title: Issues with MIPS jump
body: <p>I'm still new to MIPS and I'm confused as to what is going wrong. Im testing in QTSpim. It's telling me "Unknown System Call:-1000". I'm a little confused as to whats going wrong. Im using -1000 in the console to jump into op to set my operand(building a simple integer calculator).</p>
  
  <pre><code>li $s7, 5   #Read a Character AS A INT and store in $s7
  syscall
  
  #Load values for each:
  li $t0, 43 #Addition
  li $t1, 45 #Subtraction
  li $t2, 42 #Multiplication
  li $t3, 47 #Division
  
  #if $s7 is equal to any of these, then jump back to the main loop and wait for a second operand
  beq $s7, $t0, loop #ADD
  beq $s7, $t1, loop #SUB
  beq $s7, $t2, loop #MULTI
  beq $s7, $t3, loop #DIV
  
  la $a0, error #Load error message
  j ra
  </code></pre>