# Sum.asm
#
# Author : Archana Chidanandan, 12/09/2003
#
# This program calculates the sum of the first N integers.
#
# This program demonstrates the use of procedures using the "jal" and "jr" instructions.
#
# NOTE : THIS PROGRAM DOES NOT ADHERE TO THE MIPS REGSITERS CONVENTIONS
#
# Modify the program so that it adheres to the MIPS register conventions.
#


	.text
	.globl main
      .globl SumCal
      .globl loop
      .globl exit

main:
	la	$t0, N		
	lw	$t0, 0($t0)	      # Load the value of N

	jal     SumCal		# Call method "SumCal"
	
	la	$t0, SumOfN
	sw	$t3, 0($t0)	      # Store sum of first 
					# N integers to memory

	li	$v0, 10		# Prepare to Exit
	syscall			# End of program



SumCal:				# Procedure to calculate 
					# sum of first N integers
	li 	$t2, 0		# i = 0
	li	$t3, 0  	      # Sum = 0
loop:
	beq	$t2, $t0, exit    # if ( i == N ), quit
	addi	$t2, $t2, 1	      # i = i + 1
	add	$t3, $t3, $t2	# Sum = Sum + i
	j 	loop
exit:
	jr	$ra		# Return to calling program


	.data
N:		.word  3
SumOfN :	.word  0