Pretty new to assembly language and I need help with this problem. I'm trying to traverse through a string and see if each character is either a number or a operand (+, -, *, /). Everytime I run the program, it doesn't work properly. I'm pretty sure the error is in the 'lb' line after my loop label but I can't figure out what is wrong. Any help would be greatly appreciated. Thank you.
.data
string1: .asciiz "Please enter a string. Make sure the string only contains RPN characters: "
string2: .asciiz "Invalid input: "
string3: .asciiz "Input is valid.\n"
string4: .asciiz "The first operator is "
string5: .asciiz "No operator found.\n"
string6: .asciiz "Please enter a single interger: \n"
string7: .asciiz "Please enter a single operator (+,-,*,/): \n"
string8: .asciiz "The result is "
input: .space 50
output: .space 3
.text
.globl Olu
Olu:
la $a0, string1
li $v0, 4
syscall
la $a0, input
li $v0, 8
syscall
move $s0, $a0 #address of input
loop:
lb $t0, ($s0) # gets a character
beq $t0, $zero, next # runs loop till 0 is received
blt $t0, 48, charCheck # checks if char is less than 0
bgt $t0, 57, notValid # checks if char is greater than 9
add $s0, $s0, 1 # moves along string
j loop
notValid:
la $a0, string2
li $v0, 4
syscall
move $a0, $t0
li $v0, 11
syscall
j next
charCheck:
bne $t0, 42, notValid #checks if char is equal to op
bne $t0, 43, notValid
bne $t0, 45, notValid
bne $t0, 47, notValid
add $s0, $s0, 1
j loop
next:
li $v0, 10
syscallAlso, if anyone knows of a decent MIPS simulator/debugger, please let me know. Thanks again!