title: Isolating 4 bits in a 32 bit number in MIPS
body: <p>I'm new to MIPS and I'm trying to find out whether I can actually send in 4 bits
  to a MIPS function using $a0, for example, or whether I have to send a 32-bit number
  and just use the convention that the first 4 bits of that number are the 4 bits of interest.</p>
  
  <p>Since the registers only store 32-bit words, I'm assuming you have to provide a 32-bit word,
  but if it's not necessary I would really like to know how to avoid it.</p>
  
  <p>Thanks!</p>