SE 3340: Computer Architecture - Homework 3

homework3.asm

.data
	prompt:			.asciiz	"Input some text dude"
	charactersMessage:	.asciiz	"Characters: "
	wordsMessage:		.asciiz	"Words: "
	input:			.space	100
	newLine:		.asciiz	"\n"

.text
	# prompts for the text to analyze
	li	$v0,	54
	la	$a0,	prompt
	la	$a1,	input
	li	$a2,	100
	syscall
	
	la	$t0,	input # store the text to analyze in $t0
	li	$t1,	0x20 # store the space character in $t1
	
	li	$v0,	-1 # makes $v0, the number of characters, initally equal to -1 to ignore the new line character
	li	$v1,	1 # makes $v0, the number of words, initially equal to 1 to account for the last word in an input
	
	jal	count # calls the count function
	
	la	$s0,	($v0) # loads the number of characters to $s0
	la	$s1,	($v1) # loads the number of words to $s1
	
	bne	$s0,	-1,	printInput
	# handles the case in which an empty string is given
	li	$s0,	0 # set the characters to 0
	li	$s1,	0 # set the words to 0
	
	printInput:
		# prints the input that was analyzed
		li	$v0,	4
		la	$a0,	input
		syscall
	
	printWords:
		# prints the message "Characters: "
		li	$v0,	4 
		la	$a0,	charactersMessage
		syscall
	
		# prints the amount of characters in the input text
		li	$v0,	1
		la	$a0,	($s0)
		syscall
	
		# prints a new line character
		li	$v0,	4
		la	$a0,	newLine
		syscall
		
	printLetters:
		# prints the message "Words: "
		li	$v0,	4
		la	$a0,	wordsMessage
		syscall
	
		# prints the amount of words in the input text
		li	$v0,	1
		la	$a0,	($s1)
		syscall
	
	# ends the program
	li	$v0,	10
	syscall
	
	count:
		lb	$a0,	($t0) # stores the single byte we are analyzing into $a0
  		beqz	$a0,	exit # if we reach a zero character, then we are done analyzing the input, so exit
  			
  		# stores our current PC memory location in the $sp (stack pointer) to refer back to the previous 
  		# location we wish to go back to if we do, in fact, traverse to the countword function
  		addi	$sp,	$sp,	-4
		sw	$ra,	($sp)
  		
  		# if we encounter a space character, count the word using the countword function
  		bne	$a0,	$t1,	continue
  		jal	countword

  		continue:
  			# restores the $ra that was cached from the $sp
  			lw	$ra,	($sp)
  			addi	$sp,	$sp,	4
  			
  			addi	$v0,	$v0,	1 # increments the letter counter
  			addi	$t0,	$t0,	1 # increments the byte being read from the input
  			j	count # loop back to counting
  			
  		exit:
  			jr	$ra # jumps back to where we came from

  		countword:
  			addi	$v1,	$v1,	1 # increments the word counter
  			jr	$ra # jumps back from where we came from