hw2.asm

.data
   prompt1: .asciiz "Please enter a positive number: "
   incorrectPrompt: .asciiz "Invalid number, please try again.\n" 
   prompt2: .asciiz "The "
   prompt3: .asciiz " fib number is: "
   newLine: .asciiz "\n"
.text
    la $a0, prompt1
    la $a1, incorrectPrompt
    jal readNonNegInt
    move $a0, $v0
    move $s0, $v0
    jal fib
    move $s1, $v0
    la $a0, prompt2
    move $a1, $s0
    jal printInt
    la $a0, prompt3
    move $a1, $s1
    jal printInt
    j exit
    fib:
    	bgt $a0, 1, rec #if it is 1 or 0 it is just that number for the fib #
    	move $v0,  $a0
    	jr $ra
    rec:
        addi $sp, $sp, -12
        sw $ra, 0($sp) #put the return address on the stack
        sw $a0, 4($sp) #put the value of $a0 on the stack
        addi $a0, $a0, -1
        jal fib
        sw $v0, 8($sp) #put the result of the first recursive method on the stack
        addi $a0, $a0, -1
        jal fib
        lw $t0, 8($sp) #restore the result for the first recursive method
        add $v0, $t0, $v0 #add them together
		#restore from the stack
		lw $ra, 0($sp)
        lw $a0, 4($sp)
        addi $sp, $sp, 12 #update stack pointer
        jr $ra #return :)
    exit: li $v0, 10
        syscall
    readInt: li $v0, 4
        syscall
        li $v0, 5 # Set to read an int
        syscall
        jr $ra # return
    readNonNegInt: add $s0, $ra, $zero
        jal readInt # call readInt
        move $ra, $s0
        bltz $v0, incorrect # if it is a negative number reprompt
        jr $ra # return
      incorrect: move $t0, $a0 # Save the $a0 var for calling readNonNegInt
        move $a0, $a1 # prep to write the incorrect prompt
        li $v0, 4 # prep to write a string
        syscall
        move $a1, $a0
        move $a0, $t0
        j readNonNegInt
    printInt: li $v0, 4 # prep the syscall for a print string
        syscall 
        move $a0, $a1 # load the int we are trying to print
        li $v0, 1 # get ready to print it.
        syscall
        jr $ra #return