palindrome.asm

# check if user provided string is palindrome

.data

welcomeMsg: .asciiz "Enter a string: "
userString: .space 256
newline: .asciiz "\n"
yes: .asciiz "IS PALINDROME"
no: .asciiz "NOT PALINDROME"

.text

main:
	li $v0, 4
	la $a0, welcomeMsg
	syscall
	la $a0, userString
	li $a1, 256
	li $v0, 8
	syscall

	li $v0, 4
	la $a0, userString
	syscall
	lb $t5, newline

	# store address of last element of userString in $a1
	add $t1, $a0, $zero 
	lengthZero:
		lb $t3, ($t1)
		addi $t1, $t1, 1
		beq $t3, $t5, done # this step is required as MIPS reads newline after string	
		bne $t3, $zero, lengthZero
	done: 
	addi $t1, $t1, -2
	# check if palindrome
	add $t0, $a0, $zero
	
	check_letter:
		lb $t2, ($t0)
		lb $t3, ($t1)
		bne $t2, $t3, notPalindrome
		addi $t0, $t0, 1
		addi $t1, $t1, -1
		blt $t0, $t1, check_letter

	li $v0, 4
	la $a0, yes
	syscall
	j endProgram

	notPalindrome:
		li $v0, 4
		la $a0, no
		syscall
	endProgram:
	li $v0, 10
	syscall