lab6demo.asm

.data
en: 	.asciiz "n = "
eol: 	.asciiz "\n"
.text
 
 
main: 
	la 	$a0, en # print "n = "
	li 	$v0, 4 	#
	syscall 	#
	li $v0, 5 	# read integer
	syscall 	#
	move $a0, $v0 	# $a0 = $v0
	jal fac 	# $v0 = fib(n)
	add $a0,$v0,$zero
li $v0,1
syscall

li $v0,10
syscall

 #base case 
fac: 
	bne 	$a0, $zero, gen # if $a0 != 0, goto generic case
	ori 	$v0, $zero, 1 	# else set result $v0 = 1
	jr 	$ra 		# return
#recursive case
gen:
	addiu 	$sp, $sp, -8 	# make room for 2 registers on stack
	sw 	$ra, 4($sp) 	# save return address register $ra
	sw 	$a0, 0($sp) 	# save argument register $a0=n
	
	addiu 	$a0, $a0, -1 	# $a0 = n-1
	jal fac 		# $v0 = fac(n-1)
		
	lw 	$a0, 0($sp) 	# restore $a0=n
	lw 	$ra, 4($sp) 	# restore $ra
	addiu 	$sp, $sp, 8 	# multipop stack
		
	mul 	$v0, $v0, $a0 	# $v0 = fac(n-1) x n
	jr 	$ra