palindrome:
        # save $ra
        addi $sp, $sp, -4
        sw $ra, 0($sp)
        addi $t0, $0, 0
        move $t1, $a0
        addi $t2, $a0, 1
        loop:
            # get character at $t1
            lb $t3, 0($t1)

            # check if character is null
            beq $t3, $zero, end

            # get character at $t2
            lb $t4, 0($t2)

            # check if character is null
            beq $t4, $zero, end

            # check if characters are equal
            bne $t3, $t4, not_palindrome

            # increment $t1 and $t2
            addi $t1, $t1, 1
            addi $t2, $t2, -1

            # loop
            j loop

        # not a palindrome
        not_palindrome:
            addi $t0, $zero, 0

        # end of string
        end:
            # set $v0 to $t0
            move $v0, $t0

            # restore $ra
            lw $ra, 0($sp)
            addi $sp, $sp, 4

            # return
            jr $ra