Simple bare-metal "Hello world" program

gistfile1.asm

/*
 * Compile with
 *
 * as --32 -o vga.o vga.s && objcopy -Obinary vga.o vga.bin
 *
 */

	.arch i386
	.text
	.code16
	.org 0

start:
	/* Fix segment registers so that local labels work */
	ljmp	$0x7c0, $1f
1:	push	%cs
	popw	%ds
	push	%cs
	popw	%es
	push	%cs
	popw	%ss
	/* Set up 16kB stack.  Must do this immediately after loading %ss */
	movw	$0x4000, %sp

	/* Set up %fs for access to VGA memory */
	movw	$0xb800, %ax
	movw	%ax, %fs

	/* Write "Hello!" to start of VGA memory */
	movw	$( 0xc700 | 'H' ), %fs:0
	movw	$( 0xc700 | 'e' ), %fs:2
	movw	$( 0xc700 | 'l' ), %fs:4
	movw	$( 0xc700 | 'l' ), %fs:6
	movw	$( 0xc700 | 'o' ), %fs:8
	movw	$( 0xc700 | '!' ), %fs:10

	/* Hang system */
1:	cli
	hlt
	jmp	1b