title: Square bracket notation around variable in cmd / DOS batch scripts
body: <p>I've seen cmd batch scripts using square notation to surround a variable. For example:</p>
  
  <pre><code>@echo off
  if [%1]==[] (
  echo no parameter entered
  ) else (
  echo param1 is %1
  )
  </code></pre>
  
  <p>What is the purpose of this?</p>