title: Why is Set on Less Than an ALU operation
body: <p>Why is <code>slt</code> considered an ALU operation? I thought it will just do a subtract then get the *<em>Z</em>*ero output from ALU?</p>
  
  <pre>
   ALU control lines |     Function
  -------------------+-------------------
         0000        |       AND
         0001        |       OR
         0010        |       add
         0110        |     subtract
         0111        | set on less than
  </pre>
  
  <p>Or is the ALU supposed to output 1 if the result of <code>A - B</code> (in <code>slt $t1, A, B</code>) is negative. </p>