
+ mov dx, [9000h + 512] ; Print value at 9200h, should be 0xBEEF
call print_word
- jmp $
+ jmp $ ; Endless loop
%include "print.s"
+%include "disk.s"
+
+boot_drive resb 1 ; Reserve 1 byte for boot drive number
+
+times 510-($-$$) db 0 ; fill with 0 until 0x1fc is reached
+dw 0AA55h ; BIOS MBR signature
- times 510-($-$$) db 0 ; fill with 0 until 0x1fc is reached
- dw 0AA55h ; BIOS MBR signature
+times 256 dw 0DEADh ; Fill in 2nd sector with 0xDEAD
+times 256 dw 0BEEFh ; Fill in 3rd sector with 0xBEEF