first.s

//----------------------------------------------------------------
//	first.s: Output "Welcome to Assembly World."
//
//	compile using:	$ as first.s -o first.o
//	link using:	$ ld first.o -o first
//	execute using:	$ ./first
//
//----------------------------------------------------------------

	.section	.data
msg:	.string	"Welcome to Assembly World.\n"	# the output message
        len = . - msg		# the length of the message

	.section	.text
_start:	movl	$4, %eax	# system-call number for sys_write 
	movl	$1, %ebx	# device-file id-number for stdout
	movl	$msg, %ecx	# address of the message string
	movl	$len, %edx	# length of the message string
	int	$0x80		# trap-instruction for system-call

	movl	$1, %eax	# system-call number for sys_exit
	movl	$0, %ebx	# value for the exit-code 
	int	$0x80		# trap-instruction for system-call

	.globl	_start		# makes entry-point visible (can omit this)