Add boot.asm

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heckeralt 2024-09-21 14:09:44 -04:00
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; boot.asm - A simple bootloader example
[bits 16] ; Set to 16-bit mode
[org 0x7C00] ; BIOS loads the bootloader at this address
start:
; Clear screen
mov ax, 0x0003 ; Set video mode to 3 (80x25 color text)
int 0x10 ; BIOS interrupt to set video mode
; Print "Hello, World!"
mov si, hello_message ; Load address of the message into SI
call print_string ; Call function to print the string
; Hang the system (infinite loop)
hang:
jmp hang ; Jump to hang indefinitely
; Function to print a string
print_string:
mov ah, 0x0E ; BIOS teletype output function
.next_char:
lodsb ; Load byte at DS:SI into AL and increment SI
cmp al, 0 ; Check for null terminator
je .done ; If null, we are done
int 0x10 ; Call BIOS to print character in AL
jmp .next_char ; Repeat for next character
.done:
ret ; Return from function
; Data section
hello_message db 'Hello, World!', 0 ; Null-terminated string
; Bootloader signature (must be present)
times 510 - ($ - $$) db 0 ; Fill the rest of the sector with zeros
dw 0xAA55 ; Boot signature