# string.s -- Program that reads a string, and then
# prints it out.  We will finish a modification that makes
# all the letters capital.
# 
# A string is simply an array of characters (bytes).
#
# Purpose of registers:
# $s0 = base address of string
# $s1 = offset into string 
# $s2 = total address
# $s3 = holds single character from string
# $s4 = ASCII value of newline character (10)

	.data
string:		.space 80	# make room for 80 character string
prompt:		.asciiz "Please enter some text:  "
out_str:	.asciiz "Your string is:  "
newline:	.asciiz "\n"

	.text
main:
	la $s0, string		# initialize base address of string
	li $s4, 10		# ascii value of '\n' is 10

	li $v0, 4		# print the prompt
	la $a0, prompt
	syscall

	li $v0, 8		# specify input-string function
	move $a0, $s0		# set $a0 to base address of string
	li $a1, 80		# tell machine to accept up to 80 chars
	syscall

	li $s1, 0

loop:
	add $s2, $s0, $s1	# compute address of character in array
	lb $s3, 0($s2)		# load single character into $s3
	beq $s3, $s4, end_loop
	
	li $v0, 1		# print integer value of $s3
	move $a0, $s3
	syscall

	li $v0, 4		# print newline
	la $a0, newline
	syscall

	addi $s1, $s1, 1	# point to next character in string
	j loop

end_loop:
	li $v0, 4		# introduce the output
	la $a0, out_str
	syscall

	li $v0, 4		# print the string
	move $a0, $s0
	syscall

	li $v0, 4		# print a newline
	la $a0, newline		
	syscall

	li $v0, 10		# end of program
	syscall