//----------------------------------------------------------------
//	leapyear.s
//	
//	This program determines whether or not a year, specified 
//	by the user as a command-line argument, is a "leap" year
//	in case it occurs in the 21st Century (i.e., 2001-2099).
//
//	 assemble using:  $ as leapyear.s -o leapyear.o
//	 and link using:  $ ld leapyear.o base10io.o -o leapyear
//
//	programmer: <your name>
//	completion: 01 MAR 2006
//----------------------------------------------------------------

	.section	.data
year:	.int	2006			# default-value for year
msg0:	.ascii	"your year falls outside the 21st century\n"
len0:	.int	. - msg0
msg1:	.ascii	"xxxx is a leap year\n"
len1:	.int	. - msg1
msg2:	.ascii	"xxxx is not a leap year\n"
len2:	.int	. - msg2

	.section	.text
_start:	# check for the presence of a command-line argument
	cmpl	$1, (%esp)		# argument is missing?
	je	argok			# yes, use our default

	# convert argument to a number, and save it as 'year'
	<your code goes here>

	# verify that year falls within the 21st century
	cmpl	$2001, year		# year preceeds 2001?
	jb	not21			# yes, year not valid
	cmpl	$2099,year		# year follows 2099?
	ja	not21			# yes, year not valid

argok:	# now determine if the year is divisible by 4
	<your code goes here>

	# and branch to display the appropriate message 
	<your code goes here>

isleap:	# insert year in message 1 and write it to the display
	<your code goes here>
	jmp	exit 			# terminate program

noleap:	# insert year in message 2 and write it to the display 
	<your code goes here>
	jmp	exit 			# terminate program

not21:	# show the error-message 
	<your code goes here>

exit:	# terminate this program
	<your code goes here>

	.end				# no more to assemble